Edible fats and oils : their composition, manufacture and analysis

By Simmons et al.

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Title: Edible fats and oils
their composition, manufacture and analysis

Author: W. H. Simmons
C. Ainsworth Mitchell

Release date: September 5, 2026 [eBook #79516]

Language: English

Original publication: London: Scott, Greenwood & Son, 1911

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EDIBLE FATS AND OILS

THEIR COMPOSITION, MANUFACTURE AND ANALYSIS

BY
W. H. SIMMONS, B. SC.(LOND.), F.C.S.

LECTURER ON SOAP MANUFACTURE AT THE BATTERSEA POLYTECHNIC
AND JOINT AUTHOR OF THE “HANDBOOK OF SOAP MANUFACTURE”
AND
C. AINSWORTH MITCHELL, B.A.(OXON.), F.I.C.

JOINT AUTHOR OF “FIBRES USED IN TEXTILE AND ALLIED INDUSTRIES”

LONDON
SCOTT, GREENWOOD & SON
“THE OIL AND COLOUR TRADES JOURNAL” OFFICES
8 BROADWAY, LUDGATE, E.C.
1911

[_All Rights Reserved_]

PREFACE

The importance of a due proportion of fat in the diet of man is
insisted on by all physiologists, and the variety of forms in which
fat enters into human food is very considerable. Formerly butter,
lard, and dripping were the principal fats consumed as food, but the
introduction of margarine by M. Mège-Mouries in 1872, followed, in more
recent years, by the discovery of large quantities of new vegetable
fats and oils, and of greatly improved processes for their preparation,
purification, and refinement, has much augmented and cheapened the
supply of fat for human consumption.

The popular prejudice against artificial butters has now been largely
dissipated, and the edible fat and oil industry has become an important
one.

The aim of the present volume is to describe, in a concise manner,
the properties of the different edible fats and oils and their
combinations, and to give an outline of the modern processes used in
their preparation and purification.

Unfortunately the discoveries of science in this, as in other branches
of technical chemistry, have led to the practice of a considerable
amount of very skilful adulteration, and it is hoped that the somewhat
lengthy chapter on the analysis of edible food products will be useful
to those engaged in the industry in enabling such adulteration to be
detected and successfully combated.

W. H. S.
C. A. M.
LONDON, _April 1911_.

CONTENTS

CHAPTER I PAGE
INTRODUCTION 1
Fat as Food—Physiological Considerations—Constitution
of Fats and Oils.

CHAPTER II
RAW MATERIALS USED IN THE MANUFACTURE OF EDIBLE FATS
AND OILS 14

CHAPTER III
REFINING, BLEACHING, AND DEODORISING FATS AND OILS 23
Physical Methods—Washing, freezing, filtration,
treatment with charcoal and fuller’s earth, steaming.
Chemical methods—Caustic soda, sodium carbonate and
silicate, alkaline earths, ozone, hydrosulphites,
sodium bisulphite, organic peroxides.

CHAPTER IV
BUTTER 39

CHAPTER V
LARD 56

CHAPTER VI
MARGARINE AND OTHER BUTTER SUBSTITUTES 65
Margarine, Oleomargarine, or Artificial
Butter—Invention and Development—Modern Processes
and Formulæ—Vegetable Butter.

CHAPTER VII
SALAD OILS 74

Salad Oils—Oils used for Culinary and Confectionery
Purposes—Chocolate Fats.

CHAPTER VIII
ANALYSIS OF RAW MATERIALS AND FINISHED PRODUCTS 89
General Methods of Analysis of Fats and Oils—Special
Tests for Individual Oils—Analysis of Butter,
Margarine, Lard, Cheese, Chocolate.

CHAPTER IX
STATISTICS OF THE TRADE IN EDIBLE OILS 137

INDEX 145

EDIBLE FATS AND OILS

CHAPTER I

INTRODUCTION

Fat as Food—Physiological Considerations—Constitution of Fats and Oils.

The food of man may be divided broadly into two classes, _nitrogenous_,
or flesh-forming, which is almost entirely of animal origin, and
_carbonaceous_, or energy-producing, derived both from the animal and
vegetable kingdoms. Besides nitrogen and carbon, many other elements,
of course, such as phosphorus, calcium, iron, etc., normally enter into
the composition of human food, but the nitrogen and carbon constitute
the chief ingredients thereof, and are absolutely necessary to maintain
the body in a healthy and efficient state.

There is an almost infinite variety of forms in which carbon may be
taken into the stomach, but the vast majority of carbonaceous foods may
be classified in two great chemical families: (1) the _carbohydrates_,
comprising starch, sugar, and similar substances, which consist of
carbon, hydrogen, and oxygen, the two latter in quantities having the
same ratio as in water; and (2) the _oils and fats_, with which in the
present volume it is proposed to deal.

_Physiological Considerations._—The primary function of
carbon-containing food is, by its combustion, to produce heat or
other form of energy. The combustion of 1 gram of carbon to carbon
dioxide produces 8080 calories; of 1 gram of hydrogen to water, 34,462
calories; whilst the presence of oxygen actually reduces the calorific
value of the substance. Hence the higher the proportion of carbon, and
lower the amount of oxygen, the greater will be the heat-producing
power of a food; and since fats are much richer in carbon than starch
or sugar, containing about 2½ times as much, they constitute the most
concentrated form in which fuel can be supplied to the body. In the
case of animal fats, carbon in the form of carbohydrate is converted
into fat by the animal organism, and is thus rendered more suitable for
the food of man; as although man in his internal economy, principally
by means of his liver, is quite capable of himself transforming
starchy matter into fat, in so doing he expends a certain amount
of energy. Moreover, the human stomach is relatively smaller than
that of an animal, and therefore a more highly concentrated form of
carbon-containing food is desirable. Dripping is especially rich in
carbon, containing over 10 per cent. more than does butter or suet, and
it is regrettable that the use of dripping, formerly so popular among
the working classes, has now become so largely a thing of the past.

The average relative proportions of fat and carbohydrate in the food
of man vary with the climate, and are also governed to a considerable
extent by their availability. Thus in very hot regions carbohydrates
predominate, whilst in colder countries chiefly fat is consumed. The
Eskimo takes almost all his carbon in the form of oil and fat, whereas
the Indian or Chinese subsists mainly on carbohydrates. In this country
the proportions recommended by physiologists, though varying slightly,
are about 1 part of fat to 10 parts of carbohydrates, the amount of
fat desirable being slightly higher in winter than in summer.

Besides its value as a heat or energy producer, the presence of a
proportion of fat in human food is important in other ways, for the
“food value” of any substance depends not only upon its composition,
but also on its digestibility and palatability; and whilst fats are
much more readily assimilated than carbohydrates, they also render more
palatable, and assist in the digestion of, other articles of food.

Butter is the most easily digested of all fatty foods, and in
cases where a fat diet is necessary, up to ¼ lb. of butter can be
absorbed per diem. Margarine, which is usually made to approximate
fairly closely to butter in composition, except in so far as the
butter contains butyric and other volatile fatty acids, should be as
digestible as butter, and is almost universally agreed to be so.

Yet another useful purpose served by a proportion of fatty food
consists in facilitating the passage of masticated food to the stomach,
and of the refuse matter through the bowel.

_Constitution of Fats and Oils._—The difference between a fat and an
oil is entirely dependent upon temperature, a fat becoming an oil when
it is melted, and an oil a fat when solidified. The term _oil_ is used
for substances differing widely both in composition and properties, but
all the fats and oils used for edible purposes are of the same general
type of constitution, viz. esters or salts of glycerin with one or
more fatty acids, which are termed “glycerides.” Their composition was
first placed on a scientific basis by Chevreul, who in the early part
of the last century showed that when a fat, such as tallow or lard, was
converted into soap by the action of sodium or potassium hydroxide, the
fat was decomposed into glycerin and fatty acids, the latter combining
with the alkali to form the soap, while the glycerin, remaining free,
was separated in the lyes. The three most commonly occurring glycerides
are stearin and palmitin (of which tallow chiefly consists) and olein
(the principal constituent of olive oil), and the action of sodium
hydroxide on these may be represented by the following equations:—

CH₂OOC₁₈H₃₅ CH₂OH
/ /
CHOOC₁₈H₃₅ + 3NaOH = 3NaOOC₁₈H₃₅ + CHOH
\ \
CH₂OOC₁₈H₃₅ CH₂OH

(Stearin) (Sodium (Sodium (Glycerin)
hydroxide) stearate)
--------------------------------------------------------------------

CH₂OOC₁₆H₃₁ CH₂OH
/ /
CHOOC₁₆H₃₁ + 3NaOH = 3NaOOC₁₆H₃₁ + CHOH
\ \
CH₂OOC₁₆H₃₁ CH₂OH

(Palmitin) (Sodium (Sodium (Glycerin)
hydroxide) palmitate)
--------------------------------------------------------------------

CH₂OOC₁₈H₃₃ CH₂OH
/ /
CHOOC₁₈H₃₃ + 3NaOH = 3NaOOC₁₈H₃₃ + CHOH
\ \
CH₂OOC₁₈H₃₃ CH₂OH

(Olein) (Sodium (Sodium (Glycerin)
hydroxide) oleate)

The conclusions of Chevreul as to the composition of fats were
subsequently confirmed by Berthelot, who succeeded in producing the
glycerides synthetically by heating the fatty acids with glycerin under
pressure in sealed tubes. Heating together, for example, stearic acid
and glycerin, he obtained stearin, according to the equation:—

3 C₁₈H₃₅O₂H + C₃H₅(OH)₃ = C₃H₅(C₁₈H₃₅O₂)₂

In view of the fact that glycerin contains three hydroxyl (OH) groups
in which the H is displaceable by an acid radicle, it follows that
compounds may be formed, in which only one, or two, or all three of
the hydrogen atoms are replaced by an acid, compounds of the following
types resulting; where R represents a fatty acid radicle.

Monoglyceride:—
CH₂OR CH₂OH
| |
(Alpha) CHOH and (Beta) CHOR
| |
CH₂OH CH₂OH

Diglyceride:—
CH₂OR CH₂OR
| |
(Alpha) CHOH and (Beta) CHOR
| |
CH₂OR CH₂OH

Triglyceride:—
CH₂OR
|
CHOR
|
CH₂OR

Intermediate products, corresponding to the above formulæ for the mono-
and di-glycerides, were obtained by Berthelot in his syntheses, but in
natural oils and fats glycerides are only met with in which all the
hydrogen atoms in the hydroxyl groups are displaced by an acid.

Formerly it was believed that in nature the acid radicles combining
with the same molecule of glycerin were all identical, but during the
last few years a large number of so-called “mixed glycerides” have
been discovered in various oils and fats, which may be represented
by the above formula for the triglyceride, if the radicles denoted
by R are assumed to be not all alike. Among these mixed glycerides
may be mentioned oleodipalmitin, C₃H₅(OC₁₈H₃₃O)(OC₁₆H₃₁O)₂;
stearodipalmitin, C₃H₅(OC₁₈H₃₅O)(OC₁₆H₃₁O)₂; oleopalmitostearin,
C₃H₅(OC₁₈H₃₃O)(OC₁₆H₃₁O)(OC₁₈H₃₅O); and palmitodistearin, C₃H₅
(OC₁₆H₃₁O) (OC₁₈H₃₅O)₂ obtained by Hansen, and by Bömer from tallow;
stearodipalmitin being also found in goose and turkey fat by Klimont
and Meisels, and palmitodistearin in lard by Kreis and Hafner.

Oleodidaturin C₃H₅ (OC₁₈H₃₃O) (OC₁₇H₃₃O)₂ has been found in olive oil
by Holde and Stange to the extent of one to two per cent., and it is
probable that the butyric acid present in butter fat exists as a mixed
glyceride, and not as butyrin; indeed, mixed glycerides are claimed
to have been found in butter fat by Bell, and Blyth, and Harrison
respectively.

The following are the chief pure triglycerides, together with their
source, formulæ, and more important constants:—

It will be observed that butyrin and olein are both liquid at ordinary
temperatures, while tallow and palmitin have comparatively high
melting points. Fats such as tallow or palm oil, therefore, in which
the proportion of these latter is high, are firm and hard, the degree
of hardness increasing with the percentage of these glycerides.

_Butyrin_ (Tributyrin) may be obtained by heating together butyric acid
and glycerin under pressure. According to Scheij its specific gravity is

20° 60°
_d_ ———— = 1·0324, and _d_ ———— = 0·9963.
4 4

It is almost insoluble in water, and has an intensely bitter taste.

_Laurin_ (Trilaurin) may be produced by heating together lauric acid
and glycerin. It is readily soluble in ether, but only slightly so in
cold absolute alcohol, and crystallises in needles, melting at 45-46°
C., and having, according to Scheij, the specific gravity

60°
_d_ ———— = 0·8944.
4

_Myristin_ (Trimyristin) may be isolated from nutmeg butter by
fractional distillation in vacuo, or can be prepared by heating
together myristic acid and glycerin. It crystallises in laminæ, which
on heating first melt at 56°·5, but again solidify as the temperature
is further raised, at 57-58°. The product then has a melting-point of
45-55°. Its boiling point in vacuo is 290-300°, and its density

60°
_d_ ———— = 0·8848.
4

_Palmitin_ (Tripalmitin) may be prepared artificially by heating
together palmitic acid and glycerin, repeatedly boiling the product
with alcohol, and allowing it to crystallise, when greasy scales are
obtained, having a peculiar pearly appearance. The effect of heat on
palmitin is somewhat curious, indicating the existence of distinct
modifications. Thus when heated to 46° C. it liquefies, but again
becomes solid on further raising the temperature, melting once more at
61°·7, and becoming cloudy, with separation of crystalline particles.
Further increase of temperature to 63° C. renders the liquid clear, and
this temperature is regarded as the true melting-point. After melting
and re-solidifying, palmitin possesses no crystalline fracture.

_Stearin_ (Tristearin) may be separated from tallow by dissolving it
in ether and allowing it to crystallise, when small crystals separate,
having a bright pearly lustre. Stearin when heated also shows the
existence of two modifications. Thus, on raising the temperature
to 55° C., stearin liquefies, but again becomes solid on further
increasing the temperature until 71°·6 is reached, when it again melts.
If this liquid is further heated to 76°, and then allowed to cool,
solidification does not take place until the temperature has fallen to
55°, but if, after attaining 71°·6, it is immediately cooled, it will
solidify at 70° C.

_Olein_ (Triolein) is one of the most widely distributed natural
glycerides, and may be prepared in an impure form from olive oil by
separating the solid glycerides by cooling. After maintaining the
oil at a low temperature for several days, and separating the liquid
portion, the latter may be freed from traces of stearin and palmitin
by solution in alcohol. Olein may also be produced artificially
by heating together oleic acid and glycerin. It is an odourless,
colourless, and tasteless oil, which may be distilled _in vacuo_,
without decomposition, but which rapidly absorbs oxygen from the air,
and becomes rancid.

As already stated, the natural glycerides of which edible fats and oils
are composed, consist of combinations of glycerin with various fatty
acids. These may be separated by saponifying the fat or oil with sodium
or potassium hydroxide, dissolving the resulting soap in hot water, and
adding sufficient dilute sulphuric acid to decompose the soap, when an
oily layer gradually rises to the surface. This when melted by gentle
heat and washed free from mineral acid, is soluble in alcohol and
reddens blue litmus paper. It consists of the insoluble fatty acids of
the fat, those soluble in water, such as acetic, propionic, butyric,
caproic, caprylic, and capric, remaining for the most part dissolved in
the aqueous portion underneath.

All the acids naturally present in fats and oils are mono-basic,
_i.e._ contain only one carboxyl (COOH) group, but they may be
arranged in five classes or homologous series, based on their chemical
constitution, these series having the following general formulæ:—

I. Stearic Acid Series CₙH₂ₙ₊₁COOH.
II. Oleic Acid Series CₙH₂ₙ₋₁COOH.
III. Linolic Acid Series CₙH₂ₙ₋₃COOH.
IV. Linolenic Acid Series CₙH₂ₙ₋₅COOH.
V. Ricinoleic Acid Series CₙH₂ₙ₋₇COOH.

The more important members of these series, together with their
formulæ, melting-points, and principal occurrence, are given in the
following tables:—

_I. Stearic Series_

The acids of this series are all what is termed saturated compounds,
_i.e._ they do not form addition compounds when brought in contact
with bromine, iodine, or ozone. The two first are liquid at ordinary
temperatures, distil unchanged under atmospheric pressure, and are
miscible with water in all proportions. The next four are more or less
soluble in water, and readily distil with steam, as does also lauric
acid, though the latter is practically insoluble in cold water, and
only dissolves very slightly in boiling water. These first seven acids
are termed _Volatile Fatty Acids_, and on their volatility are based
the Reichert process and its modifications and the Polenske method
for the examination of butter fat for adulteration, vide pp. 111-114.
The higher acids of the group are solid, and are completely insoluble
in water. The whole series is readily soluble in warm alcohol, and
undergoes no change when heated with solid caustic alkali.

_II. Oleic Acid Series_

These acids differ essentially from those of Series I. in being
unsaturated, and combine directly with bromine, iodine, and ozone. The
earlier members are readily reduced, by the action of sodium amalgam in
alkaline solution, to the corresponding acids of Series I. Thus:—

C₄H₇COOH + H₂ = C₄H₉COOH
(Tiglic acid) (Hydrogen) (Valeric acid)

Unfortunately, however, from the candlemaker’s point of view, this
reduction does not take place in the case of the higher acids of the
series, and for the reduction of oleic acid to stearic acid other
methods have to be adopted.

Acids of this group may also be converted into those of the Stearic
Acid Series by heating them to 300° C. with solid potassium hydroxide,
when hydrogen is also liberated, the reaction, with oleic acid, for
example, being generally represented by the equation:—

C₁₈H₃₄O₂ + 2KOH = KC₂H₃O₂ + KC₁₆H₃₁O₂ + H₂

though since, as Edmed has shown, a considerable quantity of oxalic
acid is also formed, the action must strictly be more complex than this
indicates.

One of the most important properties of this group of acids, and one
which is of great value in judging the purity of olive oil, is the
elaidin reaction, which is based on the formation of isomeric acids of
higher melting-point by these acids when treated with nitrous acid.
Oleic acid, for example, when acted upon by nitrous acid, yields
elaidic acid, melting at 45° C., and erucic acid gives brassic acid,
melting at 60° C. A similar reaction also takes place with the neutral
glycerides of these acids, olein being converted into elaidin, which
melts at 32°.

The lead salts of the acids of this series are much more soluble in
ether, and the lithium salts more soluble in alcohol, than those of
the stearic series, upon both of which properties processes have been
based for the separation of the solid from the liquid fatty acids.

_III. Linolic Acid Series_

These acids are also unsaturated, and readily combine with bromine,
iodine, oxygen, or ozone. They do not give an elaidin reaction when
treated with nitrous acid, and their lead salts are soluble in ether.

_IV. Linolenic Acid Series_

These acids are very similar in properties to those of the preceding
series, but combine with six atoms of bromine or iodine, whereas the
latter only combine with four atoms.

_V. Ricinoleic Acid Series_

This acid combines with two atoms of bromine or iodine, and when
treated with nitrous acid is converted into the isomeric ricinelaidic
acid, which melts at 52-53° C. It differs from most fatty acids in
possessing optical activity, its specific rotation being

[_a_] = +6° 25′.
ᵈ

CHAPTER II

RAW MATERIALS USED IN THE MANUFACTURE OF EDIBLE FATS AND OILS

It is unnecessary to emphasise the absolute importance that all
materials used for the preparation of edible fats and oils should be as
fresh, odourless, and free from all impurities as possible. Albuminous
matter, which facilitates the production of rancidity by enzymic
action, must be carefully removed, and freedom from any appreciable
quantity of free fatty acids is most essential. The absence of these
latter should be sufficient to guarantee the absence of any rancidity,
which though not due to, is generally accompanied by their production.

The methods of treatment by which freedom from odour and free fatty
acids is secured, are fully described in the next chapter, and in the
case of some of the materials, their actual preparation is dealt with
in subsequent chapters. The following paragraphs give briefly the
source, origin, and properties of the raw material employed in the
industry.

=Tallow.=—Ordinary “dripping” is simply an impure form of tallow, but
the name tallow is generally used to denote the adipose fat or “suet”
from sheep and oxen, being distinguished in commerce as mutton or beef
tallow. The latter is somewhat softer in consistency, and is therefore
more usually employed in the manufacture of margarine, though mutton
tallow is also occasionally used. “Premier jus” consists of the less
firm constituents of tallow, separated from the harder stearin by
partial melting and pressure, as described in Chapter VI. p. 69.

The chief sources of imported tallow are Australia, New Zealand, and
North and South America. Some of the carefully picked tallow intended
for margarine making is shipped to England “unrendered,” but in some
cases the fat is not only rendered, but also converted into “premier
jus” abroad before shipment. Large quantities of tallow are also
produced in Great Britain, and much of the rough fat is carefully
hand-picked, rendered separately, and the product sold for margarine
making. The following figures have been obtained for some typical
samples of tallow:—

+-----------------+----------------+-----------------+--------+
| | | Free Acidity | |
| Tallows. | Saponification | (as Oleic Acid) | Titre, |
| | Value. | per cent. | °C. |
+-----------------+----------------+-----------------+--------+
| _Mutton_:— | | | |
|Selected English | 197·6 | 1·45 | 47 |
|Australian | 197·4 | 0·48 | 48·3 |
|South American | 197·3 | 1·11 | 47 |
|North American | 197·5 | 1·32 | 44 |
| | | | |
| _Beef_:— | | | |
|Selected English | 197·5 | 2·40 | 44 |
|Australian | 197·5 | 1·68 | 43·9 |
|South American | 197·3 | 0·81 | 45 |
|North American | 197·4 | 1·97 | 41·5 |
+-----------------+----------------+-----------------+--------+

=Lard.=—This fat, obtained from the pig, is an important constituent
of many butter substitutes, especially in the United States, whence
most of that imported into this country is obtained. Its method of
preparation and various qualities are fully described in Chapter V.

=Lard Oil=, obtained by subjecting the softer varieties of lard to
hydraulic pressure at a moderate temperature, is also dealt with in
Chapter V.

=Cocoanut Oil.=—This oil, after special refinement, is extensively
used in margarine and chocolate-cream manufacture, and is also
sold under various fancy names as _vegetable butter_. There are two
principal commercial varieties, Cochin and Ceylon, the former obtained
from Cochin (Malabar) or the Philippine Islands, and the latter from
Ceylon. The following are analyses of typical samples:—

+--- -------+----------------+-------------+--------+------------+
| | | Acidity (as | | Refractive |
| | Saponification | Oleic Acid) | Titre, | Index at |
| | Value. | per cent. | °C. | 25 °C. |
+-----------+----------------+-------------+--------+------------+
|Cochin oil | 255 | 1·5 | 23·5 | 1·4540 |
|Ceylon oil | 258·2 | 5·47 | 23 | 1·4535 |
+-----------+----------------+-------------+--------+------------+

=Maize Oil=, expressed from maize, and obtained chiefly from the United
States, is occasionally used as an edible oil. A sample of refined
maize oil has given the following figures on analysis:—

+---------+--------------+------+-----------+--------+----------+
| Specific| | |Acidity (as| |Refractive|
| Gravity |Saponification|Iodine|Oleic Acid)| Titre, | Index at |
|at 15° C.| Value. |Value.| per cent. | °C. | 20° C. |
+---------+--------------+------+-----------+--------+----------+
| 0·9243 | 192 | 123 | 0·40 | 17·2 | 1·4766 |
+---------+--------------+------+-----------+--------+----------+

=Cotton-Seed Oil.=—This is obtained by expression from the seeds of the
various kinds of cotton tree, grown extensively in America, Egypt, and
India. A considerable quantity of the oil is expressed from the seed in
this country, principally at Hull. The refined oil is used in making
artificial butter, and also for culinary purposes. The best cotton-seed
oil, used for margarine manufacture, is sold under the name of “butter
oil.” The following are typical figures for a refined cotton-seed oil:—

+---------+--------------+------+-----------+------+----------+
| Specific| | |Acidity (as| |Refractive|
| Gravity |Saponification|Iodine|Oleic Acid)|Titre,| Index at |
|at 15° C.| Value. |Value.| per cent. | °C. | 20° C. |
+---------+--------------+------+-----------+------+----------+
| 0·9229 | 193 | 115 | 0·24 | 33·6 | 1·4721 |
+---------+--------------+------+-----------+------+----------+

=Cotton-Seed Stearin.=—This is the solid residue remaining when the
deposit obtained from ordinary refined cotton-seed oil by chilling is
pressed. Its consistency is very similar to that of butter, and it
is used in the preparation of some artificial butters. Its average
properties are as follows:—

+----------------+--------+-----------------+--------+
| | | Acidity | |
| Saponification | Iodine | (as Oleic Acid) | Titre, |
| Value. | Value. | per cent. | °C. |
+----------------+--------+-----------------+--------+
| 195 | 93 | 0·05 | 38 |
+----------------+--------+-----------------+--------+

=Olive Oil.=—Edible olive oil is obtained by expression from the fruit
of the olive tree, and is largely used as salad oil, in cookery, and
for tinning sardines. Olive trees are grown extensively in nearly
all the countries bordering on the Mediterranean Sea, also to a
considerable extent in California. The oil obtained from their fruit
varies a good deal in quality, according to its source, oils from
Leghorn or Gallipoli being the most esteemed. The following figures
were given by a typical high-class oil:—

+----------------+--------+-----------------+--------+------------+
| | | Acidity | | Refractive |
| Saponification | Iodine | (as Oleic Acid) | Titre, | Index at |
| Value. | Value. | per cent. | °C. | 20° C. |
+----------------+--------+-----------------+--------+------------+
| 190 | 89 | 1·8 | 21 | 1·4704 |
+----------------+--------+-----------------+--------+------------+

=Arachis Oil (Earth-Nut or Pea-Nut Oil).=—This oil, used occasionally
in margarine to reduce its firmness, and a useful table oil, is
obtained from the nuts of _Arachis hypogæa_, a herb cultivated largely
in North America, India, and Western Africa. Most of the oil is
expressed in Southern France, and its chief use appears to be as an
adulterant or substitute for olive oil, which it closely resembles in
many respects. The following figures were given by a sample of the
refined oil:—

+---------+--------------+-------+-----------+------+----------+
| Specific| | |Acidity (as| |Refractive|
| Gravity |Saponification| Iodine|Oleic Acid)|Titre,| Index at |
|at 15° C.| Value. | Value.| per cent. | °C. | 20° C. |
+---------+--------------+-------+-----------+------+----------+
| 0·9205 | 193 | 87 | 0·22 | 24 | 1·4712 |
+---------+--------------+-------+-----------+------+----------+

=Sesame Oil.=—This oil is frequently employed in margarine manufacture,
its use to the extent of 10 per cent. being compulsory in Germany and
other countries, in order to simplify the detection of adulteration of
butter with butter substitutes. It is largely expressed in Southern
France from the seeds of the sesame plant, which is grown in the
Levant, India, Japan, and West Africa. A representative sample gave the
following results:—

+---------+--------------+------+-----------+------+----------+
| Specific| | |Acidity (as| |Refractive|
| Gravity |Saponification|Iodine|Oleic Acid)|Titre,| Index at |
|at 15° C.| Value. |Value.| per cent. | °C. | 20° C. |
+---------+--------------+------+-----------+------+----------+
| 0·9227 | 190 | 110 | 1·84 | 22·8 | 1·4731 |
+---------+--------------+------+-----------+------+----------+

=Palm-Nut Oil (Palm-Kernel Oil).=—This oil is obtained by expression
or extraction in Europe from the kernels of the palm-tree fruit
imported from Africa. It very closely resembles cocoanut oil in
character and is used for similar purposes. The following results were
obtained with normal samples of English and Hamburg oils respectively:—

+----------------+-----------------+--------+------------+
| | Acidity | | Refractive |
| Saponification | (as Oleic Acid) | Titre, | Index at |
| Value. | per cent. | °C. | 20° C. |
+----------------+-----------------+--------+------------+
| 245 | 4·4 | 24 | 1·4553 |
| 243 | 7·7 | 23·8 | 1·4553 |
+----------------+-----------------+--------+------------+

=Sunflower-Seed Oil= is expressed from sunflower seeds, the principal
source of which is Southern Russia and Caucasia. It is also intended to
cultivate them in South Africa, recent experiments having been found
satisfactory. The following figures were obtained with a typical sample
of the oil:—

+----------+----------------+--------+-----------------+--------+
| Specific | | | Acidity | |
| Gravity | Saponification | Iodine | (as Oleic Acid) | Titre, |
|at 15 °C. | Value. | Value. | per cent. | °C. |
+----------+----------------+--------+-----------------+--------+
| 0·9259 | 191 | 126·2 | 0·81 | 17 |
+----------+----------------+--------+-----------------+--------+

=Cacao Butter=, =or Oil of Theobroma=, is expressed from the beans of
Theobroma Cacao, which is grown in Central America, and is the source
of ordinary cocoa. It is used in pharmacy, but is principally employed
in the manufacture of chocolate cream (vide Chapter VII. p. 84), the
supply of which is very much inferior to the demand. It is a yellowish
white, brittle solid, at the ordinary temperature, bleaching with age,
and the following figures are typical of those given by an average
sample:—

+----------------+-----------------+--------+--------+
| | Acidity | | |
| Saponification | (as Oleic Acid) | Titre, | Iodine |
| Value. | per cent. | °C. | Value. |
+----------------+-----------------+--------+--------+
| 193 | 1·1 | 47·9 | 33·6 |
+----------------+-----------------+--------+--------+

=Palm Oil.=—This is obtained from the fruit of the palm trees grown
extensively along the West Coast of Africa. There are many qualities,
that from Lagos being the best. The oil is occasionally employed in
the manufacture of margarine, to which it imparts a yellow colour. Its
use was recently the subject of an action in the United States Supreme
Court, the decision of which was that palm oil must be regarded as an
artificial colouring matter, and must pay duty as such, even if used as
a material ingredient to improve the wholesomeness and flavour of the
product.

=Soya Bean Oil=, expressed in China from the Soya bean, is now coming
extensively into use, and is already employed for culinary purposes. It
has, according to De Negri and Fabris, the following properties:—

+-----------------+----------------+--------+
|Specific Gravity | Saponification | Iodine |
| at 15° C. | Value. | Value. |
+-----------------+----------------+--------+
| 0·9242 | 191 | 121·3 |
+-----------------+----------------+--------+

The three following are among the more recently discovered oils, and
are now sometimes used in the preparation of vegetable butter:—

=Shea Butter.=—This is extracted from the kernels of the Bassia Parkii,
grown in Africa and Eastern India. It is somewhat tough and sticky, and
has the following properties:—

+---------------+-----------------+--------+------------+
| | Acidity | | Refractive |
|Saponification | (as Oleic Acid) | Titre, | Index at |
| Value. | per cent. | °C. | 60° C. |
+---------------+-----------------+--------+------------+
| 181 | 8·2 | 53·2 | 1·4566 |
+---------------+-----------------+--------+------------+

=Mowrah-Seed Oil.=—This oil, obtained from the seeds of Bassia
longifolia and Bassia latifolia, is largely imported into this country
from India. It gives the following figures on analysis:—

+---------------+-----------------+--------+------------+
| | Acidity | | Refractive |
|Saponification | (as Oleic Acid) | Titre, | Index at |
| Value. | per cent. | °C. | 60° C. |
+---------------+-----------------+--------+------------+
| 187 | 10 | 43·4 | 1·4518 |
+---------------+-----------------+--------+------------+

=Margosa Oil.=—This is prepared from the seeds of _Melia azedarach_, a
tree found in most parts of India and Burmah. According to Lewkowitsch
(_Analyst_, 1903, pp. 342-344) it has the following analytical
characteristics:—

+----------------+--------+--------+
| Saponification | Iodine | Titre, |
| Value. | Value. | °C. |
+----------------+--------+--------+
| 196 | 69·6 | 42 |
+----------------+--------+--------+

Of the other raw materials mention may be made of milk, which should
not contain less than 3 per cent. fat, and may be fresh or “soured”;
water, which should be as pure as that of a drinking supply; salt
(sodium chloride), which is readily obtainable in a very pure state;
and colouring matter, which generally consists of annatto.

CHAPTER III

REFINING, BLEACHING, AND DEODORISING FATS AND OILS

Physical Methods—Washing, freezing, filtration,
treatment with charcoal and fuller’s earth,
steaming. Chemical methods—Caustic soda, sodium
carbonate and silicate, alkaline earths, ozone,
hydrosulphites, sodium bisulphite, organic
peroxides.

Although, as was pointed out in Chapter II., too much stress cannot be
laid upon the importance of using only the freshest materials of the
best possible quality in the manufacture of edible fats, yet even these
frequently require a certain amount of preliminary treatment in order
to bleach, deodorise, or refine them and render them palatable for
human food. Numerous processes, both physical and chemical, have been
devised, and in many cases patented, for these different purposes, and
the following is a summary of the more important ones.

=Physical Methods.=—Among the physical methods employed may be
mentioned washing with hot water, the removal of suspended matter by
settling or filtration, and of excess of stearin by subjection to
low temperatures, bleaching by filtration through animal charcoal
or fuller’s earth, and deodorising by injecting steam either at
atmospheric pressure, in vacuo, or in presence of an indifferent gas.

The impurities in freshly expressed oil which are partly in suspension
and partly in solution, consist chiefly of dirt, fragments of vegetable
fibre, and mucilaginous and albuminous substances. A portion of them
rapidly deposits when the oil is allowed to stand, and the upper liquid
may then be drawn off from the sediment and subjected to filtration or
to further refining processes.

In some cases a simple filtration, after standing for a short time,
is sufficient to render the oil brilliant, but special treatment is
necessary when a large proportion of albuminous matter is present,
since such oils either pass through the filter without becoming bright,
or if a closer filtering medium is used, the pores of the filter
speedily become clogged.

Various methods are employed to coagulate or precipitate albuminous
matters before filtration, such as dry heat, or the introduction of
fine jets of steam, or the addition of a small quantity of insoluble
powder (_e.g._ fuller’s earth or kieselguhr), which as it subsides
attracts and carries down simultaneously the particles of the gum-like
mucilage.

The formation of an insoluble precipitate within the oil answers the
same purpose. Thus, in Linde’s process a small quantity of milk is
introduced and the mixture heated so as to coagulate the casein, the
subsidence of which removes at the same time the substances that cause
turbidity in the oil.

Other substances, such as solutions of tannin, are used in the same way
in refining oils for technical purposes, but are inadmissible in the
case of edible oils.

In the removal of dissolved impurities, alkali solutions, milk of lime,
or magnesia are reagents in common use, while dilute sulphuric acid is
employed to clarify linseed and certain fish oils for industrial uses.

To facilitate the purification of oils by washing with water, Dubovitz
has recently recommended the addition to the water of aluminium
sulphate, in the proportion of about ¾ oz. to 220 gallons per degree
of hardness. This forms with the lime in the water a bulky, colloidal
precipitate, which serves to bleach and clarify the oil.

=Removal of Stearin.=—When certain oils are exposed to a low
temperature they become turbid and in some cases give a white deposit.
This consists of glycerides of the more solid fatty acids, and is
known as “stearin,” and its formation is frequently regarded as
objectionable, notwithstanding the fact that when the oil is gently
heated the stearin is redissolved.

In the preparation of the best edible oils, therefore, a process of
chilling followed by filtration is often employed in order to remove
part of the stearin, and the oils thus treated may then be exposed to a
low temperature without giving a further deposit.

Oils treated in this way are commonly known as “winter oils,” and those
which will only keep brilliant at the ordinary summer temperature are
termed “summer oils.”

The solid fat separated in this way from cotton-seed oil is known as
cotton oil stearin, although it is quite free from stearic acid. A
similar process is employed for the separation of cocoanut and palm-nut
oils into their respective stearins and oleins (see _Chocolate Fats_).

=Methods of Filtration.=—The types of filter press used in the
filtration of oils are very varied. A common form consists of a
hydraulic press containing a series of communicating plates with rims
raised so as to form a space into which filter cloths may be fitted.

In other forms of apparatus the oil is introduced from below into
a chamber, and rises upwards through the filtering medium into a
compartment in which a partial vacuum has been created. Or methods
of centrifugal filtration may be employed, as in apparatus in which
the oil is introduced into a revolving chamber with a perforated wall
round which is wrapped a filtering cloth. The oil is flung against the
wall of the revolving chamber in a fine state of division, and passes
through the filtering medium into an outer chamber, whence it can be
drawn off.

The materials used as filtering media include sand, kieselguhr, Spanish
clay, fuller’s earth, animal charcoal, paper pulp, and a mixture of
wool and vegetable fibres disintegrated into a pulp.

=Chemical Methods.=—The number of chemicals employed in refining oils
and fats for edible purposes is necessarily very limited. It is of
course very objectionable to employ any reagent which is poisonous,
though the use of barium oxide has been patented by Rocca (Fr. Pat.
325,381, 1902), and processes involving the use of mineral acids
are, in general, inadmissible, as they spoil the flavour of the oil.
The chief reagents employed are caustic soda (sodium hydroxide),
sodium carbonate, sodium silicate, calcium or magnesium oxide, ozone,
hydrosulphites, formaldehyde-sulphoxylates, and organic peroxides.

_Caustic Soda._—Of the alkaline refining process the treatment of
cotton-seed oil with a solution of sodium hydroxide or potassium
hydroxide is the best example. The oil is mechanically agitated with
the alkali solution, which usually has a specific gravity of about
1·10, either with or without the aid of heat, and the mixture then
allowed to stand until it separates into two layers, the lower of which
contains a sediment of impurities. This is drawn off, and the treatment
repeated, but this time with a more dilute solution of alkali, and
finally the oil thus clarified is washed with water to remove the
excess of alkali.

In this process of refining not only are the albuminous and resinous
matters precipitated, but the free fatty acids in the oil are
neutralised, and accordingly freshly prepared cotton-seed oil is almost
neutral in its reaction, and has a bland taste. The treatment also
removes a large proportion of the colouring matter separated from the
seed in the expression of the oil, and changes the dark-brown colour of
the crude product to a light-golden tint.

The residue left from the refining of cotton-seed and other oils is
a thick deposit containing the impurities in a concentrated form,
together with a considerable proportion of oil; such residues are known
as “foots,” and are utilised in the manufacture of soap.

The amount of caustic soda required depends on the degree of acidity
of the oil, which it should be just sufficient to neutralise. The
acidity of the oil is therefore first determined, as described in
Chapter VIII., and the quantity of caustic soda calculated which will
neutralise the given bulk of oil to be treated. The following is a more
detailed account of the process:—

The calculated quantity of alkali is dissolved in water, the solution
diluted to 12 or 15° Tw. (8° or 10° B.), and one-third of it added,
either in a fine stream, or through a sprinkler, to the oil contained
in a steam-jacketed tank. The mixture is now heated first to 100°
F., and then gradually to 120° F., the whole being well agitated
mechanically, or by blowing a current of air through a pipe inserted to
the bottom of the tank.

After about fifteen minutes the agitation is stopped, and the oil
allowed to rest for some time, preferably overnight, to allow the soap
and impurities to settle down to the bottom, whence they may be drawn
off. This treatment is then repeated a second and third time, with the
same quantity of caustic soda solution, but usually of weaker strength,
and in exactly the same manner as just described, after which a clear,
yellow oil should be obtained.

The agitation with air must not be unduly prolonged, as this tends to
oxidise the oil, raising its specific gravity and refractive index, and
also injuring its flavour.

Treatment with caustic soda solution is also frequently employed for
refining other vegetable oils, notably cocoanut oil. In all cases
the principle is the same, viz., combination of the alkali with the
free fatty acids to form soap, which on settling carries down with it
colouring matter and other impurities. Only a weak solution, of say 12°
Tw. (8° B.), should be used, and the quantity added should not be more
than sufficient to neutralise the free acid, since otherwise some of
the neutral oil may be saponified.

_Sodium Carbonate._—This may be employed instead of caustic soda to
neutralise the free fatty acids of an oil or fat. In practice, however,
it is less frequently used by itself for refining purposes, though
there is less risk of saponification of the neutral oil if a slight
excess is added with this reagent than with caustic soda.

A process has been patented in France by G. Muller (Fr. Pat. 334,366,
1903) for the treatment of cacao butter with sodium bicarbonate. The
fat is heated with sodium bicarbonate and water, then cooled with
constant agitation until it congeals, allowed to stand for twenty-four
hours, and finally subjected to a process of pressing and kneading. The
fat thus treated is claimed to be softer and less brittle.

_Sodium Silicate._—This is an alkaline salt, and its action is very
similar to that of sodium carbonate. Its use for bleaching oils
and fats has been patented by Godard (Eng. Pat. 22,085, 1903), who
mixes the oil with sodium silicate, separates the soap formed, and
then deodorises the neutral oil by means of steam in a fine state of
division.

_Alkaline Earths._—Lime and magnesia are sometimes used for removing
the free fatty acids from oils and fats, insoluble calcium and
magnesium soaps being formed. In Rocca’s patent, to which reference has
already been made (vide _supra_), the oil is first neutralised with
caustic soda or sodium carbonate, decanted from the resulting soap, a
small quantity of strong acid added to decompose any soap remaining,
and the oil finally neutralised with lime, magnesia, or baryta.

Fresenius (Eng. Pat. 19,171, 1902) neutralises the oil with caustic
soda, lime, or magnesia, under a pressure of 2 or 3 atmospheres, either
in the presence of carbon to prevent oxidation, or according to a later
process in an atmosphere of an inert gas. The increased pressure is
claimed to facilitate the separation of the soap emulsion.

=Bleaching of Oils.=—The colouring matter of crude oils consists of
chlorophyll, which gives them a greenish tinge, or of substances
frequently of a resinous nature, which impart a brown colour.

In the case of some oils, such as olive oil, the natural greenish tint
is allowed to remain, but the dark colour of certain other crude oils
has to be reduced before the product is saleable.

As was mentioned above, treatment with alkali removes from cotton-seed
oil a large proportion of the dark colouring matter at the same time as
the constituents that cause turbidity.

The methods in which fuller’s earth or milk is used to refine oils
have also some effect in producing a filtrate of lighter colour, while
a treatment with freshly prepared animal charcoal is effective as a
decolorising process in some cases.

_Charcoal._—Bleaching with charcoal may be effected by mixing the oil
with 1 to 5 per cent. of _animal_ charcoal, in a granular form, warming
for a short time, and filtering through a filter press. The bleaching
action of animal charcoal, attributed by Knecht to the presence of
nitrogen compounds, is greater in the presence of acid.

Crude charcoal requires preliminary treatment before use for bleaching
purposes. It should be well boiled, first with pure water, and then
after the addition of sufficient sodium carbonate or hydroxide to
render it alkaline. It is next washed free from alkali, and boiled for
twelve hours with four times its weight of a mixture of equal parts
of commercial hydrochloric acid and water, after which it is washed
free from acid, dried, and burned in closed vessels. A good bleaching
charcoal is thus obtained.

_Fuller’s Earth._—Fuller’s earth (aluminium magnesium hydrosilicate)
should be dehydrated by roasting prior to use, in order to secure the
best results. The quantity required varies from 2-5 per cent. for
cocoanut, palm-kernel, and olive oils, to upwards of 10 per cent. for
arachis and cotton-seed oils, and the oil should be thoroughly mixed
with the reagent and maintained at a temperature of say 100° F. for
about fifteen minutes, and then filtered through a filter press. The
fuller’s earth retains about 80 per cent. of the oil, which may be
extracted by means of a solvent, the latter distilled off, and the
recovered oil treated with a fresh quantity of fuller’s earth. The
spent fuller’s earth may be “regenerated” by heating it up to 400-500°.
Fuller’s earth is frequently used in America for the filtration of
“premier jus.”

According to Hirzel (_Chem. Rev. Fett- u. Harz-Ind._, 1904, 116-118;
145-146), the earthy flavour sometimes remaining after contact with
fuller’s earth may be removed by washing with 10 per cent. of a 10 per
cent. solution of brine, and by adding 1 to 1½ per cent. of powdered,
dry sodium bicarbonate.

Godard (Eng. Pat. 22,086, 1903) carries out the agitation with reagents
_in vacuo_ in order to prevent oxidation of the oil.

No very definite details as to the quantity of charcoal or fuller’s
earth to be used, the temperature to which the oil should be raised in
contact with them, and the time it should be maintained thereat, can be
given, as these vary considerably for different oils, and can only be
determined by actual experiments with the particular oil it is required
to bleach.

The use of finely divided alumina, bauxite, or magnesite previously
ignited at a low temperature, has also been patented for decolorising
oils, and a process for the recovery of spent decolorising materials
(which consists in mixing them with salt water, heating the mixture
to about 85° C. with sulphuric acid, then treating it with sodium
carbonate and mechanically agitating it for a short time) has been
patented by the Soc. Anon. Huilerie et Savonnerie de Lurian (Fr. Pat.
499,915, 1909). The carbon dioxide liberated by this treatment carries
the oil to the surface.

Methods in which chlorine or bleaching powder are employed are only
applicable for bleaching oils intended for the making of soap or other
technical purposes, owing to the reagent attacking the glycerides and
imparting a flavour. For similar reasons Watts’ bichromate process of
bleaching palm oil is also unsuitable for the treatment of fat intended
for food.

Methods of oxidation, either by means of hot air passed through
the heated oil or fat, or by means of ozone or ozonised air, under
controlled conditions, are employed both to obtain paler oils and to
remove substances of unpleasant odour.

The bleaching of beeswax by exposing it in thin strips to the action
of air and sunlight has long been practised, and Japan wax is also
rendered nearly white by similar means.

The use of artificial light in place of sunlight is claimed in several
patents for bleaching oils, such as cotton-seed oil. The oil is made
to pass across a transparent surface through which are transmitted the
rays from a powerful arc light.

Ultra-violet rays, such as those emitted by the mercury vapour lamp,
are employed as the bleaching agent in similar processes.

_Ozone._—The use of ozone as a bleaching agent has long been known, but
its application to the treatment of oils and fats has hitherto met with
little success. It has been the subject of many patents, among which
may be mentioned that of Andreoli (Eng. Pat. 14,570, 1898), who makes
use of the joint action of ozone and a hypochlorite solution, and that
of J. Harris (Eng. Pat. 22,430, 1906). Harris first ozonises the oil at
a temperature of 100° to 180° F. for fifteen to thirty minutes, until
there is an appreciable rise—say 0·5 per cent.—in the free fatty acids.
The treatment with ozone is then stopped, and the oil neutralised with
alkali, preferably an aqueous solution of caustic soda at about 15° Tw.
(10° B.). The impurities are next separated, and the oil dried by means
of a current of air while warm, after which it may be still further
refined by heating it with 5 per cent. of aluminous earth, followed by
filtration.

This latter process seems to be rather a mistaken one, as from
experiments made by one of the authors (S.), the best results are
obtained when the ozonisation is only carried to such a point that
there is no appreciable increase in the free acidity of the oil.

Recent experiments by him on the bleaching and deodorising action of
pure ozone _free from nitrogenous compounds_, as obtained with the
Ozonair apparatus, have given results which are most promising. Palm
oil, even of the crudest description, has been most effectively and
cheaply bleached by merely passing a strong current of ozonised air
through it, and the colour of certain other vegetable oils has been
distinctly improved by this treatment; while in the case of a very acid
sample of cocoanut oil, the fat was not only made whiter in colour, but
had also almost entirely lost its characteristic odour. Hence there
seems to be a likelihood of the successful employment of the ozone
process for this purpose in the future.

_Hydrosulphites_ or “hyposulphites.”—Sodium hydrosulphite, obtained
by digesting a concentrated solution of sodium bisulphite with zinc
dust or turnings, is a powerful reducing agent, and has been patented
as a means of bleaching oils and fats by Metz and Clarkson (Eng. Pat.
11,983, 1906). It is particularly applicable to maize oil, which may
be bleached by agitating 200 parts of the oil with 600 parts of water
and 15 parts of sodium hydrosulphite for ten hours in a closed vessel,
allowing the mixture to stand for thirty-two hours, and then separating
the oily layer.

Sodium hydrosulphite formaldehyde, which was shown by Baumann, Thesmar,
and Frossard in 1904 to be commercially a mixture in almost equal
proportions of sodium sulphoxylate formaldehyde and sodium bisulphite
formaldehyde, is also recommended for the purpose, the oil being heated
to 70° C. with this reagent in a closed vessel, and then allowed to
stand.

The formaldehyde-sulphoxylates are now sold under a variety of fancy
names, the sodium compound being termed _Rongalite C._ and _Hydraldite
C._, and the zinc salt _Decroline_.

_Sodium Bisulphite._—This salt, which possesses the property of
combining with aldehydes, has been utilised in some cases for
deodorising oils and fats, with good results.

_Organic Peroxides._—The Vereingte Chem. Werke have recently patented
the use of various organic peroxides (such as those of benzoyl, acetyl,
and acetone, together with the oxidation products obtained by the
action of nitrogen tetroxide on organic compounds) for the bleaching of
oils and fats. The oil is heated to 100° C. with about 0·2 per cent. of
the peroxide, and allowed to stand in a warm place for a short time,
until bleaching has taken place.

There is now a large number of per-salts available, _e.g._,
persulphates, percarbonates, perborates, which are being utilised for
various bleaching purposes, but so far they do not appear to have been
employed to any appreciable extent in the treatment of oils and fats,
though ammonium persulphate (palidol) is now being used for bleaching
soap in the pan.

=Deodorisation of Fats.=—The odours of oils and fats are due to the
presence of small quantities of volatile substances, either derived
from the vegetable substance as in the case of maize and wheat oils, or
formed by slight decomposition of the oil itself.

It is chiefly in connection with cocoanut oil, which forms the basis of
so many vegetable lards and butters, that the problem of deodorisation
of a fresh fat has to be faced.

According to the recent research of Haller and Lassieur (_Comptes
Rend._, 1910, 150, 1013), the unpleasant odour of commercial cocoanut
oil must be attributed, partly to a process of decomposition of the
glycerides, with the liberation of fatty acids (caproic, caprylic,
capric acids, etc.) with a pronounced odour; and partly to the
presence of certain substances, which include methyl-heptyl ketone
and methyl-nonyl ketone. Traces of these may also be detected in the
refined fat, and account for its odour when heated. The substances
to which the odour is due may be obtained in the form of an essence
(échappés) by distilling the cocoanut oil in a current of superheated
steam.

Speaking broadly, two methods only have so far been discovered, or,
at any rate, published, for the deodorisation of cocoanut oil—(1)
washing out of the odoriferous bodies with alcohol, and (2) their
volatilisation by treatment with steam. Other unpublished processes
are doubtless used by some manufacturers, but their secrecy is very
jealously guarded.

The washing of cocoanut oil with alcohol of course removes free fatty
acids, which are soluble therein. This method of treatment was first
introduced by Chevreul, and has been also utilised by Schlinck, who
employed a joint process of washing with alcohol and treatment with
charcoal. A special apparatus for its application was patented by
Urbain and Feige (Fr. Pat. 361,966, 1905), consisting of a series of
vessels so arranged that the oil descends from vessel to vessel, and
meets hot alcohol circulating in the opposite direction, so that the
more impure oil comes in contact with the more impure alcohol. The
temperature is maintained at 70° C. during the treatment, and means are
provided for evaporating and condensing the alcohol after extraction is
complete.

An improvement upon this patent has been since protected by the
patentees, in which sufficient alkali is added to combine with the free
fatty acids prior to the extraction with alcohol.

With so volatile a substance as alcohol, there is necessarily a
considerable loss by evaporation during working, and the cost of
alcohol in this country is too high for the process to be economical.

The treatment of cocoanut oil with steam in order to deodorise it dates
back to 1882, when a process was patented in Germany by Jeserich and
Meinert, in which the volatile fatty acids were first driven off by
passing high pressure steam at 6 to 8 atmospheres into the fluid oil,
with constant stirring for about two or three hours, after which steam
was shut off, and the non-volatile fatty acids separated by addition of
0·25 per cent. of calcined magnesia, the magnesium soap formed rising
to the surface, whence it could be skimmed off.

Several modifications of this process have since been patented.
Klimont (Eng. Pat. 3164, 1902) neutralises the oil with alkali prior
to treatment with superheated steam, and then removes non-volatile
impurities by either raising the temperature of the oil to above 100°
C., treating it with calcium or magnesium hydroxide, or extracting
it with some solvent such as acetone, which dissolves the oil and
precipitates the impurities.

The Fabrique de Prod. Chim. de Thann et de Mulhouse treat the oil with
steam in the absence of air, either _in vacuo_, or in an atmosphere of
an indifferent gas.

In another method of deodorisation cocoanut oil is freed from its
more fluid constituents (as in the preparation of chocolate fats,
_q.v._) and the fatty acids eliminated in the form of calcium salts by
treatment with lime; sodium silicate is employed in another process
as the means of removing the fatty acids. Yet however carefully the
odoriferous substances may have been removed, the readiness with which
cocoanut oil undergoes hydrolysis, and the nature of the fatty acids
contained in its glycerides, renders this fat particularly liable to
acquire an odour again, after having been exposed for a short time to
the air.

=Treatment of Rancid Fats.=—Although the practice is to be condemned,
it is not uncommon for fats that have become slightly rancid to be
subjected to treatment to eliminate the compounds to which rancidity is
due, and thus enable the fat to be blended with fresh fats.

In the development of the changes understood by the term “rancidity,”
the glycerides undergo hydrolysis with the liberation of fatty acids,
which are in turn decomposed or oxidised, with the formation of various
compounds such as fatty anhydrides, aldehydes, and hydroxy acids.

These changes are brought about under the influence of light and
atmospheric oxidation, and are probably promoted by enzymic action or
by the influence of micro-organisms when albuminous substances have
been left in the fat.

The removal of free fatty acids is frequently sufficient to make the
oil appear fresh. This may be effected by mechanically agitating
the fat with a suitable proportion of milk of lime or magnesia,
which combine with the free fatty acids to form insoluble calcium or
magnesium soap, which can readily be separated by filtration.

Neutralisation with caustic alkali (as in the refining of cotton-seed
oil) or with a solution of sodium silicate, also effects the removal
of free fatty acids, but the latter reagent is liable to produce an
obstinate emulsion when employed on a large scale.

In another process the rancid oil is treated with a suitable proportion
of precipitated chalk, and is subsequently filtered while hot through a
layer of animal charcoal.

Reference has already been made to the method of dissolving out the
free fatty acids by means of alcohol. Oils in which a process of
hydrolysis has once started are liable, after removal of the free fatty
acids, not to keep so well as freshly expressed products.

Rancidity may be present in an oil without the liberation of free fatty
acids, though, as a rule, the acid value of a fat will afford some
index of the degree of rancidity, since the development of acidity and
of rancidity are often simultaneous.

For the removal of the aldehydic compounds formed in the changes that
occur, a treatment with a strong solution of sodium bisulphite is used
in a process described by Nagel, while volatile products are expelled
by heating the oil in a current of steam at gradually increasing
temperatures.

Other reagents used for sweetening rancid oils are a solution of
ordinary salt, dilute (1 per cent.) sulphuric acid, a solution of myrrh
in methyl alcohol, etc.

As a rule, the different processes are employed successively, and
followed by filtration and drying of the oil.

The tendency of an oil to become rancid depends largely upon the
proportion of volatile fatty acids and unsaturated fatty acids it
contains. Thus butter and cocoanut oil readily turn rancid, whereas
beef stearin and cacao butter will keep for a long time unaltered.

Any oil or fat is best protected from rancidity by keeping it in the
dark in a vessel from which all air is excluded. Rancidity will take
place in the dark, but much less rapidly than when the fat is exposed
to light. This is due to the accelerating effect of light upon the
action of oxygen. Heat has also a pronounced influence in promoting
chemical changes in oils, and cold has a retarding influence, although
it does not stop the oxidation.

The odour of rancid fats that do not (like cocoanut oil) contain
volatile fatty acids is due to the formation of aldehydes or of esters,
the latter being probably produced, in some cases at all events, by the
action of certain micro-organisms upon the liberated glycerin.

Rancidity is accompanied by a decrease in the iodine value of the fat,
which is due to the absorption of oxygen by the unsaturated bonds of
the liquid fatty acids. A determination of this value may therefore, in
some cases, give indications of the freshness of a fat.

A more promising method, however, is to distil the fat in a current of
steam, and to estimate the amount of aldehydes in the distillate.

CHAPTER IV

BUTTER

=Butter Fat.=—The fat contained in suspension in the milk of mammals
differs considerably in chemical composition from the body fat of the
same animals. The latter consists mainly of glycerides of the higher
fatty acids, notably stearic, palmitic, and oleic acids in varying
proportions, whereas in the case of milk fats there is in addition to
compounds of these fatty acids a large proportion of glycerides of
volatile fatty acids.

It is upon this characteristic feature of butter fat that many of the
methods of detecting foreign fats in butter are based.

A specimen of butter fat examined by Brown yielded 86·40 per cent. of
insoluble fatty acids and 8·35 per cent. of soluble volatile fatty
acids. The former included 32·85 per cent. of oleic acid, 1·83 per
cent. of stearic acid, 38·61 per cent. of palmitic acid, 9·89 per
cent. of myristic acid, and 2·57 per cent. of lauric acid. The soluble
volatile acids were made up of 5·45 per cent. of butyric acid, 2·09 per
cent. of caproic acid, 0·49 per cent. of caprylic acid, and 0·32 per
cent. of capric acid.

The low proportion of stearic acid found was in accordance with the
direct estimations made by Hehner and Mitchell, who obtained only small
amounts in their examination of the fatty acids from a large number of
samples of butter fat of different origin. It was interesting to note,
however, that after the fatty acids had been exposed to the air for
some weeks, there was apparently a gradual formation of stearic acid.

The general composition of butter fat, as shown by the examination of
Brown (_supra_), is as follows:—

+----------------------+-----------+
| Glycerides of— | Per Cent. |
+----------------------+-----------+
|Dihydroxystearic acid | 1·04 |
|Oleic acid | 3·95 |
|Stearic ” | 1·91 |
|Palmitic ” | 40·51 |
|Myristic ” | 10·44 |
|Lauric ” | 2·73 |
|Capric ” | 0·34 |
|Caprylic ” | 0·53 |
|Caproic ” | 2·32 |
|Butyric ” | 6·23 |
+----------------------+-----------+

Naturally, different specimens of butter may show wide variations in
the proportions of their different constituents, but the above may be
taken as typical and as an illustration of the more complex character
of milk fat than that of a body fat.

The glycerides in butter fat are probably present in the form of mixed
glycerides, though, as yet, certain proof of this is wanting.

=Butter.=—Commercial butter consists of butter fat, water, casein, and
salt, the proportion of fat usually ranging from about 84 to 87 per
cent.

The following results obtained by Vieth (_Analyst_, 1891, xvi. 1) show
the average composition to be expected:—

+---------------------------+---------+---------+---------+---------+
| | Fat, | Curd, | Salt, | Water, |
| Butter. |per cent.|per cent.|per cent.|per cent.|
+---------------------------+---------+---------+---------+---------+
|Danish (17 samples) | 83·41 | 1·30 | 1·87 | 13·42 |
|English (72 samples) | 86·85 | 0·59 | 1·02 | 11·54 |
|French (fresh, 108 samples)| 84·77 | 1·38 | 0·09 | 13·76 |
| ” (salted, 5 samples) | 84·34 | 1·60 | 2·01 | 12·05 |
|Kiel (4 samples) | 85·24 | 1·17 | 1·35 | 12·24 |
|Swedish (25 samples) | 83·89 | 1·33 | 2·03 | 13·75 |
+---------------------------+---------+---------+---------+---------+

_Water._—Statutory regulations are in force in many countries to limit
the permissible amount of water in butter. In Great Britain and Ireland
pure butter must not contain more than 16 per cent. of moisture, while
the so-called “milk-blended butter” is not allowed to exceed the limit
of 24 per cent.

The following limits are in force in other countries: _Belgium_, 18 per
cent. unless declared; _Germany_, 18 per cent. for unsalted butter and
16 per cent. for salted butter; _United States_, 16 percent.; _Canada_,
16 percent.; _Queensland_, 16 per cent.; _Victoria_, 15 per cent.

These regulations have been found necessary, owing to the readiness
with which a large excess of water (over 25 per cent.) may be churned
into a butter without making it appear abnormally moist or interfering
with its sale.

The effect of “salting” butter is to reduce the amount of moisture, as
is shown in the results of Vieth, quoted in the table given above.

Richmond considers that the best proportion for a butter that is meant
to keep well is 13·5 per cent.

_Salt._—There is no regulation as to the amount of salt that may be
added to butter, and the proportion will depend upon the popular taste;
sometimes as much as 10 per cent. may be found.

_Curd._—This term represents not only the solid nitrogenous substances
derived from the casein of the milk, but also the milk sugar, etc., and
its amount is roughly estimated by subtracting from 100 the percentages
of butter fat, moisture, and ash which have been separately determined.
The proportion thus found varies from a fraction of 1 per cent. to
about 1·75 per cent., the average being a little over 1 per cent.

More accurate estimations of the true casein are obtained by
determining the amount of nitrogen, and calculating the quantity of
casein from the result.

=Keeping Properties of Butter.=—Rogers and Gray have studied the effect
of the acidity of the cream upon the flavour of butter (U.S. Dept.
Agricult., 1909, Bull. No. 119). They show that butter is liable to
develop unpleasant flavours even when stored at temperatures as low as
-10° F., and that the amount of alteration increases with the acidity
of the cream from which the butter was prepared.

No micro-organisms to which the more rapid deterioration of butter from
very acid cream could be attributed were detected, nor did the changes
appear to be due to the action of enzymes.

When the butter had been made from sterilised cream acidified with
various acids there was a gradual development of unpleasant flavours,
and this result indicated that the acid normally produced in milk
by the lactic acid bacteria had an influence in bringing about slow
decomposition of unstable compounds in the butter.

Butter made from sweet sterilised cream was found to show much less
tendency to change on storage than that made in the ordinary way, but
the flavour would as a rule be regarded as too mild.

Flavours derived from the wood of the churn, or other external sources,
would also be much more noticeable in the case of such butter than in
that made from soured cream.

This lack of flavour has been shown by Storch to be due to absence
of the products of certain bacteria which develop in the souring of
the cream, and various species have been isolated, each imparting
characteristic properties to the butter.

Thus Conn has demonstrated the practical advantages of inoculating the
cream with cultures of specific bacteria, and has shown that in this
way it is possible to give to the butter the particular flavours which
previously had only been naturally produced at certain periods of the
year. At the same time butter thus artificially ripened was found to
keep better and to retain its flavour longer than that prepared by
the older method. This method of artificial inoculation with specific
organisms has been successfully employed on a large scale in America.

Burr and Wolff (_Milchwirtschaftl. Zentralbl._, 1910, vi. 241) have
recently studied the effect of the parchment wrappings of butter upon
the keeping qualities, and have found that under certain conditions
parchment paper affords a suitable medium for the growth of moulds.

The main factors influencing this growth are a high percentage of
moisture in the butter and the access of air. The presence of 1 to 1·5
per cent. of salt checks the growth, whereas unsalted butter is readily
attacked.

A method of improving the keeping qualities of butter has been based
upon the sterilising action of ultra-violet rays upon the water used
for washing the butter in the dairy.

It has been pertinently pointed out by Dornic and Daire (_Comptes
Rend._, 1909, 149, 355) that it avails little to prepare butter
from sterilised cream if the water used for washing it contains
micro-organisms that tend to produce rancidity.

The apparatus employed by Dornic and Daire consists of a tank lined
with glass, and provided with glass partitions over which the water
passes, and receives the rays from two quartz electric lamps, which are
inserted through holes in the cover of the tank.

About 3000 litres of water can thus be rendered practically sterile
in a day, the number of bacteria being reduced by the treatment to an
insignificant quantity.

The cream, or the butter itself, might be rendered sterile by this
process, but an unpleasant flavour produced by the action of the ozone
formed by the lamps prevents the method being successfully employed in
practice.

A French patent has, however, been taken out (No. 400,921 of 1909) for
sterilising butter or other fats in this way. The substance is spread
in a thin layer upon an endless band or revolving drum, the movement of
which carries it past a series of lamps emitting ultra-violet rays.

=Rancidity of Butter.=—There appears to be little doubt that
micro-organisms may play a part in the production of rancidity in
butter, although the presence of light and air are probably the chief
factors in the changes that take place.

Laxa, who studied the question with especial reference to butter
(_Arch. Hyg._, 1902, xli. 119), found that several mould fungi, and
at least one bacillus (_B. fluorescens liquefaciens_), were capable
of growing upon media containing butter fat and of breaking up the
glycerides, with the liberation of free fatty acids, which were then in
turn decomposed.

The acidity of the fat increases with the progress of the rancidity,
but not necessarily proportionately, and a specimen of butter fat in
which the oxidation product to which the rancid taste and odour are
due may have a lower acid value than butter, which shows no trace of
rancidity.

Many of the compounds produced in the development of rancidity are
soluble, and may be separated from the fat by washing it with water.
Advantage is taken of this fact in the preparation of “process” butter
from stale or unsaleable genuine butter.

There is no definite test that can be applied to detect rancidity in
butter, and reliance must therefore be mainly placed upon the taste.

=Renovated Butter.=—A product sold in large quantities under the name
of renovated or “process” butter is prepared by melting down the fat
of old butter, separating it from the curd and water, chilling it
upon ice, and re-churning it with fresh milk and whey. By this means
the casein is restored to the butter, and a mixture is obtained which
answers to the chemical tests for fresh butter, but lacks its fresh
flavour.

Several methods are employed for distinguishing process butter from
the genuine product, the most satisfactory of which are based upon the
physical alteration of the butter fat in the processes of melting and
congealing. Thus in the case of ordinary butter the separated fat does
not show the crystalline structure of the fat from renovated butter
when examined under the microscope, and the difference is still more
pronounced when the fats are compared in polarised light.

Other tests upon which a judgment may be based are the greater
solubility of the “process” fat in glacial acetic acid (Cochrane); and
the appearance and behaviour of the separated curd, which is gelatinous
when derived from fresh butter, and granular and flocculent when
obtained from renovated butter.

Hess and Doolittle (_J. Amer. Chem. Soc._, 1900, xxii. 150) also
observed a difference in the behaviour of the two products when heated,
genuine butter foaming, while process butter splutters in the same way
as margarine, from which, however, it may be distinguished by other
tests.

The trade in process butter is much more extensive in the United States
than in this country, and numerous patents have been taken out to
obtain a product that shall imitate ordinary butter still more closely.

Among the most recent of these is the process claimed by Roos (U.S.
Pat. 854,383, 1907). The fat separated from the old butter is melted
and heated to a temperature of 108° to 110° F., and is then termed
“butter oil.”

About five parts of it are added to 3 parts of a previously churned
mixture of acidified skimmed milk and fresh whole milk, and the
whole stirred up until an emulsion is obtained. This is treated with
cold water to cause crystallisation, and the resulting crystals are
mixed with salt and exposed to the air for some time at the ordinary
temperature, after which the mass is thoroughly kneaded to expel the
salt and the excess of milk.

=Preservatives in Butter.=—Butter that at one time was heavily salted
is now frequently preserved by the addition of a small amount of borax
or other compound of boric acid.

The prevalence of the practice was shown by the evidence given
by leading representatives of the butter industry before the
Departmental Committee on Preservatives in Food (1901). One of these
witnesses informed the Committee that his firm had ceased to use heat
sterilisation of the cream, as it was found to impair the flavour of
the butter.

It was further shown that the butter imported from Australia, Normandy,
etc., contained 0·5 per cent. of boric acid; and that this amount was
regarded by the trade as sufficient for the purpose.

In their report the Committee recommended that no preservative other
than boric acid or borax, or mixtures of the two, should be permitted
to be used in butter or margarine, and that the proportion should not
exceed ½ per cent.

An attempt was made in France to prohibit absolutely the use of
preservatives in butter, but the needs of the trade were too strong,
and, as was mentioned above, the butter imported into this country from
France is almost invariably preserved.

The presence of boron compounds is proved by melting the butter,
separating the aqueous portion, rendering it faintly acid with
hydrochloric acid, and immersing a strip of turmeric paper therein.
On drying the paper at a gentle heat a purple-red coloration, changing
to bluish black on the addition of ammonia solution, indicates the
presence of boric acid.

Tests are sometimes applied for other preservatives, such as salicylic
acid, sodium benzoate, sodium fluoride, and formalin, but these
compounds are not of common occurrence in butter.

Some years ago butter intended for export to tropical countries was
preserved by the addition of a fairly large proportion of glucose. This
practice was most common in France.

=Physical Characteristics.=—Butter fat has a specific gravity ranging
from about 0·907 to about 0·913 at 35° C., whereas the specific gravity
of the animal fats used as adulterants is considerably higher.

It has been shown by Skalweit (_J. Soc. Chem. Ind._, 1894, xiii. 54)
that these differences are most pronounced at a temperature of 35° C.,
as is illustrated by the following table:—

+-------------+---------+------------+-------------+
|Temperature, | | | |
| °C. | Lard. | Margarine. | Butter Fat. |
+-------------+---------+------------+-------------+
| 35 | 0·9019 | 0·9017 | 0·9121 |
| 50 | 0·8923 | 0·8921 | 0·9017 |
| 60 | 0·8859 | 0·8857 | 0·8948 |
| 70 | 0·8795 | 0·8793 | 0·8879 |
| 80 | 0·8731 | 0·8729 | 0·8810 |
| 90 | 0·8668 | 0·8665 | 0·8741 |
| 100 | 0·8605 | 0·8601 | 0·8672 |
+-------------+---------+------------+-------------+

The specific gravity of cocoanut oil is also greater than that of
animal fats.

_Solubility._—Butter fat is considerably more soluble than animal body
fats in various solvents, such as glacial acetic acid, alcohol, etc.,
and on this property have been based several rapid “sorting” tests for
distinguishing between pure and adulterated butter.

One of these tests, known as the _Valenta test_, gives the temperature
at which a solution of a definite quantity of the fat in a definite
quantity of hot glacial acetic acid becomes turbid on cooling the
liquid.

The following figures obtained by Chattaway, Pearmain, and Moor, show
the difference between butter and margarine:—

+-----------+----------+----------+-------+
| | Maximum. | Minimum. | Mean. |
+-----------+----------+----------+-------+
|Butter fat | 39·0 | 29·0 | 36·0 |
|Margarine | 97·0 | 94·0 | 95·5 |
+-----------+----------+----------+-------+

The natural variation in this respect between different samples of
genuine butter is thus too great to permit of the detection of small
quantities of margarine in butter.

_Refractometric Examination._—The difference in the refractive power of
butter fat and margarine is a valuable means of obtaining a preliminary
idea as to the purity of a sample of butter, and several instruments
have been specially constructed for the purpose. The most widely used
of these is termed a _butyro-refractometer_, and it is readily possible
by its means to distinguish in a few minutes between pure and grossly
adulterated butter. Here again, however, the variations in the readings
of samples of genuine butter of different origin are sometimes greater
than between a sample of pure butter and one adulterated with a small
percentage of margarine. Thus Crismer found that two pure samples of
butter fat gave readings of 45·8 and 46, while two adulterated samples
gave readings of 45·2 and 45·6 at 40° C.

=Chemical Characteristics.=—Owing to the large proportion of fatty
acids of low molecular equivalent present in butter fat, the
saponification value is naturally very high, ranging from about 219
to 240, though values both above and below these figures have been
recorded for genuine butter.

Since cocoanut oil also has a high saponification value (254 to 260),
mixtures of animal fat with that fat may readily be prepared which will
give figures within the normal limits for butter fat.

The proportion of free fatty acids in freshly churned butter fat is
very small (about 0·01 grm. per kilo. according to Duclaux), but it
gradually increases as the butter is kept. A determination of the acid
value may therefore afford some indication of the age of a sample of
butter.

The iodine value of pure butter fat is usually between 25 and 40, but
is liable to fluctuate considerably with the nature of the food given
to the cows.

Of all the different so-called constants, the Hehner and Reichert
values described below are the most important as tests of purity, and
an official method of determining the latter value has been established
in this country, so as to eliminate errors due to variations in the
size of the apparatus, duration of distillation, etc.

_Hehner and Reichert Values._—The chief substances used in the
adulteration of butter are beef fat and pig’s fat (in the form of
margarine), vegetable oils (also mainly in margarine), and (especially
of late) cocoanut oil.

The methods of distinguishing between butter fat and other animal fats
are based upon the high proportion of soluble volatile fatty acids in
the former, and their practical absence from the latter.

Originally the test was devised by Hehner, who measured the amounts of
insoluble fatty acids yielded by butter fat, and showed that they were
very much less than those given by other fats.

It is now more usual, however, to employ the more rapid process devised
by Reichert (with modifications by other chemists), in which the fatty
acids are distilled under definite conditions which must be rigidly
followed, and the proportion of them thus obtained is estimated by
neutralisation with a standard solution of alkali. The details of the
method are described at length in Chapter VIII. The result is then
expressed in the number of cubic centimetres of this standard alkali,
and is termed the Reichert (or Reichert-Meissl) value of the fat.

The Reichert-Meissl value of pure butter fat has been found to vary
under ordinary conditions from about 20 to 33, though figures far
beyond either of these limits have been recorded in exceptional cases.

In calculating the amount of foreign fat in a butter from this value
it is assumed as an arbitrary figure that an average butter fat has a
Reichert-Meissl value of 28·78, and the percentage of added fat may
thus be found approximately.

The difficulty, however, is that the values normally range so widely
above and below this average, that it is quite possible to add 10 (or
more) per cent. of foreign fat to a butter with a high Reichert-Meissl
value, and still have a product giving a normal value.

On the other hand, cows frequently produce butter which gives a value
far below the standard figure, and without special knowledge of the
conditions to which this abnormality is due the butter may be condemned
as adulterated with foreign fat.

This was shown in a striking manner a few years ago, when large
quantities of butter imported into this country from Holland were
condemned as adulterated on account of their low Reichert-Meissl values.

The causes of this abnormality were investigated by van Rijn, who
found that the mixed butter of a herd of cows might vary in its
Reichert-Meissl value from 17·0 to 32·1.

The low figures were found to coincide with the end of the pasturage
season, for after the cows had been stalled for a short time the butter
became normal again. For example, the butter from a herd of seven cows
had a Reichert-Meissl value of 24·4 on September 11, which had fallen
to 19·0 on October 23. The animals were then taken from the fields, and
their butter gave the following values: November 6, 21·5; November 20,
23·1; and December 11, 25·4.

This conclusion as to the effect of leaving the cows too late in the
fields was borne out by the results of a Commission appointed to
investigate the causes of abnormality of the butter produced in Belgium.

It was found that the butter giving such results was generally the
product of small herds of cows; that its occurrence was most pronounced
in the last four months of the year; and that with the return of spring
the values became normal again.

It may be mentioned that in Belgium the sale of butter showing a lower
Reichert-Meissl figure than 28 is prohibited by law, while in the
United States the minimum value is fixed at 24.

Poor feeding has also an influence in lowering the Reichert-Meissl
value, and to this cause must be attributed the low values frequently
found in the case of Siberian butter.

Another factor influencing the degree of the Reichert-Meissl value
is the time that has elapsed since calving. Thus it was shown by
Kreit (_Analyst_, 1893, xviii. 134) that the values obtained at an
early period of lactation were invariably higher, and that they then
gradually fell. In some cases the butter from the milk of cows that had
recently calved reached the high Reichert-Meissl value of 34·4.

This also affords the explanation of the occasionally low
Reichert-Meissl values of Irish butter, which, as has been proved by
Ball (_Analyst_, 1907, xxxii. 202), coincides with a period when the
milk has been derived from cows at the very end of lactation. This
period lasts for about six weeks, during which time the milk is richest
in fat, while the fat shows the lowest Reichert-Meissl values. Thus the
following results were obtained with butters churned on December 19,
1906:—

+---------------+---------+-------+-------+--------+----------+
| |Limerick.|Bruree.|Mallow.|Clonmel.|Tipperary.|
+---------------+---------+-------+-------+--------+----------+
|Reichert-Meissl| | | | | |
| values | 22·7 | 21·5 | 23·3 | 23·5 | 22·1 |
+---------------+---------+-------+-------+--------+----------+

The same abnormality does not occur in England, where the calving of
the cows is distributed over the whole year, instead of, as in Ireland,
taking place within six weeks of one another.

It is also possible that sufficient attention may not be given to the
cows in Ireland, since the effect of feeding and good housing is to
raise the Reichert-Meissl value of the butter, even in the case of cows
at the end of their lactation period.

=Influence of the Food of the Cows.=—The results of numerous feeding
experiments, in which quantities of different oils and fats were mixed
with the daily fodder of the cows, have shown that the nature of the
butter fat may be appreciably affected in this way. Thus Werenskiold
(_Chem. Zentralbl._, 1900, ii. 215) proved that cotton-seed oil could
be detected in the fat from the milk of cows which had taken a small
amount of cotton-seed oil cake with their food, and this result was in
agreement with the results of experiments carried out for the Board of
Agriculture in this country (_Analyst_, 1898, xxiii. 255).

As a rule, however, the colour reaction indicating the presence of
cotton-seed oil is very slight, and does not correspond to a proportion
of more than 1 per cent.

In the corresponding experiments of the Agricultural Board with sesame
oil cake the butter from the cows did not give the characteristic
colour reaction for that oil, even after they had been fed upon it for
several weeks.

There is also evidence to show that the characteristic fatty acid of
arachis oil does not pass into the milk of cows fed upon arachis-seed
cake; but it has been shown by Paal and Amberger (_Zeit. Unters. Nahr.
Genussm._, 1909, xvii. 1) that feeding the animals upon copra may have
some influence upon the composition of their milk fat, and increase the
proportion of insoluble volatile fatty acids.

Opinion is divided as to the advisability of having a fixed standard
for a chemical property such as the Reichert value. Although such
a limit as is fixed in Belgium excludes all doubt in condemning
samples that fall below it, yet, as was found in the case of lard (p.
64), a fixed standard leads to an increase in the amount of petty
adulteration, since it is not difficult for a skilful mixture to be
made that will answer the requirements of a moderate standard.

In any case there is even now a systematic attempt to conform with what
the adulterator presumes will be the standard by which the analyst
will judge his product, and the present writer has frequently examined
samples with a Reichert-Meissl value of 23-24 which in all probability
contained a small quantity of foreign fat, but yet might conceivably
have been genuine butter containing less than the average quantity of
volatile fatty acids.

Nor does it follow that such butter is necessarily inferior as a food,
for there is no proof that a slight deficiency in the amount of the
glycerides of volatile fatty acids affects the nutritive value of the
whole fat.

=Cocoanut Oil in Butter.=—The addition of cocoanut oil to butter, which
has become increasingly prevalent of late years, has the effect of
lowering the Reichert-Meissl value to a much smaller extent than the
addition of animal fat.

This is due to the fact that cocoanut oil has itself a Reichert-Meissl
value of 7-8, indicating the presence of a considerable amount of
soluble volatile fatty acids, and it is therefore possible to prepare a
mixture of animal fat, cocoanut oil, and fluid vegetable oil, which can
be added to butter in a fairly large proportion without reducing the
Reichert-Meissl value of the latter below 24 or 25.

The problem of detecting cocoanut oil in butter has therefore received
much attention of late, and numerous methods have been devised for
estimating the amount of such addition.

Speaking generally, these are based upon the fact that cocoanut oil
contains a high percentage of lauric acid (up to 60 per cent.), whereas
that acid is only present in very small proportion in butter fat.

Now, since lauric acid will volatilise in a current of steam, but,
unlike the lower fatty acids (butyric, caproic, caprylic, and capric
acids), is not soluble in water, it is possible to obtain a measure of
its proportion by continuing the distillation as in the Reichert-Meissl
process until the whole of the volatile fatty acids (soluble and
insoluble) have passed over. The distillate, when filtered, is
separated into a soluble and insoluble portion, and the latter may
be dissolved in alcohol and its acidity determined by titration with
standard alkali solution.

A method whereby the process of distillation is greatly accelerated is
described in Chapter VIII.

Other methods of detecting cocoanut oil have been based upon the
quantitative separation of the lauric acid in the form of various
metallic salts, such as barium, cadmium, etc., so as to obtain
“barium values,” “cadmium values,” etc., which will increase with the
proportion of cocoanut oil in the butter.

These methods, however, are more complicated and no more effective than
the method of extended distillation, although they are of value as
affording confirmatory evidence of the adulteration (see p. 116).

=Artificial Colouring Matters.=—The nature of the food given to the
cows, their breed, and the season of the year, all have an influence
upon the colour of the butter; that produced in summer, for instance,
being more yellow than that produced later in the year.

When exposed to the action of air and light the natural colour of
butter gradually fades, and ultimately the fat becomes colourless.

The popular demand for a butter of pronounced yellow colour—a demand
inspired by the belief that intensity of colour indicates purity—has
led to the artificial colouring of pale butter.

The colouring matters employed for this purpose include that of the
carrot, annatto, turmeric, saffron, marigold, and various aniline
dye-stuffs.

Special azo dye-stuffs, soluble in oil, are frequently used, especially
in the United States. They may be detected by mixing a little fuller’s
earth with the butter-fat which has been separated from the curd, the
earth assuming a pink or light red coloration in the presence of such
dyes.

Since in the United States the sale of margarine containing artificial
colouring matters is prohibited, the desired yellow colour is now
frequently obtained by the use of palm oil, mustard-seed oil, and
similar fats of intense colour. Special tests have therefore been
devised for the detection of these fats in butter.

CHAPTER V

LARD

=Rendering of Lard.=—Lard may be defined as the fat separated for use
as food from the adipose tissue of the pig.

In the process of rendering lard the tissue is first finely divided or
minced in a machine, or is crushed between rollers, and is then heated
either by dry heat or by means of steam to expel the fat from the
ruptured fat-cells.

A product of excellent quality is obtained by subjecting the mass
to dry heat at a temperature just sufficient to melt the fat; and a
process of this kind is frequently used in the preparation of the fat
for margarine.

At higher temperatures some decomposition of nitrogenous compounds in
the adipose tissue takes place, and special means must be provided for
carrying off the obnoxious vapours thus produced.

The use of steam in a steam-jacketed pan or digester enables the
temperature to be regulated with greater nicety, and prevents the fat
being overheated and acquiring a burnt flavour.

A more rapid process of rendering lard is to heat the finely divided
material with water in a suitable vessel and subsequently to skim off
the fat that rises to the surface. At first the temperature is kept as
low as possible in order to separate the portions of the fat of lowest
melting-point. Then the temperature is raised, with the result that a
fat of greater consistency rises to the surface; and finally the water
is brought to the boiling-point to separate, as far as is possible by
this means, the residual fat. In this way a fractionation of the lard
takes place.

A process more frequently employed than the preceding one is that in
which the adipose tissue is rendered, in a closed vessel or digester,
capable of resisting the action of steam introduced under pressure.

Numerous patents for apparatus embodying this principle have been taken
out, especially in the United States, various modifications of the mode
of heating, separation of the fat, and filtration being claimed.

In some of the largest works in Chicago and other centres of the
American lard industry a great number of such digesters is employed,
some of them having a capacity of upwards of 20,000 gallons. Each of
these vessels is reserved for its particular kind of fat, so as to
facilitate the speed of working.

In a typical digester the finely minced fatty matter, which has been
separated from the recently killed animal, is introduced from above
through a man-hole, which is then screwed down hermetically. Within the
digester is a perforated false bottom upon which the material rests,
and beneath this is a perforated steam coil, connected by means of
a pipe with an outside boiler, from which steam is admitted until a
pressure of about four atmospheres is shown upon the gauge. Condensed
water is drawn off through a cock near the bottom of the vessel, while
a similar cock is provided near the top for testing whether the fat
is being liberated. After a digestion of about twelve hours the steam
supply is shut off, and the pressure in the digester reduced by opening
the safety valve. Then, after standing for some time for separation
to take place, the aqueous layer is drawn off through taps arranged
at different levels near the bottom. The rendered fat, which has
separated on the surface as a melted layer, is next withdrawn, and
finally the residual mass is expelled through an outlet in the bottom,
which can be controlled from above by a rod passing through the body of
the apparatus.

=Commercial Grades.=—In the United States (which probably produces more
lard than the rest of the world put together) various grades of lard
are recognised, depending mainly upon the part of the animal whence
they were derived. Thus, according to Wiley (U.S. Dept. Agriculture,
Bull. 13), the following descriptions of lard are known in the trade:—

(1) _Neutral lard_, which is the product of the absolutely fresh leaf
of the hog, rendered at a temperature between 105° and 120° F. It is
chiefly used in the manufacture of margarine.

(2) _Leaf lard_, prepared from the residue left after removal of
neutral lard at a lower temperature.

(3) _Choice steam lard_, or _Choice lard_, obtained from the residual
tissue from neutral lard and from adipose tissue from the back of the
animal.

(4) _Prime steam lard_, which may be the product of any part of the
animal, and especially of the fatty tissue from the head, heart, and
intestines.

(5) _Guts_, a low grade of lard rendered from scraps from any part of
the animal, with the exception of the heart and lungs.

In addition to these, still lower grades of pigs’ fat, which are
used for soap and other technical purposes, are separated from hogs
that have died on their way to the slaughter-houses, or from refuse
material. These include _white_, _brown_, and _yellow grease_, and
_pigs’ foot grease_.

The product known in Germany as _pure lard_ is obtained by a process of
steam-rendering, followed by mechanical agitation of the separated fat
in a closed vessel until it begins to solidify. An addition of a small
proportion of a more solid lard is then made, or, in the best grades,
a small proportion of lard stearin is added. According to Voigtländer
(_Zeit. angew. Chem._, 1898, 857), this treatment, which is known as
the Hungarian process, prevents the lard becoming fluid on keeping.

American lard, even when free from any addition of vegetable oil, is
often of a more fluid character than European lard, this being due
partly to differences inherent in the hogs and partly to the influence
of the food given to the animals.

=Composition.=—Lard, like most natural products, shows wide variations
in its chemical and physical characteristics, and this increases the
difficulty of basing definite conclusions as to purity on the results
of analyses. Even in the case of the same animal wide variations are
observed in the composition of fat taken from different parts of the
body, as is shown below.

Chemically considered, lard may be said to consist of glycerides of
stearic, palmitic, lauric, and myristic acids, and of the liquid fatty
acids, oleic and linolic acids; and the different physical properties
of different samples of lard are due, in the main, to variations in the
proportions of these different constituents. For instance, the firm fat
from the leaf or kidneys of the animal contains fatty acids with a low
percentage (about 15 per cent.) of stearic acid, and a high percentage
(about 58 per cent.) of oleic acid; whereas the fat from the neck and
back, which is very soft, contains fatty acids with about 9 per cent.
of stearic acid, and about 75 per cent. of oleic acid.

=Lard Crystals.=—A curious property of lard, upon which reliance has
often been placed as a test of purity, is that when it is dissolved in
ether and the solution is gradually allowed to evaporate, crystals of
characteristic form are often produced.

The fat crystals from an ordinary soft lard have flat edges and
chisel-shaped ends, whereas the similar crystals from beef fat are
in the form of bunches of needle-shaped crystals. A small proportion
of beef fat added to a soft lard influences the crystallisation
sufficiently to produce bunches of needle-shaped crystals, though
chisel-ended crystals may also be detected.

Unfortunately for the purpose of this test, flare or leaf lard may also
produce crystals which very closely resemble those derived from beef
fat, and this resemblance is rendered closer by re-crystallisation, so
much so that in some cases the two kinds of crystals are practically
indistinguishable.

Hehner and the writer (Mitchell) found that the needle-shaped crystals
contained a higher proportion of stearic acid than the chisel-ended
crystals, and attributed the characteristic differences to this fact.
It has been shown, however, by Kreis and Hafner that the difference is
due to the characteristic flat crystals of lard consisting of a mixed
glyceride heptadecyldistearin, whereas the crystals from beef and
mutton fat consist of another mixed glyceride, palmitodistearin.

According to Dunlop, it is possible, by continued re-crystallisation of
beef fat crystals, to obtain eventually a deposit containing crystals
which are practically indistinguishable from those given by an ordinary
lard.

From all this it will be seen that there is considerable risk of making
a mistake, if judgment of the purity of lard is based solely upon the
form of the crystals, as has sometimes been done. The fact that the
crystals are chisel-shaped may be regarded as presumptive evidence of
the purity of a lard, but the occurrence of bunches of needle-shaped
crystals does not necessarily indicate an addition of beef fat.

=Influence of Food.=—A point of considerable importance to the
manufacturer of lard is that the food given to the animal may have a
pronounced influence upon the composition and chemical reactions of the
lard.

The fat of the wild boar differs from that of the domestic hog in being
of a much more fluid nature. There is also some difference between the
fat of wild and domestic hogs, the former containing a greater amount
of unsaturated glycerides.

The more fluid character of American lards as compared with European
products is to be attributed, in part at all events, to the animals
being fed upon cotton-seed cake.

It has been shown by Dunlop, however (_J. Soc. Chem. Ind._, 1906, xxv.
459), that hogs fed upon cotton-seed cake give lard yielding pronounced
colour reactions for cotton-seed oil, but not, judging by the iodine
value, containing an abnormal amount of fluid fatty acids.

Animals fed upon cocoanut oil cake (copra) also show the influence of
the food in their lard, which, without special knowledge of this fact,
would certainly be condemned as having been adulterated with that
vegetable fat.

This is shown in the following analytical values of lards from
Philippine hogs to which a daily supply of cocoanut oil cake had been
given (Gibbs and Agcaoili, _Philippine J. Science_, 1910, v. 33):—

+---------------------+---------+--------+------+--------+----------+
| | Refract-|Saponif-| | Iodine | Melting- |
| | ometer |ication |Iodine| Value | point |
| Lard. | reading | Value. |Value.|of Fatty| of Fatty |
| |at 40° C.| | | Acids. |Acids. °C.|
+---------------------+---------+--------+------+--------+----------+
|From maize-fed hogs:—| | | | | |
| Maximum | 46·0 | 199·0 | 52·7 | 53·8 | 43·8 |
| Minimum | 42·5 | 196·0 | 46·7 | 50·0 | 41·6 |
| Mean | 44·7 | 196·9 | 49·4 | 51·7 | 42·7 |
|From copra-fed hogs:—| | | | | |
| Maximum | 47·0 | 213·7 | 42·5 | 46·2 | 42·3 |
| Minimum | 44·0 | 204·6 | 32·5 | 36·2 | 39·4 |
| Mean | 45·3 | 208·9 | 37·7 | 41·3 | 40·4 |
+---------------------+---------+--------+------+--------+----------+

=Acidity of Lard.=—In order to obtain a practically neutral product,
the fat intended for lard should be rendered as soon as possible
after the animal has been killed. After standing for some time, the
fat in the adipose tissue gradually undergoes decomposition, with the
liberation of free fatty acids, and the acidity steadily rises. In
refined lard the process of hydrolysis is greatly checked through the
removal of nitrogenous substances, but the development of acidity will
continue when the fat is exposed to the influence of light and air.

As a rule, a freshly prepared lard does not contain more than 0·5
per cent. of free fatty acids (as oleic acid), and frequently the
proportion is very much lower. Thus the acidity of fats from the leaf
and kidneys of six Philippine hogs examined by Gibbs and Agcaoili
(_loc. cit._) ranged from 0·28 to 0·38 per cent. On the other hand, the
intestinal fat contained considerably more free fatty acids (0·86 per
cent.). Samples of American lards examined by Wiley (_loc. cit._) had
an acidity ranging from 0·35 to 1·0 per cent. An acidity in excess of 1
per cent. probably indicates either that the lard was not prepared from
fresh material or that it has been exposed to the air for some time.

=Water.=—Lard should not contain more than a small proportion (0·75 per
cent. at most) of water, and as a rule most commercial samples contain
considerably less than 0·5 per cent.

Polenske (_Arb. a. d. Kaiser. Gesundheitsamte_, 1907, xxv. 505)
found that there was a relationship between the temperature at which
the melted fat became turbid on cooling and the proportion of water
present, and on this fact based a rapid method of estimating the
moisture. Thus the following figures were obtained by Fischer and
Schellens (_Z. Unters. Nahr. Genussm._, 1908, xvi. 161):—

+--------------------------+----+----+----+----+----+----+----+
| Water, per cent. |0·45|0·40|0·35|0·30|0·25|0·20|0·15|
| Turbidity Temperature °C.|95·2|90·8|85·0|75·8|64·6|53·2|41·2|
+--------------------------+----+----+----+----+----+----+----+

In their opinion, based upon the examination of a large number of
German lards, the proportion of water should be less than 0·3 per
cent., corresponding to a turbidity temperature not exceeding 75° C.

Gross adulteration of lard with water is no longer a common practice.

=The Iodine Value.=—Important information as to the purity of lard is
sometimes afforded by a determination of the percentage of iodine with
which it will combine.

As a rule, European lards have iodine values not exceeding 61, and an
iodine value considerably in excess of that figure, say 66, suggests
the addition of cotton-seed oil or of other vegetable oils with high
iodine values.

From what has been stated above, however, it will be seen that
an abnormal iodine value is not in itself sufficient proof of
adulteration, since American lards of genuine character may show that
characteristic.

The differences in this respect between American and German lards are
attributed by Voigtländer (_loc. cit._) to the fact that American lards
contain a large proportion of lard oil of a more unsaturated character.
Thus, while German lard contains only about 50 per cent. of lard oil
with an iodine value of 70-75, American lard may contain about 60 per
cent. of lard oil with an iodine value of 88.

Some of the semi-fluid Russian lards sold in Germany contain as much as
90 per cent. of lard oil.

Of 100 samples of American lard imported into Germany, 88·5 per cent.
had an iodine value between 61 and 66, and 41 per cent. a value
exceeding 64.

The fixing of a standard for the iodine value of lard is unlikely to
result in the sale of a purer product, judging by the experience of
places where such a standard has been fixed. Thus at one time 62 was
fixed as the limit for the iodine value in Bavaria, and the result was
a widespread addition of beef stearin to make the lards answer to this
requirement.

=Lard Oil.=—The fluid portion expressed from lard in the separation of
lard stearin is known as _lard oil_.

It has a soft, pleasant taste, and, being almost free from odour, forms
a good edible oil.

It consists in the main of olein, with a small proportion of glycerides
of solid fatty acids, chiefly palmitic acid. A typical sample will have
values similar to the following:—

+--------+--------------+------+------+--------------+-------------+
| Sp. gr.| | | | |Melting-point|
| at |Saponification|Hehner|Iodine|Solidification| of |
|15·5° C.| Value. |Value.|Value.| point. | Fatty Acids.|
+--------+--------------+------+------+--------------+-------------+
| 0·914 | 194 | 97 | 76 | -4° C. to | 35° C. |
| | | | | +10° C. | |
+--------+--------------+------+------+--------------+-------------+

It is thus evident that a large amount of lard oil can be added to
olive oil without making the values of the mixture abnormal.

It also gives a similar product in the elaidin test, and the
phytosterol test (p. 101) is probably the best means of detecting it.

In turn it is liable to be adulterated with cheaper vegetable oils,
such as arachis, cotton-seed, and sesame oils, the presence of each of
which would be shown by their special tests. The oleo-refractometer is
also a means of determining the purity, since the ordinary reading of
lard oil, which ranges from about -1° to +5°, would be increased by
most of the oils employed as adulterants (with the exception of other
animal oils and arachis oil).

CHAPTER VI

MARGARINE AND OTHER BUTTER SUBSTITUTES

Margarine, Oleomargarine, or Artificial Butter—Invention
and Development—Modern Processes and Formulæ—Vegetable
Butter.

It has already been pointed out in Chapter I. how essential in all
except very hot countries is a fair proportion of fat in the human
diet, and, prior to the introduction of artificial butter, this could
only be largely made up among the poorer classes of the community by
the use of “dripping,” the price of genuine butter being prohibitive.
Realising the importance of the subject, the French Government in 1869
offered a prize for the discovery of an artificial substitute for
butter, which should not only be cheaper, but also remain free from
rancidity for a longer period than butter. This led M. Mège-Mouries, a
French chemist, to investigate the whole question of the formation of
fat in milk, and he was successful in securing the prize. Physiological
experiments soon led him to the conclusion that in the series of
transformations by which the butter fat is produced in the animal
economy, the carbohydrate matter consumed by the animal is first
converted into fat, and this in turn, after being deprived of much of
the stearin it contains, by respiratory combustion, is changed by the
digestive action of pepsin into butter fat, and a method was devised
for effecting this latter process artificially.

The original plan adopted by M. Mège-Mouries was to take 1000 kilos
of fresh beef fat, preferably from the kidney or intestines, and
after thoroughly comminuting it and freeing it from tissue, to warm
it at 45° C. with 300 kilos of water, 1 kilo of carbonate of soda,
and two sheep’s or pigs’ stomachs for two hours, when, under the
action of the pepsin, the fat separated completely from any remaining
tissue, and came to the surface as a homogeneous fluid. This was then
decanted into a second vessel warmed to 45° C., and washed with a 2
per cent. solution of common salt, which prevented any fermentation.
After allowing it to stand, a limpid yellow fat separated, having a
butter-like odour, and on cooling to 20-25° C., this crystallised to a
semi-solid mass, with a granular structure which, when the fat was cut
in thicknesses of half an inch, wrapped in linen cloths, and subjected
to a moderate hydraulic pressure between hot plates, at a temperature
of 25° C., allowed 50 to 60 per cent. of a soft fat, comparatively free
from stearin, to be expressed.

This fluid fat, or “oleomargarine,” as it was called, solidified on
cooling, and constitutes what was originally sold in Paris under the
name of “Margarine.”

This soft fat was next converted by Mège-Mouries into a product more
closely resembling natural butter by churning it for two hours with 10
per cent. of cow’s milk, and water in which was macerated 0·4 per cent.
of cow’s udder, complete emulsification being effected by the action of
the pepsin and the churning. After washing with cold water, salting,
colouring with annatto, and finishing off as with ordinary butter, a
very good imitation of the natural article was obtained.

According to Boudet, this artificial butter has a melting-point of 17
to 20° C., contains about 12·5 per cent. of water, and, in the dry
state, 1·20 per cent. of insoluble casein, and is less liable to become
rancid than natural tallow.

Factories were soon erected at Poissy and at Liesing, near Vienna, to
work the process, which was patented by Hippolyte Mège-Mouries, in
England, in 1873. The English patent claimed a process for preparing
artificial butter by mixing the oleomargarine with water containing
sodium bicarbonate, casein, and mammary tissue. The sale of artificial
butter was authorised by the Council of Hygiene of Paris in 1872, the
use of the name “butter” to describe it being prohibited.

The name “margarine” was first applied by Chevreul to what was at
that time considered to be a definite single compound of margaric
acid with glycerin, and found in human fat and olive oil. Subsequent
research by Heinz has shown, however, that so-called margaric acid
is in reality a mixture of stearic and palmitic acids, and the term
“margarine” does not therefore represent any definite chemical body.
The name “oleomargarine” was introduced to signify what was believed
to be a mixture of olein and margarine from which the stearin had
been separated. Part of the “margarine” is now known to consist of
stearin and palmitin, so that the oleomargarine still contains these
two glycerides, though to a much smaller extent than in the original
beef or mutton fat. The softer fat, from which the stearin has been
removed, is known in America as “oleo oil,” the artificial butter made
therefrom being termed “oleomargarine.” In this country it was decreed
by the Margarine Act of 1887 that all artificial butter should be
sold under the name of “margarine,” and this has long since become a
well-established, popular name, such terms as “butterine,” and “Dutch
butter,” which had gradually come into use, being declared illegal by
this Act.

The successful working of the Mège-Mouries process quickly led a number
of other investigators to take up the subject of the production of
artificial butter, and the next few years following were prolific in
patents for the purpose.

Among many others, Lake, in 1871, patented the admixture of cotton-seed
oil; E. G. Brewer, in 1874, the churning of treated tallow with 3 to 4
per cent. of sour milk and 2 per cent. of oil; and Pitt, in 1877, the
addition of arachis oil; Mège the same year obtaining a further patent
for the use of an artificial gastric juice, consisting of hydrochloric
acid and acid phosphate of lime, to help in the artificial digestion of
the fat.

In spite of these, the method of margarine manufacture does not appear
to have undergone much change, and is to-day in most respects closely
similar to that originally proposed by Mège, with the exception that
the artificial digestion of the fat is now dispensed with, and a
certain proportion of vegetable oils is generally added.

In this country the oleomargarine, or basis of artificial butter,
consists usually of the softer portion of tallow or “premier jus,” but
in America a very large part of this, which after further treatment
is there known as “oleo oil,” is replaced by “neutral lard” obtained
from the perfectly fresh leaf, or kidney and bowel, fat of the pig. The
preparation of the “neutral lard” is almost identical with that adopted
for tallow, and as the latter is invariably employed in this country,
the modern preparation of margarine with this as a basis will now be
described.

=Modern Process.=—The carefully selected caul fat of freshly slain oxen
is first washed in a vat with warm water to remove blood and tissue,
then hardened by chilling with ice water, and thoroughly comminuted by
passage through rollers or cutting machines. It is next transferred
to tin-lined and steam-jacketed vessels, in which it is raised to a
temperature of about 40 to 45° C., when the softer portions of the
tallow melt and rise to the surface, the separation being facilitated
by sprinkling salt over the surface.

This clear oil, which is known as “premier jus,” is then siphoned off
into a second series of steam-jacketed vessels, in which it is raised
to about 45° C., after which more salt is added, and a further settling
takes place. The clear, super-natant oil is next transferred to shallow
wooden vats, in which it is allowed to stand for three to five days
at a temperature not exceeding 20° C., in order to crystallise out
the stearin, after which it is thoroughly mixed, wrapped in canvas
cloths, and subjected to pressure, whereby the soft “oleo oil,” or
oleomargarine, is separated from the harder stearin or oleo-stearin,
which is used in the manufacture of lard substitutes, or sometimes in
margarine in place of part of the oleomargarine, when a large quantity
of vegetable oils has been employed.

The oleo oil is then removed to churns, in which it is mixed with
“neutral lard,” cotton-seed oil, olive oil, sesame oil, maize oil, or
other vegetable oil, and milk (fresh or sour) or cream, or sometimes
water, a certain proportion of butter being frequently added to impart
a better flavour to the margarine.

The churning is frequently carried out in special vessels fitted with
internal agitators, and a novel form of these has been patented by
Schroeder (Eng. Pat. 25,404, 1905), in which the blades rotating at
a high speed gradually convert the ingredients into a cohesive and
homogeneous emulsion, which is forced out at the bottom of the vessel.

After churning until completely emulsified, the mixed fat is drawn off
into tubs containing pounded ice, which cool it rapidly and so prevent
crystallisation. It is then coloured with annatto or other colouring
matter, and after salting if desired, is finished off in the same way
as ordinary butter.

The number of materials available renders a very large variety of
combinations possible, and, naturally, successful formulæ used by
private firms are kept secret. The following formulæ were published,
however, by the United States Census Report for 1900:—

CHEAP GRADE.

Oleo oil 495 parts
Neutral lard 265 ”
Cotton-seed oil 315 ”
Milk 255 ”
Salt 120 ”
Colouring matter 1¼ ”

which is sufficient to produce 1265 to 1300 parts.

MEDIUM HIGH GRADE.

Oleo oil 315 parts
Neutral lard 500 ”
Cotton-seed oil 280 ”
Milk 280 ”
Salt 120 ”
Colouring matter 1½ ”

producing 1050 to 1080 parts.

HIGH GRADE.

Oleo oil 100 parts
Neutral lard 130 ”
Butter 95 ”
Salt 32 ”
Colouring matter ½ ”

producing about 325 parts.

Such a formula as this would not be permissible in this country, where
the maximum addition of butter to margarine is fixed by law at 10 per
cent., and the neutral lard is more usually replaced over here by
oleomargarine or “oleo oil,” a suitable formula being as follows:—

Oleomargarine 230 parts
Cotton-seed oil 40 ”
Olive oil 20 ”
Butter 30 ”
Salt 32 ”
Colouring matter ½ ”

The proportion of cotton-seed oil should not, speaking generally,
exceed more than about 25 per cent., or its characteristic flavour
becomes apparent. Besides cotton-seed and olive oils, arachis, palm
nut, and cocoanut oils now enter frequently into the composition of
margarine, and in Germany the use of sesame oil to the extent of 10 per
cent. has been compulsory since 1897. Palm oil, which imparts a yellow
tint to the margarine, is also occasionally incorporated. This being a
firm fat enables the proportion of animal fat to be reduced.

The colouring matter usually employed is annatto, but turmeric and
saffron are also occasionally used. The use of mineral colours is most
objectionable, and coal tar colouring matters are to be discouraged,
though azo dyes are occasionally met with.

Glycerin is sometimes added to margarine to impart a glossy appearance,
and sugar or glucose to sweeten it or improve its texture, though this
is said to injure its keeping qualities.

Many methods have been devised for causing margarine to froth and
become brown when heated, as does genuine butter. The addition of
a fair proportion of butter will, of course, secure this, but in
the absence of butter it may be accomplished by adding a sufficient
quantity of milk. The introduction of casein, lecithin, or cholesterol
has been suggested for the purpose, and Fendler has patented the
use of 0·5 per cent. of egg yolk, subsequent patentees claiming the
preliminary emulsification of the egg yolk with salt solution, lactic
acid, etc. Mitscherlich has recently patented the addition of meat
extract or yeast.

Though not really necessary in a properly made margarine, various
artificial flavourings are occasionally added, ostensibly to render the
flavour more similar to that of genuine butter, but more probably, in
many cases, to enable a proportion of the margarine to be used in the
adulteration of butter without detection by the usual chemical methods.
Such flavouring materials include butyric acid or other volatile fatty
acid, and certain butyrates, these being dissolved in glycerin or oil,
and added in this way to the margarine. Coumarin is also said to be
used, and H. A. Snelling recently patented the addition of banana fruit
or banana essence.

=Vegetable Butter.=—During the last few years a number of products
have appeared on the market under the names of “Vegetable Butter”
or “Nut Butter.” These consist chiefly of carefully refined and
deodorised cocoanut oil and palm-kernel oil, materials which have
lately been supplemented by the addition of margosa oil, shea butter,
and mowrah-seed oil. Any suitable mixture of these may be churned with
milk, coloured, and salted, and finished off like genuine butter.

=Palm Oil.=—Palm-kernel oil has long been utilised as an edible fat,
but hitherto all attempts to make use of any considerable quantity of
the fat from the pulp of the fruit (palm oil) have proved unsuccessful.

This is not on account of the deep orange colour of the fat, which
could be readily removed by oxidation, but owing to the high proportion
of free fatty acids.

The cause of this drawback has been shown by Fickendey (_Der
Tropenpflanzer_, 1910, xiv. 566) to be due to the presence of an enzyme
in the fresh fruit. For instance, the fat extracted from perfectly
fresh fruit had an acid value of 94·5-116, which became still higher
if the fruit was allowed to stand for twenty-four hours before the
extraction of the fat.

By heating the fruit this enzyme is destroyed, and the fat will then
show a low acid value. Thus in four instances in which this was done
the acid value did not exceed 5·3.

Fickendey concludes from these experiments that it would be quite
possible to put a palm oil of good quality upon the market, provided
that the following conditions were observed:—(1) Expression of fresh,
completely ripe fruit; (2) destruction of the enzyme by boiling; (3)
rapid treatment of the fruit. The last condition is essential, owing to
the readiness with which micro-organisms will decompose the fat in the
heated fruit.

CHAPTER VII

SALAD OILS

Salad Oils—Oils used for Culinary and Confectionery Purposes— Chocolate
Fats.

=Olive Oil.=—No oil is so extensively used in the preparation of salad
dressings as olive oil, and the more closely its characteristics can be
imitated by other salad oils the greater is the demand for the latter.

There are several species of the olive tree, some of which are
successfully cultivated in hot climates, but the oil used in Europe is
mainly derived from different varieties of _Olea europæa_. The fruit
produced by these varies considerably in size and in colour, but the
oils that they yield show a close similarity in chemical and physical
characteristics, though they differ from one another in flavour and in
colour.

Apart from the influence of soil and climate and of the variety of
the olive tree, the flavour of the oil also depends upon the stage of
growth at which the fruit is gathered and upon the method of separating
the oil from the pulp.

Fruit that is picked before it is quite ripe yields an oil with a
somewhat bitter flavour, and therefore in preparing the finest grade
of oil the olives are specially selected and pressed by hand between
cloths. The resulting oil is washed with water to remove impurities,
then decanted from the aqueous layer, and sold under the name of
_virgin oil_.

The bulk of fine commercial olive oil, however, is separated by
expression, the ripe olives being superficially crushed between
mill-stones, and then expressed at a low pressure. The residue left
in the press is broken up, mixed with hot water, and the liquid,
consisting of the mixed oil and water, expelled by stronger pressure,
and allowed to stand for the oil to separate. The flavour and colour of
this oil is inferior to that of the cold-drawn product.

Subsequent grinding of this second residue, followed by another
expression with hot water, yields an additional quantity of oil,
while the amount still present is often extracted by means of carbon
bisulphide or other volatile solvent. The oils finally obtained are
generally utilised as lubricants or in the manufacture of soap.

In most districts care is taken not to crush the olive stones until
after the finest oil has been expressed, although according to
Klein (_Zeit. angew. Chem._, 1898, 847) there is no disadvantage in
expressing the mixed kernel and fruit oil, provided the fruit is
freshly picked. The general opinion of the trade, however, is that the
flavour of the pulp oil is superior to that derived from the mixed pulp
and kernels.

Oils that have been extracted by means of carbon bisulphide are known
as “sulphocarbon” oils, while those which have been separated by means
of petroleum spirit are termed “pyrene” oils.

The oils derived from olives that have been left for some time before
expression are of an inferior kind, and are termed _huiles d’enfer_,
_huiles tournantes_, etc. They contain a large amount of free fatty
acids, and have a sharp, unpleasant flavour which renders them
unsuitable for food.

The finest qualities of oil are derived from the districts round Lucca
and Leghorn, and from Provence. Large quantities of excellent oil
are also exported from Spain, Portugal, Algiers, and Tunis, while
California has now become an important oil-producing country.

The flavour is the chief criterion of the quality of olive oil, and a
trained palate is able to detect slight differences which could not be
recognised by any chemical tests.

The so-called _virgin oil_ is pale yellowish-green in colour, and has
but little odour, whereas the lower grades of oil obtained from the
_marc_ left in the press, as described above, vary in colour from
greenish-yellow to light brown, and have a perceptible odour and a
somewhat bitter flavour.

Even the purest olive oil will yield a deposit of “stearin” when
exposed to a low temperature, but the amount varies with the kind
of olive which yielded the oil. Thus it is particularly abundant in
the case of Tunisian and Algerian oils, and it is therefore usual to
remove a portion of this solid fat before putting the oil upon the
market, under the name of “demargarinated” oil. The amount of “stearin”
thus removed depends upon the temperature to which the oil is chilled
before being pressed in a filter-press. Oils thus treated are sometimes
described as “winter oils” (see Chapter III.).

Olive oil consists chiefly of olein, with smaller quantities of the
glycerides of linolic acid and of various solid fatty acids (mainly
palmitic acid) which form the insoluble deposit—the so-called “stearin.”

It belongs to the class of non-drying oils, and hence does not form a
skin on its surface when exposed to the air, and when spread in a thin
film upon glass takes many days to dry up. In this respect it differs
from the semi-drying oils—cotton-seed, sesame, and maize oils—which
are frequently sold as salad oils, sometimes under descriptions that
suggest that they are olive oil.

The chief analytical characteristics of a typical olive oil are as
follows:—

+--------+----------------+--------+--------+---------------+
| | | | | Melting-point |
|Sp. gr. | Saponification | Iodine | Hehner | of |
| | Value. | Value. | Value. | Fatty Acids. |
+--------+----------------+--------+--------+---------------+
| 0·918 | 191 | 82 | 95 | 24° C. |
+--------+----------------+--------+--------+---------------+

Olive oil is very frequently adulterated, the principal substances used
for the purpose being cotton-seed, sesame, maize, and lard oils. The
vegetable oils may be detected by their general analytical values, and
the two first by the characteristic colour reaction (see Chapter VIII.
pp. 105 and 107), whilst lard oil may be detected by the cholesterol
test (p. 101).

=Arachis Oil.=—The chief centre of the arachis oil industry is the
South of France, and at Marseilles in particular enormous quantities of
the nuts are expressed.

The oil obtained by the first expression in the cold is a pale yellow
fluid which is extensively used as a salad oil. A large proportion of
the oil obtained on subsequent expression is sold as a lower grade
of salad oil, while the remainder, and also the oil obtained by hot
pressure, is manufactured into soap. The total yield of oil is from 45
to 50 per cent.

As a rule, the salad oils (which are sometimes sold as “nut salad oil”)
have a distinct odour and flavour of the nut, but in the very finest
grades, which also have but little colour, this flavour is hardly
noticeable in the case of the freshly prepared product. Arachis oil
becomes turbid at a much higher temperature and throws down a more
abundant deposit of “stearin” than olive oil, and this has greatly
interfered with its popularity as a salad oil in this country. The
solidification point is usually about +2 to +3° C. Chemically it
consists of the glycerides of hypogæic, oleic, linolic, palmitic,
stearic, arachidic, and lignoceric acids. The most characteristic
constituents are the two last fatty acids (amounting to about 5
per cent.). They are only slightly soluble in cold alcohol, and on
this property are based several methods of separating them and of
calculating from the result the proportion of arachis oil in, for
example, an adulterated olive oil.

The physical and chemical constants of arachis oil vary considerably,
as is shown in the following figures recorded by Sadtler and by
Crossley and Le Sueur for oils of different origin:—

LEGEND:
(A) = Saponification Value.
(B) = Reichert-Meissl Value.
+----------+---------+-------+--------+-------+-----------+--------+
| | | | | | |Melting |
| | Sp. gr. | | | | Free Acid |point of|
| Oil. | at | (A) | Iodine | (B) | (as | Fatty |
| | 15° C. | | Value. | |Oleic Acid)| Acids, |
| | | | | | per cent. | °C. |
+----------+---------+-------+--------+-------+-----------+--------+
|Virginian | 0·917 | 192·5 | 91·7 | 0·48 | 0·55 | 29 |
|Spanish | 0·9175 | 190·7 | 94·2 | 1·60 | 0·79 | 34 |
|African | 0·911 | 194·0 | 85·6 | | 0·62 | 30 |
|Indian | 0·9223 | 190·1 | 98·5 | Nil. | 1·45 | |
+----------+---------+-------+--------+-------+-----------+--------+

The highest figures recorded for the iodine value of arachis oil are
101-105 (Oliveri), whereas the lowest values fall well within the
limits of those of olive oil.

Arachis oil is sometimes adulterated with cheaper oils, and notably
with sesame and cotton-seed oils. The determination of the analytical
values and the characteristic colour reactions will probably afford
information in such cases, while at the same time there would be a
decrease in the amount of arachidic acid that could be separated.

The methods of separating and determining this acid are described in
Chapter VIII. p. 108.

=Sesame Oil.=—This oil also goes by the name of _teel oil_ and
_gingelly oil_, and in commerce is sometimes described as _French salad
oil_.

It belongs to the same class of oils (_semi-drying_) as cotton-seed
oil, which it also resembles in its chemical composition.

It contains the glycerides of oleic, linolic, palmitic, and stearic
acid. The solid fatty acids amount to about 14 per cent. of the total
fatty acids, while, according to Farnsteiner, the linolic acid is about
12 per cent.

The unsaponifiable matter contains phytosterol, a body termed
_sesamin_, and a compound of the nature of a phenol, termed _sesamol_.
It is to the presence of this substance that the characteristic
furfural reaction (see Baudouin’s test, p. 105) is due.

This active constituent may be removed from sesame oil by treatment
with animal charcoal, and the oil may also be rendered inert by
prolonged heating over boiling water.

Sesame oil has a pale yellow colour and a pleasant odour of the grain.
It solidifies at a lower temperature (5° C.) than cotton-seed oil, and
does not yield the large proportion of “stearin” given by the latter.

In the elaidin test it gives a reddish-brown partially solid mass of
about the same consistency as the elaidin of cotton-seed oil.

Its iodine value (usually about 106) is somewhat lower than that of
cotton-seed oil, except in the case of the oil from Russian seed, which
has an iodine value of 114-115.

As is mentioned elsewhere, the addition of sesame oil to margarine
is compulsory in Germany, Austria, and Belgium, so that the product
possesses a “latent colour” which may be developed by the use of the
Baudouin reagent.

In addition to its use as a salad oil, and in pharmaceutical
preparations, sesame oil is employed as an adulterant of olive and
almond oils; while, in turn, it is liable to be adulterated with
arachis oil, cotton-seed oil, poppy oil, and rape oil.

The presence of the first may be detected by an estimation of the
arachidic acid (p. 108), while Halphen’s test will show the presence of
cotton-seed oil.

The other oils are detected by the general physical and chemical
characteristics, and, in the case of rape oil, by the characteristics
of its principal fatty acid, erucic acid.

=Cotton-Seed Oil.=—This oil, as has been already mentioned (p. 16),
is expressed in enormous quantities in the United States, while there
is a steadily increasing production in Egypt and India. In practice,
a ton of cotton seed yields about 2½ cwt. of crude oil, which is then
separated into “summer oil” and “foots” by refining (p. 23).

The bulk of the cotton-seed oil used for food in this country is
derived from Egyptian seed, for the Indian oil is considered to have an
unpleasant flavour.

Experiments made by Hooper, however, upon oils derived from American
seed grown in India (_Ann. Report, Indian Museum_, 1910, 26), show that
the fault lies with the method of screening the seed and the process of
refining the oil.

He finds that by treating Indian oils with the amount of alkali
corresponding to the acidity and giving a subsequent thorough washing
with water, the whole of the colouring matter, the so-called “bloom,”
and the acid taste are removed, and that the product has the light
colour and bland flavour of refined Egyptian oil.

Thus by removing all dirt from the seed and delivering the seed in
sound condition, and washing the oil to a sufficient extent after
the refining with alkali, there appears to be no reason why oils
from Indian seed should be in any respect inferior to Egyptian oils.
Hooper’s experiments also indicate that as much “stearin” could be
separated from Indian oils as from American or Egyptian oils.

Cotton-seed oil consists chiefly of the glycerides of oleic and
linolic acids, the latter, as is indicated by the iodine value, being
present in greater proportion than in olive oil, and amounting to
about 17 or 18 per cent. of the total fatty acids. The glycerides of
solid fatty acids which are present in solution, and separate out as
“cotton-stearin” on chilling the oil, consist principally of those
of palmitic acid with a small proportion of stearic acid (Hehner and
Mitchell).

Owing to the presence of the large amount of linolic acid, cotton-seed
oil belongs to the class of oils known as “semi-drying” oils, _i.e._
oils which thicken on exposure to the air, but, unlike the drying oils,
do not form a dry film until after the lapse of a long time.

When exposed to a temperature of about 10° to 14° C., cotton-seed oil
yields a deposit of the so-called “cotton-stearin” (_q.v._), while
the entire oil becomes solid at about the freezing-point of water.
The stearin, which is separated by filtration (p. 25), is a useful
by-product, which is utilised in the preparation of margarine. The
oil from which the “stearin” has been separated goes by the name of
“winter” cotton-seed oil.

Oils which have been refined by treatment with alkali and separation of
“stearin” have a mild taste and are practically devoid of free acids.
They are widely employed both as salad oils and as substitutes for lard
in cooking, but the bulk of the American oil is made up into margarine
or used in the manufacture of soap.

Cotton-seed oil is a common adulterant of olive oil, and, owing to
its forming a frequent ingredient of margarine, may find its way into
butter.

In addition to the colour reactions, described on p. 107, it may be
identified by the relatively high melting-point of its solid fatty
acids (32° to 38° C.), and by its iodine value (112-115).

In the elaidin test (p. 107) it yields a butter-like mass of an orange
colour, very different from the hard white elaidin produced by olive
oil.

Cotton-seed oil contains about 1 per cent. of unsaponifiable matter
consisting chiefly of phytosterol. The presence of cotton-seed oil in
animal oils and fats may thus be confirmed by the phytosteryl acetate
test (p. 101).

=Sunflower Oil.=—Enormous quantities of sunflower seeds are cultivated
in Russia for the production of an edible oil, and most of the oil
mills in that country are engaged in the industry.

The method of expression is similar to that used in this country for
linseed. The seeds are first “screened” from dirt, particles of stalk,
etc., and are then steamed and crushed to a paste, which is wrapped in
hair-cloths and expressed in a hydraulic press. Expression by hand is
still employed in some of the smaller mills.

When freshly obtained from clean seed, sunflower oil is a pale yellow
fluid with a pleasant odour and flavour, but the second (hot) pressings
are much darker in colour, and are used for illuminating purposes and
in the manufacture of varnish.

Sunflower oil has good drying properties, though these are less
pronounced than in the case of poppy or linseed oil. It consists of the
glycerides of oleic, linolic, and palmitic acids, and probably contains
a small amount of linolenic acid.

Its iodine value (about 130) is considerably higher than that of
cotton-seed oil.

When used as a salad oil it has the advantage of keeping fluid to a
very low temperature, but its drying capacity, which causes a film to
form upon the surface when exposed to the air, is a drawback from
which olive and similar non-drying oils are free.

Sunflower oil is occasionally employed as an adulterant of olive
oil. It would be detected by the increase in the iodine value, and,
according to Jean, by its having a slight reducing action upon silver
nitrate in Bechi’s test (_q.v._).

=Poppy Oil.=—The oil expressed from the seeds of the poppy (_Papaver
somniferum_), which is cultivated in Egypt and Asia Minor, has a mild,
bland taste, and is sometimes used as an edible oil.

Its chief use, however, is as a drying oil for paints, for which its
good drying capacity and its light colour make it particularly suitable.

It consists of the glycerides of oleic, linolic, and linolenic acids,
with a small proportion of those of solid fatty acids, including
stearic and palmitic acids.

It bears considerable resemblance to sunflower oil in its chemical and
physical characteristics, as is shown by the following typical values:—

+--------+----------------+--------+--------+----------------+
| | Saponification | Iodine | Hehner | Solidification |
|Sp. gr. | Value. | Value. | Value. | Point. |
+--------+----------------+--------+--------+----------------+
| 0·926 | 194 | 140 | 95·4 | -15° to |
| | | | | -20° C. |
+--------+----------------+--------+--------+----------------+

If added in any considerable quantity to olive oil there would be an
increase in the sp. gr. and iodine value of the latter.

=Maize Oil.=—This oil, which is also known as _corn oil_, is obtained
from the germs of the maize or Indian corn (_Zea mais_), and is used to
a limited extent as an edible oil.

It has a pale yellow colour, and a fragrant odour recalling that of the
fresh grain.

It resembles cotton-seed oil in its composition, and contains the
glycerides of oleic, linolic, and palmitic acids, together with an
appreciable quantity of those of volatile fatty acids, as is indicated
by its relatively high Reichert-Meissl value (4 to 4·5).

Like cotton-seed oil it belongs to the class of semi-drying oils,
slowly forming a dry skin when exposed to the air in a thin film.

The following values have been recorded:—

+--------+----------------+--------+--------+---------------+
| | Saponification | Iodine | Hehner | Melting-point |
|Sp. gr. | Value. | Value. | Value. | of |
| | | | | Fatty Acids. |
+--------+----------------+--------+--------+---------------+
| 0·9245 | 190 | 122 | 93·6 | 17°-20° C. |
+--------+----------------+--------+--------+---------------+

The presence of cotton-seed oil, which is sometimes used to adulterate
maize oil, would be shown by the characteristic colour reactions (p.
107). For the detection of maize oil in lard or in butter reliance
would have to be placed upon the general analytical values and upon the
results of the phytosteryl acetate test.

CHOCOLATE FATS

=Cacao Butter.=—In the manufacture of cocoa and chocolate a large
proportion of the fat contained in the cocoa-bean is expressed, and
forms a valuable by-product.

This fat, which is usually termed cacao butter, comes into the market
in moulded slabs, weighing several pounds each.

It is a hard substance of a yellowish colour, having an aroma of cocoa,
and, when broken, shows signs of crystalline structure.

Its flavour and high melting-point render it particularly suitable for
the “cream” of chocolate creams, and large quantities of it are used
for this purpose.

The chemical composition of cacao butter resembles that of other hard
fats, the differences being due to a different proportion of the
various glycerides.

It contains stearic, palmitic, lauric, and oleic acids, while
arachidic, and a fatty acid termed theobromic acid, are also said to
have been identified, though the presence of either is doubtful.

The hardness and high melting-point of the fat are due to the large
proportion (about 40 per cent.) of stearic acid it contains.

The melting-point of the commercial product ranges from about 27° to
34° C.

The relatively low iodine value (usually between 32 and 36) indicates
the presence of a much smaller amount of liquid fatty acids than of
solid fatty acids, the former, according to Farnsteiner, consisting of
oleic acid, and constituting 31 per cent. of the total fatty acids.

It has frequently been stated that cacao butter is not liable to become
rancid. This, however, is not the case, for the fat, like other fats,
does gradually decompose on exposure to light and air, though owing to
its consistency and the low proportion of glycerides of liquid fatty
acids present the process is not rapid, as in the case, for example, of
cocoanut oil.

Cacao butter is frequently adulterated, the principal substances liable
to be found being stearic acid, cocoanut oil, paraffin wax, beeswax,
and various vegetable oils.

Cacao butter fetches too high a price to be used in the lowest grade of
chocolate creams, and various substitutes are now sold.

=Cocoanut and Palm-Kernel Oil Stearins.=—Among the most common of
these cheaper products are the “stearins,” obtained by expression
from cocoanut oil and palm-kernel oil, both of which in their original
condition are too soft, and melt at too low a temperature to be
suitable for this purpose.

In preparing more solid fats these oils are melted and refined, then
chilled down, and subjected to pressure in the cold in a hydraulic
press. A fractionation is thus effected, the expressed portion, known
as cocoanut or palm-nut olein, being much more fluid than the stearin
left in the press, while the latter is more consistent than the
original fat.

Thus while the melting-point of cocoanut oil is usually about 23° C.,
that of the separate is about 30° C.

The following results were obtained by Sachs (_Chem. Rev. Fett- u.
Harz.-Ind._, 1908, xv. 30) in the examination of commercial samples of
these stearins:—

LEGEND:
(A) = Saponification Value.
(B) = Reichert-Meissl Value.
(C) = Melting-point of Fatty Acids.
+----------------+--------------+-------+---+-----+------+---------+
| | |Sp. gr.| | | | |
| |Melting-point,| at |(A)| (B) |Iodine| (C) |
| | °C. |100° C.| | |Value.| |
+----------------+--------------+-------+---+-----+------+---------+
|Hard cocoanut | | | | | | |
| stearin |29·3 to 29·5 |0·8700 |252| 3·4 |4·0 to| 28·1 |
| | | | | | 4·5 | |
|Palm-nut stearin|31·5 to 32 |0·8700 |242| 2·2 | 8 |28·5-29·5|
+----------------+--------------+-------+---+-----+------+---------+

Frequently these products are rendered still more consistent by the
addition of a small proportion of an animal stearin or some vegetable
fat of higher melting-point, such as Japan wax.

Thus a commercial preparation consisting of a mixture of cocoanut
stearin with 25 per cent. of Japan wax, melted at 34° to 35°·5 C.,
or approximately at the same temperature as a good specimen of cacao
butter.

=Other Vegetable Fats.=—Of late years various exotic vegetable fats
have been put upon the market as chocolate fats either in their pure
state or in admixture with cocoanut or palm-nut stearins. These fats
include dika fat, tankawang fat (Borneo tallow) and Illipé fat.

_Dika fat_, which is obtained from the seed kernels of _Mangifera
gabonensis_ and other members of the same family, growing on the West
Coast of Africa, is a hard fat, melting at about 39° C. (or higher than
cacao butter), and having an iodine value (5) about the same as that of
cocoanut oil.

_Borneo tallow_ (_tankawang fat_) derived from the seed kernels of
_Shorea aptera_ and other members of the _Dipterocarpi_. The native
method of separating the fat is to suspend the kernels in baskets above
boiling water, and when soft, to express them in primitive presses.
According to Sachs (_loc. cit._), Borneo tallow melts at 37°·5 C., and
has an iodine value of 30-31.

_Illipé butter_ (_Mahua butter_), which is derived from the seeds of
_Bassia latifolia_, is a yellow fat, large quantities of which are
eaten in India.

Nine samples of the Indian product examined by Crossley and Le Sueur
had melting-points ranging from 23° to 29° C., and iodine values of
58·4 to 67·8. The relatively low melting-point appears to depend upon
the large proportion of glycerides of liquid fatty acids present, and
this fat would probably yield a hard stearin on expression.

Other fats that might be used for this purpose, if they could be
obtained in sufficient quantity, are shea butter, from the seeds of
_Bassia Parkii_ (melting at about 25° C.); Mafura tallow, melting at
35° to 42° C.; Mkani fat, melting at about 40° C.; and Malabar or Piney
tallow, produced by the East Indian tree, _Vateria indica_ (melting at
about 37° C.).

Sachs (_loc. cit._) states that favourite substitutes for cacao butter
consist of a mixture of two-thirds of palm-nut stearin with one-third
of cocoanut stearin, and of a mixture of 40 per cent. of Borneo tallow
with 60 per cent. of cocoanut stearin.

CHAPTER VIII

ANALYSIS OF RAW MATERIALS AND FINISHED PRODUCTS

General Methods of Analysis of Fats and Oils—Special
Tests for Individual Oils—Analysis of Butter,
Margarine, Lard, Cheese, Chocolate.

The adulteration of fats and oils becomes year by year more scientific,
the latest developments of chemical research being prostituted to the
purpose of enabling sophisticated articles to elude the vigilance of
the public analyst, whose duty it is to detect such adulteration. A
striking instance of this is furnished by the methods of adulterating
butter described in Chapter IV.

As was there mentioned, a method for the examination of pure butter,
formulated by Reichert in 1879 and subsequently slightly modified by
Meissl and Wollny, was based on the presence of volatile fatty acids,
such as butyric acid, in butter. Butter substitutes, as usually made,
do not contain these volatile fatty acids, at any rate in appreciable
quantity, except when cocoanut oil has been added, and this, therefore,
afforded a means of detecting the presence of artificial in genuine
butter. It has been found, however, that some manufacturers of butter
substitutes, especially on the Continent, have actually added these
volatile fatty acids, ostensibly to improve their flavour, but there
can be little doubt with the real object of enabling the artificial
product to be sold as genuine butter.

It is unfortunately the case that the unscrupulous manufacturer is
generally slightly in advance of the examining authority, and as fast
as the latter detects one form of adulteration, and devises means for
its ready determination, some new form of fraud is invented to take its
place.

As a result of this competition between expert adulterator and public
analyst, the methods for the examination of edible fats are constantly
being improved and increased, and some extremely fantastic and
far-fetched tests have been suggested. In the following pages, however,
only those most usually adopted in a works’ or commercial laboratory
are described.

GENERAL METHODS OF EXAMINATION OF FATS AND OILS

=Raw Materials.=—The appearance, colour, and odour of the sample should
be observed, and any characteristic feature recorded. The taste is
also frequently of value in judging the purity of a fat or oil, but
deductions from this can only be made after considerable experience.

The following physical and chemical data may be determined:—

=Specific Gravity.=—In the case of oils liquid at ordinary
temperatures, this is usually taken at 15° C., the weight of a given
volume of the oil being compared with that of the same volume of water,
at 15° C., the symbol used to denote this being

15°
“_d_ ———— ”.
15°

If a sufficient quantity of the oil is available a Westphal balance or
a hydrometer may be employed for the purpose; if only a small quantity
can be obtained, a specific gravity bottle or Sprengel or Nicol
pycnometer should be used. This latter method is to be preferred where
great accuracy is desirable. The specific gravity bottle or pycnometer
must be first calibrated by filling it up to the mark with distilled
water at 15° C., and weighing it.

The specific gravity of solid fats is taken at some higher temperature
at which they are fluid, preferably at the temperature of a boiling
water-bath, which will generally be found to be about 99° C. This is
compared with the weight of a similar volume of water at 15° C., and is
represented by

99°
“_d_ ———— ”.
15°

The specific gravity of oils and fats is liable to increase with age,
and also varies with the method of treatment during refining.

The specific gravity of butter fat is best taken at a temperature of
35° C., for reasons which are dealt with under the heading of “Butter,”
in Chapter IV.

=Free Fatty Acids.=—These are determined by warming on the water-bath
for a few minutes a weighed quantity (2 to 10 grms. according to the
degree of acidity of the fat) of the fat or oil, with 25 c.c. of
purified methylated alcohol, which has been neutralised immediately
prior to use, with N/10 potassium hydroxide solution, and after adding
phenol-phthalein solution, slowly running in from a burette N/2 or
N/10 alcoholic potassium hydroxide solution until a faint permanent
pink colour is produced. Each c.c. of N/2 or N/10 alkali corresponds
to 0·141 or 0·0282 grm. respectively of free fatty acids, expressed as
oleic acid, and from this the percentage of acidity is calculated.

The free acidity is frequently expressed as the _acid value_, which
represents the number of milligrams of potassium hydroxide, KOH,
required to neutralise the acidity in 1 grm. of oil or fat.

_Example._—If 6·656 grms. fat required 1·5 c.c. N/10 alcoholic
potassium hydroxide solution to neutralise it, then

1·5 × 0·0282 × 100
—————————————————— = 0·63 per cent.
6·656

free fatty acids, expressed as oleic acid.

The _acid value_ in this case would be

1·5 × 0·00561 x 1000
———————————————————— = 1·26.
6·656

The maximum permissible limit for free acidity depends on the nature of
the fat or oil. For edible tallows it should not exceed 3 per cent.,
for lard 0·5 per cent., and for cocoanut oil 2 per cent.

=Saponification Value.=—It has been shown in Chapter I, how the various
glycerides contained in fats and oils are split up or saponified by
the action of caustic alkalies, one molecule of a triglyceride such
as stearin requiring three molecules of potassium hydroxide for its
saponification (cf. p. 4).

The composition of the various fats and oils being fairly constant, the
amount of alkali required for the saponification of any given weight is
also nearly constant. Koettstorfer first utilised this fact in 1879 for
the analysis of butter fat, and it has now become the basis of one of
the most important factors in the analysis of nearly all fats and oils,
the amount of any fat which is saponified by 1 grm.-molecule or 56·1
grms. of caustic potash being termed its _saponification equivalent_.

The more usual method of expressing the same thing is the number of
milligrams of potassium hydroxide required to saponify 1 grm. of fat,
which is called the _saponification value_. The difference between the
saponification and acid values is spoken of as the _ester value_.

To convert saponification equivalent into saponification value, it is
merely necessary to divide 56·1 by the saponification equivalent, and
multiply the quotient by 100.

To determine the saponification value, about 2 grms. of the fat or
oil are weighed out into a conical flask of about 200 c.c. capacity,
25 c.c. of _neutral_ methylated spirit added, and 25 c.c. of an
approximately N/2 alcoholic solution of potassium hydroxide run in
from a burette, similar quantities of methylated spirit and alcoholic
potassium hydroxide solution being also placed in another flask to
serve as a blank test. The two flasks are now fitted with reflux
condensers (which may be simply glass tubes, about four feet long and
half an inch in diameter, inserted through a cork), and are placed on a
steam or water-bath. The contents are then boiled until saponification
of the fat is complete, which may take from thirty to sixty minutes,
and is known to be accomplished when all globules of oil disappear. A
few drops of phenol-phthalein solution are now added to each flask,
and N/2 hydrochloric or sulphuric acid carefully run in from a burette
until the pink colour is discharged. The difference in the amount of
acid required by the two flasks indicates the quantity of potassium
hydroxide required to saponify the weight of fat or oil taken.

_Example._—2·1314 grms. fat required 10·7 c.c. N/2 hydrochloric acid to
neutralise unabsorbed alkali.

In the blank test 25 c.c. of approximately N/2 alcoholic potassium
hydroxide solution required 25·6 c.c. of N/2 hydrochloric acid to
neutralise it.

N
25·6 - 10·7 = 14·9 c.c. ————
2

alcoholic potassium hydroxide solution required to saponify the fat, and

2·1314 × 1000 × 2
————————————————— = 286·1
14·9

saponification equivalent, and

56·1 × 100
———————————— = 196·1,
286·1

the saponification value.

If the quantity of fat or oil employed for the estimation of acidity is
only about 2 grms., the saponification value may also be determined on
the same quantity. After proceeding as described above for the acidity
estimation, 25 c.c. of approximately N/2 alcoholic potassium hydroxide
solution are added to this, and the process continued as described
above.

=Iodine Absorption.=—This test, devised by Hübl in 1884, and
subsequently modified by Wijs, by Hanus, and by Waller, is based upon
the capacity of unsaturated fatty compounds to absorb iodine, with
formation of addition compounds. The amount of iodine absorbed is
therefore a measure of the unsaturated compounds present in a fat, and
is very fairly constant for any given fat in the fresh condition. The
action of Hübl’s solution is attributed by Ephraim to the presence
of iodine monochloride, but by Wijs to that of hypoiodous acid. The
percentage of iodine absorbed is usually recorded as the _iodine
number_ or _iodine value_.

In Hübl’s method, two solutions are required—(1) containing 25 grms.
iodine in 500 c.c. of absolute alcohol, and (2) containing 30 grms.
mercuric chloride in 500 c.c. of absolute alcohol. These solutions
should be kept separate, and only mixed about twelve to twenty-four
hours before use.

The process is carried out as follows:—Into a tightly fitting stoppered
bottle is introduced 0·2 to 0·6 grm. of the fat, 10 c.c. chloroform
added, and 25 c.c. of the mixed Hübl solution run in from a burette.
The bottle is then firmly stoppered, and allowed to stand in a dark
place for four hours, a similar bottle containing the same quantities
of chloroform and Hübl solution being placed by its side as a blank
experiment.

At the end of four hours, 20 c.c. of a freshly prepared 10 per cent.
potassium iodide solution and 150 c.c. of water are added to each
bottle, and the excess of iodine titrated with recently standardised
N/10 sodium thiosulphate solution, the bottles being vigorously shaken
during the titration, and fresh starch solution used for determining
the final point. The difference in the number of c.c. of N/10 sodium
thiosulphate solution required by the contents of the two bottles is
a measure of the iodine absorbed by the fat. This figure, multiplied
by the iodine equivalent of the sodium thiosulphate solution (found by
titrating it with a known weight of pure resublimed iodine), and by
100, and divided by the weight of fat taken, gives the iodine value of
the fat.

_Example._—0·539 grm. oil taken. Blank bottle, with iodine solution
and chloroform only, required 61·4 c.c. N/10 thiosulphate; bottle
containing oil required 25 c.c. N/10 thiosulphate. The iodine
equivalent of the thiosulphate solution was found to be 1 c.c. = 0·0126
grm. I.

61·4 - 25·0 × ·0126 × 100
Then ——————————————————————————— = 85.1 iodine value.
·539

_Wijs’ Method._—The Hübl method has now to a very large extent been
displaced by the Wijs process, in which the iodine is absorbed by
the fat much more quickly, only about thirty minutes’ contact being
required. The Wijs iodine reagent consists of a solution of iodine
monochloride in glacial acetic acid, and may be prepared by either
weighing out 7·9 grms. of iodine trichloride (which must be done in a
weighing bottle), and 8·7 grms. of iodine, dissolving these separately
in glacial acetic acid, mixing and making up to a litre with glacial
acetic acid, or by dissolving 13 grms. of iodine in a litre of
glacial acetic acid, and passing chlorine into the solution until the
iodine is all converted into the iodine monochloride—a point which
may be determined by the gain in weight, or, with a little practice,
by the change in colour of the solution. The details of the process
are exactly similar to those in the Hübl method, except that it is
preferable to dissolve the fat in carbon tetrachloride instead of in
chloroform.

=Bromine Absorption.=—This is similar in principle to the iodine
absorption, and though numerous processes, both gravimetric and
volumetric, have been proposed for its determination, it has now been
almost entirely superseded by determination of the iodine absorption.
A process devised by McIlhiney (_J. Amer. Chem. Soc._, 1894, 295, and
1899, 1084), however, deserves attention, for it estimates both the
added and the substituted bromine.

The weighed quantity, say 0.5 grms. of the oil or fat, is weighed
out, and dissolved in 10 c.c. of chloroform, and 20 c.c. N/3 solution
of bromine in chloroform added. After two or three minutes 20 to 30
c.c. of a 10 per cent. potassium iodide solution are added, and the
liberated iodine titrated with standard N/10 thiosulphate, the result
giving the bromine forming addition compounds. After this, 5 c.c. of
neutral 2 per cent. potassium iodate solution are introduced, and the
liberated iodine titrated, the result in this case corresponding to the
hydrobromic acid formed by the bromine in producing substituted bodies,
or, in other words, giving the _bromine substitution value_.

=Titre, or Solidifying Point of the Fatty Acids.=—Many methods for
determining the melting and solidifying points of fatty matters have
been proposed, but the _titre test_, due to Dalican, is that which
is now most generally adopted. This consists in determining the
solidifying point of the fatty acids separated from a fat or oil, a
figure which is an important characteristic of most fats, and in the
case of tallows is largely employed as the basis for their commercial
valuation. It is, of course, essential that in the preparation of
artificial butters from a standard formula the firmness of the fats
used should be as nearly as possible constant, and this is best
determined by the titre test.

The test is carried out by first saponifying the fat with alcoholic
sodium hydroxide solution, decomposing the resulting soap with dilute
sulphuric acid, and after washing and drying the liberated fatty
acids, determining their solidifying point. One ounce of the sample
is melted in a shallow porcelain basin on a water-bath, and 30 c.c.
of a 25 per cent. solution of sodium hydroxide added, together with
50 c.c. of redistilled methylated spirit. The contents of the basin
are now evaporated on the water-bath, with constant stirring, until
a pasty mass of soap is formed, and this is redissolved in a further
50 c.c. of redistilled methylated spirit, and again evaporated to
dryness on the water-bath. The solid soap thus obtained is dissolved
in water, sufficient dilute sulphuric acid added to decompose it, and
the whole warmed until the fatty acids melt to a clear oily liquid on
the surface. The water underneath is now siphoned off, more distilled
water added to wash out any remaining trace of mineral acid, and again
siphoned off, this treatment being repeated until the washings are no
longer acid to litmus paper. The melted fatty acids are next poured
on to a dry filter paper, which is inserted in a funnel resting on a
beaker, and the latter is placed either in the water-bath or in an
air-oven at about 100° C. until the clear fatty acids have filtered
through it.

From 10 to 15 grms. of these dry fatty acids are transferred to a wide
test tube, about six inches long and one inch in diameter, which is
inserted through a cork into a flask or wide-mouthed bottle, to protect
the tube from draught. The tube is closed with a loosely fitting
perforated cork, through which passes a short range thermometer (0°
to 60°), accurately graduated in fifths of a degree centigrade, and
having its bulb just immersed in the fatty acids as near the centre as
possible.

The temperature is now raised to a few degrees above the melting-point
of the fatty acids, and allowed to cool down without stirring. As
soon as the fatty acids just begin slowly to solidify, they are
stirred round gently with the thermometer, the temperature on which
will gradually fall till a minimum point is reached. Stirring is now
discontinued, and the rise in temperature, which is usually produced
by the heat given out by the acids in crystallising, is observed. The
maximum temperature attained by the fatty acids during this rise is the
“titre” of the sample.

=Refractive Index.=—The determination of the refractive power of a fat
or oil, or of its fatty acids, is frequently very useful in judging the
purity of a sample, or in drawing conclusions as to the composition of
a mixture of fats.

The refractive index itself may be either directly determined by means
of an Abbé total reflection refractometer, or an Amagat and Jean
oleo-refractometer (_Analyst_, 1890, 87), or, as is more usual in the
case of butter, the refractive power may be read off on an arbitrary
scale by means of a Zeiss butyro-refractometer.

One of the great advantages of this test is the ease and rapidity with
which a number of samples may be examined, while a further advantage of
the Abbé and Zeiss instruments is that only a very small quantity of
the sample—5 or 6 drops—is necessary.

The different forms of apparatus are fully illustrated and described in
the catalogues of most firms supplying chemical apparatus, and it is
therefore unnecessary to give a description here.

Different observers employ various temperatures for determining
refractive indices, but that most usual for oils and fats, with the
exception of butter, is 60° C. The best temperature of observation for
butter is 40° C.

=Unsaponifiable Matter.=—The unsaponifiable matter present in the
ordinary animal and vegetable fats is very small in amount, and the
addition of any paraffin or other hydrocarbon is therefore readily
detected by estimating the unsaponifiable matter. The usual method is
to saponify about 5 grms. of the fat, dissolve the soap in water, and
extract the unsaponified fatty matter with ether. The saponification is
effected by boiling the fat with 50 c.c. of approximately N/2 alcoholic
potassium hydroxide solution under a reflux condenser, with frequent
agitation, for about an hour. The soapy solution is then evaporated to
dryness in a porcelain basin on a steam or water-bath, and the soap
obtained is dissolved in about 200 c.c. of hot water and transferred,
as soon as sufficiently cool, to a 10 oz. separating funnel. To this
is now added 50 c.c. ether, and the whole well shaken, and allowed
to separate. The aqueous soap solution at the bottom is now run into
another similar separator, and the ethereal extract washed with water
to remove any soap dissolved therein. The washings are added to the
aqueous soap solution, which is again extracted with a second 50 c.c.
of ether, separated, the ethereal extract washed with water, and the
extraction repeated a third time. The three washed ethereal extracts
are then transferred to a tared flask, the ether distilled off in a
water-bath, and the residue dried in the oven at 100° C. till constant
in weight. This residue is the unsaponifiable matter in the weight of
fat taken, whence the percentage may be calculated.

Difficulty often occurs during this process through the formation of
an emulsion between the ethereal and the aqueous solutions, which
prevents a sharp separation of the two layers. To overcome this,
various expedients are recommended, such as the addition of a few c.c.
of alcohol or glycerin or of more ether or water, careful warming, or
gentle rotation.

The unsaponifiable matter may consist of cholesterol, a constituent of
many animal fats, of phytosterol, a substance similar to cholesterol
found in vegetable fats, of solid alcohols, such as cetyl and ceryl
alcohols, present in spermaceti and Chinese wax, or of hydrocarbons,
which do not occur naturally in either animal or vegetable fats, but
are occasionally added as adulterants.

To examine the unsaponifiable matter for cholesterol and phytosterol
a small quantity is dissolved in acetic anhydride, and one drop of
the solution added to one drop of 50 per cent. sulphuric acid on a
white porcelain tile, when, if either is present, a blood red to
violet coloration is produced. They may be distinguished from each
other by their crystalline form, cholesterol crystallising in laminæ,
phytosterol in needle-shaped tufts; or by the melting-points of their
acetates, cholesteryl acetate melting at 114°·3-114°·8, and phytosteryl
acetate at 125°·6-137° C.

The fact that the unsaponifiable matter of animal fats contains
cholesterol, while that of vegetable oils and fats contains
phytosterol, has been made the basis of a test for detecting the
presence of vegetable oils and fats in butter or lard. This test,
which was first proposed by Bömer (_Zeit. Untersuch. Nahr. Genussm._,
1898, 81), consists in saponifying the fat with alcoholic potash,
and extracting the unsaponifiable matter with ether, which is then
distilled off, and the residue recrystallised from alcohol. The
process has been subsequently improved by converting the cholesterol
or phytosterol into the acetic esters by heating it with acetic
anhydride, and determining the melting-point of the resulting ester.
As mentioned above, that of cholesterol melts at about 114° C., that
of phytosterol at 125°·6-137° C., and, according to Bömer, an acetate
melting at 117°-118° C. corresponds to an addition of 1 to 2 per cent.
of vegetable oil; at 120°-121° C., to an addition of 2 to 3 per cent.
of vegetable oil; and at 123°-125° C., to an addition of 3 to 4 per
cent. of vegetable oil.

The following method for carrying out this test, which is known as the
_phytosteryl acetate test_, is described by Revis and Bolton (Allen’s
_Commercial Organic Analysis_, ii. p. 301).

Fifty grms. of the clear fat are boiled with 75 c.c. of 95 per cent,
alcohol, cooled, and the alcohol poured off, a second extraction being
made with a further 75 c.c. of alcohol. These combined extracts, which
will contain the greater part of the cholesterol and phytosterol
and some fat, are transferred to a porcelain basin, and an excess
of solid sodium hydroxide added, the mixture being then evaporated,
with gentle stirring. After most of the alcohol has evaporated, more
than sufficient sodium bicarbonate is added to convert the excess of
sodium hydroxide into sodium carbonate, then some sand, and the whole
evaporated to dryness, ground up in the dish, and extracted with light
petroleum spirit. The residue from the ether is heated with 5 c.c. of
(approximately) N/2 alcoholic sodium hydroxide solution, and again
evaporated to dryness, with sand. A fresh extraction with petroleum
spirit is made, followed by evaporation, and the residue is taken up
with the smallest possible quantity of absolute alcohol. If necessary,
the solution is boiled with animal charcoal and some 95 per cent.
alcohol, filtered and evaporated to dryness. The crystals obtained are
examined microscopically, then converted into their acetate by boiling
with acetic anhydride in a covered watch-glass, evaporating off the
excess of acetic anhydride on the water-bath, and recrystallising them
from absolute alcohol.

Further tests for cholesterol have also been published by Lifschutz
(_Ber. Deut. Chem. Ges._, 1908, 252-5) and Golodetz (_Chem. Zeit._,
1908, 160).

The method of the former depends on the oxidation of cholesterol
to oxycholesterol ester and oxycholesterol. A few mgrms. of the
unsaponifiable matter are dissolved in 2 to 3 c.c. of glacial acetic
acid, a little benzoyl peroxide added, and the solution boiled, after
which four drops of strong sulphuric acid are added. If cholesterol is
present, a violet-blue or green colour is produced, the violet colour
being due to oxycholesterol ester, the green to oxycholesterol.

Golodetz has devised two tests:—(1) the addition to a small quantity of
the unsaponifiable matter of one or two drops of a mixture of 5 parts
of concentrated sulphuric acid with 3 parts of formaldehyde solution,
this reagent turning cholesterol a blackish-brown colour; and (2)
the addition of one drop of 30 per cent. formaldehyde solution to a
solution of the unsaponifiable matter in trichloracetic acid, when, if
cholesterol is present, an intense blue coloration is produced.

Of the less frequently used methods of examination the following may be
mentioned:—

=Valenta’s Acetic Acid Test=, which depends on the solubility of
most oils and fats in hot glacial acetic acid of 1·0562 sp. gr., the
temperature at which a warmed mixture of 3 c.c. melted fat and 3 c.c.
acetic acid becomes turbid on cooling being noted.

The test has been slightly modified by Pearmain and Moor, who use a
short stoppered tube, into which is weighed 2·75 grms. of the fat or
oil, followed by 3 c.c. of acetic acid. The tube is then stoppered and
heated in a water-bath, the temperature being raised until the contents
of the tube become clear on shaking, after which the source of heat is
removed, and the tube allowed to cool down gradually in the centre of
the water-bath until the contents again become slightly turbid. The
temperature at which this takes place is recorded, and is a fairly
definite figure for any given oil. This test is of some value in the
examination of butter for margarine, as is pointed out in Chapter IV.
p. 48; the temperature at which the solution of the latter in acetic
acid becomes turbid being very much higher than that of the former.

The following are the figures obtained by Pearmain and Moor by the
above method:—

° C.
Butter fat 23-38
Margarine 94-97
Lard 97-99
Tallow 96-99
Cotton-seed oil 71-89
Sesame oil 90-97
Olive oil 83-91

The drawback of this test is that slight variations in the strength of
the acetic acid, such as inevitably result from opening the bottle,
cause considerable variations in the temperatures of turbidity. To
obviate this it is advisable to compare the results with those given by
specimens of butter fat of known purity.

=Maumené’s Test=, first proposed in 1852, consists in observing the
rise of temperature which takes place when the fat or oil is mixed with
concentrated sulphuric acid. Various methods of applying the test have
been proposed by different authorities, that suggested by Archbutt
(Allen’s _Commercial Organic Analysis_) being as follows:—Fifty grms.
of oil are weighed into a 200 c.c. beaker, and the latter immersed
in a capacious vessel of water, together with the bottle of strong
sulphuric acid, until they are both at the same temperature, which
should not be far from 20° C. The beaker containing the oil is then
wiped, and placed in a cotton-wool nest previously made for it in a
cardboard drum, or a wider beaker. The immersed thermometer is then
observed, and the temperature recorded. Ten c.c. of the concentrated
sulphuric acid should then be withdrawn from the bottle with a pipette,
and allowed to run into the oil. During the addition of the acid, which
should occupy about one minute, the mixture must be constantly stirred
with the thermometer, and the agitation continued till no further
rise of temperature ensues. This point is readily observed, as the
mercury remains constant for a minute or two, and then begins to fall.
Very different results are obtained according to the strength of acid
employed, the best strength being 97 per cent.

Thomson and Ballantyne (_Journ. Soc. Chem. Ind._, 1891, x. 233)
proposed to determine the “_specific temperature reaction_” of the oil,
this being obtained by noting (1) the rise of temperature produced
when 50 grms. of water are mixed with 10 c.c. of strong sulphuric acid
in the same vessel and under the same conditions as those to be used
for mixing the acid and oil; (2) mixing the oil and acid as described
above, and then multiplying the rise in temperature produced by the
oil-acid mixture by 100, and dividing by the rise in temperature given
by the water-acid mixture. The following figures are given by Thomson
and Ballantyne:—

Temperature.
Oil. Water = 100° C.
Olive 89-95°
Arachis 105-137°
Cotton-seed 163-170°

It has been shown by one of the authors (M.) (_Analyst_, 1901, xxvi.
169), that if the oil be dissolved in an inert solvent, such as
carbon tetrachloride, the rise in temperature on adding sulphuric
acid is usually proportional to the iodine value, i.e. the degree of
unsaturation of the oil.

=Bromine Thermal Value.=—The heat reaction with bromine has been
recommended as a rapid means of ascertaining the degree of unsaturation
of oils and fats by Hehner and Mitchell (_Analyst_, 1895, xx. 146),
a weighed quantity of the sample being dissolved in chloroform or
acetic acid, and the rise in temperature on addition of bromine noted.
The oil, chloroform, and bromine having first been brought to the
same temperature, 1 grm. of oil is dissolved in 10 c.c. chloroform
in a Dewar’s vacuum-jacketed test tube, and 1 c.c. of bromine added
from a special pipette. This consists of a 1 c.c. pipette with a
narrow tube, bent twice at right angles, connected to its top, the
horizontal portion of the tube containing caustic lime kept in position
by asbestos plugs. The mixture is immediately stirred, and the rise
in temperature measured with a thermometer graduated in fifths of a
degree. In the case of most ordinary oils and fats a relationship is
shown to exist between the rise in temperature and the iodine value,
so that this ratio having once been ascertained for the apparatus
employed, the iodine value may be readily calculated from the rise in
temperature observed on adding the bromine.

The preceding methods of examination are more or less generally
applicable to all edible fats and oils, but there are numerous special
tests applicable only to individual oils, of which the following are
the most important. The application of these is also discussed more
generally in the sections dealing with the special oils.

SESAME OIL

_Baudouin’s Test._—This is carried out by dissolving 0·1 grm. of cane
sugar in 10 c.c. hydrochloric acid of sp. gr. 1·2, and adding this to
20 c.c. of the oil under examination, shaking the mixture thoroughly
and allowing it to stand. The presence of as little as 2 per cent. of
sesame oil imparts a crimson red colour to the aqueous liquid. This
reaction is given by even the most rancid oils, though the colour
produced is less intense.

A modification of this, consisting in adding 0·1 c.c. of a 2 per cent.
alcoholic solution of furfural to the hydrochloric acid instead of
the 0·1 grm. sugar, was devised by Villavecchia and Fabris, who found
the reaction to depend upon the formation of furfural; while Wauters
suggested that instead of mixing the reagent with the oil, the latter
should be poured upon the reagent, under which conditions less than 1
per cent. will impart a crimson colour to the surface of contact.

Sprinkmeyer and Wagner (_Zeit. Nahr. Genussm._ 1905, x. 347-353) have
still further increased the delicacy of the test, so that as little
as 0·1 per cent. of sesame oil may be detected. In their process
about 100 grms. of the filtered fat are twice extracted with 20 to 30
c.c. of glacial acetic acid at 60° C. The acid extracts are separated
and evaporated, and the residue tested as described above. In the
case of butter containing colouring matter, which may interfere with
the reaction, the latter may be removed by evaporating the acetic
acid residue with 10 c.c. of alcohol and 5 c.c. of saturated barium
hydroxide solution, and extracting the residue several times with light
petroleum spirit, which is then evaporated, and the final residue
treated with the furfural solution.

_Tocher’s Test._—A freshly made solution of 1 grm. of pyrogallol in 15
c.c. of concentrated hydrochloric acid is shaken up in a separating
funnel with 15 c.c. of the oil, and allowed to separate. The aqueous
liquid is then drawn off, filtered, and boiled for about five minutes,
when, if sesame oil is present, it appears red by transmitted and blue
by reflected light.

OLIVE OIL

An important test for the purity of this oil is based on the elaidin
reaction (p. 11), the degree of hardness of the product obtained by
treatment of the oil with nitrous acid and the time required for its
solidification being observed.

The best method of applying the test is to make use of the action
of nitric acid on mercury, a reagent being prepared by dissolving 1
c.c. of mercury in 12 c.c. of cold nitric acid of 142 sp. gr. When
this is shaken with the oil in a wide-mouthed stoppered bottle in the
proportion of 2 c.c. of reagent to 50 c.c. of oil, the shaking being
repeated at intervals of ten minutes for two hours, and the temperature
being kept constant at not less than 25° C., a bright lemon-yellow
coloured solid mass is obtained with olive oil. The products of the
reaction with almond, lard, sperm, and arachis oils are also solid, but
those yielded by rape, sesame, cotton-seed, sunflower, cod-liver, and
porpoise oils have a consistency resembling that of butter, while those
from linseed and other drying oils are liquid.

COTTON-SEED OIL

There are two well-known tests for this oil, those of Bechi and
Halphen, both of which have undergone various modifications.

Bechi’s, or the silver nitrate test, requires the preparation of two
solutions: (1) containing 1 grm. of silver nitrate dissolved in 200
c.c. or alcohol (98 per cent. by volume), to which is added 40 c.c. of
ether and 0.1 grm. of nitric acid; and (2) a mixture of 15 c.c. of rape
oil with 100 c.c. of amyl alcohol. Ten c.c. of the oil to be tested
are mixed in a test tube with 1 c.c. of solution (1), and then shaken
with 10 c.c. of solution (2). The mixture is now divided into two equal
parts, and one-half immersed in boiling water for fifteen minutes,
after which it is withdrawn and compared with the unheated portion. In
the presence of cotton-seed oil a reddish-brown coloration is developed.

_Halphen’s Test._—Equal parts of the oil or fat (or its fatty acids),
amyl alcohol, and a 1 per cent. solution of sulphur in carbon
bisulphide, are heated together in a test tube placed in a boiling
water bath until effervescence ceases, and then transferred to a
boiling brine-bath for about an hour, when, if cotton-seed oil is
present, a pink coloration is produced. The reaction may be rendered
much more rapid, according to Rupp (_Zeit. Untersuch. Nahr. Genussm._,
1907, xiii., 74), by heating the mixture in a stoppered flask.

The production of a coloration with Bechi’s or Halphen’s reagent does
not invariably prove the presence of cotton-seed oil, as the pure fat
of animals fed with cotton-seed cake, even some long time previously,
has been found to give the reaction. On the other hand, failure to
obtain a reaction does not prove the absence of cotton-seed oil, since
heating the oil to 250° C. causes it to give negative results in these
tests.

ARACHIS OIL

The great similarity in the properties of this oil and olive oil
renders some means of distinguishing one from the other necessary,
and a process for the purpose has been based on the different
chemical composition of the fatty acids, the arachis oil containing a
considerable proportion of arachidic and lignoceric acid.

This arachidic acid (the term also being used to include the lignoceric
acid) may be determined by the following process due to Renard and
modified by Lewkowitsch:—About 10 grms. of the oil are saponified
with alkali, as described under the “titre test,” the soap dissolved
in water, excess of alkali neutralised with acetic acid, and the lead
salts of the fatty acids precipitated by addition of a solution of lead
acetate, filtered off, and extracted with ether, all but the palmitate
and arachidate being dissolved. These latter are decomposed with
hydrochloric acid, the fatty acids separated from lead chloride, and
dissolved in 50 c.c. of hot 90 per cent. alcohol.

On cooling this solution, arachidic acid will crystallise out if
arachis oil is present, and the amount of arachidic acid may be
estimated, if desired, by filtering it off, and washing it twice with
10 c.c. of 90 per cent. alcohol, and once with alcohol of 0.890 sp.
gr. The residue on the filter is now extracted with boiling absolute
alcohol in which arachidic acid is soluble, the solution evaporated to
dryness, and the arachidic acid weighed.

This amount has to be corrected by the addition of 0·0025 grm. for each
10 c.c. of 90 per cent. alcohol used in the crystallisation and washing
if the treatment has been carried out at 15° C., or 0·0045 for 10 c.c.
if it was done at 20° C. Arachis oil contains about 5 per cent. of
arachidic acid, so that twenty times the total amount of arachidic acid
represents the quantity of arachis oil in the sample under examination.
The melting-point of arachidic acid is 71°-72° C.

BUTTER

An analysis of butter for the purpose of the Food and Drugs Act should
comprise determination of the water and examination of the fatty
matter, together with tests for colouring matter and preservatives. In
addition, estimations of the casein, ash, and salt are also sometimes
made.

The effect of heating a little of the sample in a spoon is a useful
rough indication of its purity. Pure butter produces considerable foam,
and turns brown, but butter substitutes do not foam appreciably, and
unless specially prepared to do so (see Chapter IV. pp. 45 and 71), do
not become brown.

_Water._—The determination of water may be made by weighing out about 5
grms. of the butter in a platinum dish and placing it in a hot-air oven
at a temperature of 100°-105° C., the drying being continued until the
weight is constant.

_Examination of the Fat._—A quantity of the butter fat is prepared by
heating about 50 grms. of the sample on the top of a water-bath until
it has completely melted, and the water and casein have separated to
the bottom, when the clear fat is decanted off and filtered through a
dry, warm filter paper. The filtered fat should be clear and bright,
and is then ready for examination.

Many of the general methods already described for the examination of
oils and fats are applicable, and furnish useful information as to the
purity of butter. Such, for example, are the specific gravity, the
saponification value, the refractive power, and Valenta’s acetic acid
test, the variations in which are discussed on p. 102.

_Refractive Power._—The instrument most usually employed is the Zeiss
butyro-refractometer, which consists of an Abbé double prism, which
opens for the reception of a few drops of the melted and, preferably,
filtered fat. A telescope is attached for reading the refraction on an
arbitrary scale graduated from 5°-105°. The prism should be maintained
at 40° C. while the observation is being made. At this temperature the
reading for pure butter is usually about 35°-38°. If the temperature is
above 40° subtract 0·55° for each degree above, and if below 40° C. add
0·55° for each degree below.

_Valenta’s Acetic Acid Test._—Reference has already been made to the
value of this in the examination of butter fat (p. 48). The mixture of
2·75 grms. butter fat and 3 c.c. glacial acetic acid is warmed to 40°
C., when, if the butter fat is pure, the mixture should become clear.
If this is the case, the liquid is now allowed to slowly cool down with
constant stirring with a thermometer until it just becomes turbid,
which should take place at about 30°-40° C.

With the exception of the determination of the refractive power these
methods of examination have now very largely given place to processes
based on the presence of volatile fatty acids in butter, and on their
differentiation from the volatile fatty acids found in cocoanut oil
(see pp. 50 _et seq._).

[Illustration: FIG. 1.]

The modification of the Reichert process suggested by Wollny was, in
its essential details, that adopted for the determination of butter in
margarine by a Committee of the Society of Public Analysts appointed
in 1900 to confer with the Principal of the Government Laboratory. The
details of this process, which was formerly, until the large increase
in adulteration of butter with cocoanut oil, or margarine containing
cocoanut oil, the chief method for the examination of butter, are as
follows (_Analyst_, 1900, 311):—

Five grms. of the melted and filtered fat are weighed into a 300 c.c.
flask, of the form and size shown in the figure, and 2 c.c. of a
solution prepared by dissolving 98 per cent. sodium hydroxide in an
equal weight of water, taking care to prevent absorption of atmospheric
carbon dioxide, and 10 c.c. alcohol (92 per cent.) are added. The
mixture is heated under a reflux condenser connected with the flask
by a T-piece for fifteen minutes in a bath containing boiling water.
The alcohol is distilled off by heating the flask on the water-bath
for about thirty minutes, or until the soap is dry. One hundred c.c.
of hot water, which has been kept boiling for at least ten minutes,
are added, and the flask heated until the soap is dissolved. Forty
c.c. of N/1 sulphuric acid, and three or four fragments of pumice or
broken pipe-stem, are added, and the flask is at once connected with
a condenser by means of a glass tube 7 mm. wide and 15 cm. from the
top of the cork to the bend. At a distance of 5 cm. above the cork
is a bulb 5 cm. in diameter. The flask is supported on a circular
piece of asbestos 12 cm. in diameter, having a hole in the centre 5
cm. in diameter, and is first heated by a very small flame to melt
the insoluble fatty acids, though the heat must not be sufficient to
cause the liquid to boil. The heat is increased, and, when fusion is
complete, 110 c.c. of the liquid are distilled off into a graduated
flask, the distillation lasting about thirty minutes (twenty-eight
to thirty-two minutes). The distillate is shaken, 110 c.c. filtered,
transferred to a beaker, 0·5 c.c. of an alcoholic phenol-phthalein
solution (1 per cent.) added, and the filtrate titrated with N/10
sodium hydroxide or barium hydroxide until pink. A blank experiment is
carried out in precisely the same way, using the same reagents, and
omitting the fat, and the amount of N/10 alkali required to neutralise
this distillate should not exceed 0·3 c.c. The difference between
the volumes of alkali required with the butter fat and in the blank
determination, multiplied by 1·1, gives the Reichert-Meissl-Wollny
value.

The improvements in the methods of refining cocoanut oil during recent
years have led to the addition of considerable quantities of cocoanut
oil to edible fats, and thus has somewhat reduced the value of this
process for distinguishing pure from adulterated butter, owing to
the fact already mentioned, that cocoanut oil contains a distinct
quantity of volatile fatty acids. A very large number of methods have
been proposed for detecting cocoanut oil in butter, and such terms
as “silver value,” “caprylic acid value,” “oxygen equivalent,” have
appeared in the literature of the subject.

Probably the most valuable of all these tests is one devised by
Polenské (_Zeit. Untersuch. Nahr. Genussm._, 1904, vii. 273-280), which
is based upon the determination of the volatile insoluble fatty acids
that distil over in the Reichert-Wollny process. This method, which is
known as the Reichert-Wollny-Polenské process, is now very generally
employed for the analysis of butter, but to obtain concordant results
it must be carried out strictly under the specified conditions and in
an apparatus of the form and dimensions shown in the figure (Fig. 2).
The details of the process are as follows:—

Five grms. of the clear butter fat are weighed out into a 300 c.c.
flask, and saponified as described on p. 111, with 20 grms. glycerin
and 2 c.c. of a 50 per cent. aqueous solution of sodium hydroxide, the
heating being effected with a Bunsen burner. When saponification is
complete and the mixture perfectly clear, it is allowed to cool down
below 100° C., and the soap dissolved in 90 c.c. of water. To this
solution, which should be clear and almost colourless, are now added 50
c.c. of dilute sulphuric acid containing 2·5 per cent. sulphuric acid
and some fragments of pumice, and the flask attached to the condenser.
The distillation is now proceeded with as usual, the heat being so
regulated that 100 c.c. of distillate passes over in nineteen to twenty
minutes, and the temperature of the condensing water is between 18°
and 20° C. As soon as 110 c.c. of distillate have been collected the
receiver is changed, and a 25 c.c. cylinder put in its place. The
receiver is now transferred (care being taken to mix its contents as
little as possible) to a water-bath at a temperature of 10° C., where
it is kept for ten minutes, the surface of the water being just above
the 110 c.c. mark. The insoluble fatty acids rise into the neck of the
flask, and, in the case of butter, are in the form of solid, opaque
granules, and with pure cocoanut oil in the form of clear, oily drops.
The latter are also obtained in the case of mixtures containing more
than 10 per cent. of cocoanut oil. The liquid is mixed and filtered,
the Reichert-Wollny value being determined on the filtrate by titration
with N/10 alkali.

The condenser, cylinder, and receiver are now washed with 18 c.c. of
water, the washings being passed through the filter paper, and the
insoluble fatty acids remaining on the filter dissolved in alcohol.
The solution obtained is titrated with N/10 barium hydroxide solution,
using phenol-phthalein as indicator, the number of c.c. required being
termed the “new butter value” of the fat.

This value was stated by Polenské to range, for pure butters having
Reichert-Meissl values of 23·3-30·1, from 1·5-3·0, and for cocoanut
oils having Reichert-Meissl values of 0·8-7·7, from 16·8-17·8.
Mixtures with Reichert-Meissl values between 23 and 27 gave “new
butter values” of from 1·6-1·9, a rise of 1·0 in the Reichert-Meissl
figure corresponding with an increase of 0·1 in the “new butter
value,” and each per cent. of cocoanut oil increasing the new butter
value by 0·1 above that given by a genuine butter possessing the same
Reichert-Meissl value. By this method it is possible to detect the
presence in butter of 10 per cent. and upwards of cocoanut oil.

A process similar in principle, but differing in method has been
proposed by Muentz and Coudon (_Ann. d. l’Inst. Agron._, 1904, iii.,
Part I.; _Analyst_, 1905, 155). In this, 10 grms. of the fat, melted
and weighed at 60° C., are placed in a cylindrical vessel, and
saponified by first stirring for ten minutes with 5 c.c. of potassium
hydroxide solution, containing 120 grms. potassium hydroxide in 100
c.c., and then heating to 70°-80° for twenty minutes. The saponified
fat is washed into a distilling flask with 200 c.c. of water, gently
warmed until solution is complete, and the fatty acids liberated by
adding 30 c.c. of phosphoric acid (sp. gr. 1·15), any carbon dioxide
being removed by connecting the vessel with a pump for ten minutes.

[Illustration: FIG. 3.]

The volatile fatty acids are then distilled off in the apparatus shown
in Fig. 3, and to obtain comparative results, strict adherence to the
form and dimensions given must be made. Two hundred c.c. are distilled
over, the heat being regulated so that this takes about one and a half
hours, and the distillate is allowed to stand until the following day,
when it is filtered through a wet paper, the flask washed with 5 c.c.
of water, which is also passed through the paper, and the soluble fatty
acids titrated with standardised lime-water, with phenol-phthalein as
indicator.

The filter is now washed with four successive quantities of 5 c.c. of
alcohol, poured on drop by drop, and the washings collected in the
receiver originally used. The condenser is next rinsed, first with 20
c.c. of alcohol, which should fill the tube when closed at its lower
end, and a second time with 5 c.c. of alcohol, these washings being
added to the remainder, and the whole titrated with the standard
lime-water.

The results of both titrations are expressed as butyric acid, and the
ratio

insoluble acids
———————————————— × 100
soluble acids

for pure butter should lie between 10 and 15, whilst for cocoanut oil
it is 250-280. For butter containing 10 per cent. of cocoanut oil the
figure is 19·8, and 15 per cent. cocoanut oil 24·1, for 20 per cent.
cocoanut oil 27, and for 50 per cent. cocoanut oil 73·1. It is claimed
that by this process the presence in butter of as little as 5 per cent.
of cocoanut oil can be detected with certainty.

Two methods have been proposed, based on the precipitation of insoluble
silver caprylate: (1) by Kirschner (_Zeit. Untersuch. Nahr. Genussm._,
1905, ix. 65-70), and (2) by Wijsman and Reijst (_Zeit. Untersuch.
Nahr. Genussm._, 1906, xi. 267-271).

In the former process, 5 grms. of the fat are treated by the
before-mentioned Reichert-Meissl-Wollny process so far as neutralising
100 c.c. of the filtered distillate with N/10 barium hydroxide
solution. Half a grm. of silver sulphate is then added to the neutral
solution, which is frequently shaken for one hour, and filtered, and
100 c.c. of the filtrate are transferred to a distilling flask. To
this liquid are now added 35 c.c. of dilute sulphuric acid (2½ per
cent.) and a few fragments of pumice, and the whole distilled until
110 c.c. of distillate have been obtained. This is filtered, and 100
c.c. titrated with N/10 barium hydrate solution, the number of c.c.
required; calculated back to the 5 grms., giving what is termed the
“second titration value.”

According to Kirschner, the percentage of butter fat in a mixture of
butter and cocoanut oil may be calculated from the formula:—Percentage
of butter fat = 4·319 S - 0·456 R - 2·15, where S = the second
titration value, and R = the Reichert-Meissl figure. A similar formula
is given for the percentage of cocoanut oil, which = 7·42 R - 8·116 S
- 3·57. Wijsman and Reijst’s method, or the “_silver value_ method,”
is performed by treating with silver nitrate (1) the Reichert-Wollny
distillate; and (2) 250 c.c. filtered from 300 c.c. of distillate
obtained from a further 5 grms. of fat, this being saponified, treated
with acid, and 100 c.c. distilled off in the usual way, after which
100 c.c. more water are added from a tap funnel, and another 100 c.c.
distillate collected, this being once more repeated.

In both cases the filtered solutions are neutralised with N/10 alkali,
and 40 c.c. of N/10 silver nitrate solution added, the precipitated
silver salt collected on a filter and washed until about 200 to 300
c.c. of filtrate have been collected, after which 50 c.c. of N/10
sodium chloride solution is added and the excess of chloride titrated
back with N/10 silver nitrate solution, potassium chromate being used
as indicator.

Eleven-tenths of the number of c.c. required in the first case, and
six-fifths of that used in the second, give what are termed the first
and second “silver values.”

In the case of pure butter all the caprylic acid should distil over in
the first 110 c.c. so that the “second silver value” should not exceed
the first, but with cocoanut oil the distillation of caprylic acid
continues with the second and third 100 c.c. of distillate, so that the
second silver value is greater than the first. The process has been
adversely criticised by Jean (_Ann. de Chim. Anal._, 1906, ii. 121-124).

A useful qualitative test for the detection of even small quantities
of cocoanut oil in butter is that due to Hinks (_Analyst_, 1907, 160).
In this, 5 c.c. of the melted and filtered fat are dissolved in 10
c.c. of ether, and cooled to 0° C. for thirty minutes. The solidified
glycerides are then rapidly filtered off, the filtrate evaporated, and
the residue redissolved in 3 to 4 times its volume of boiling 96 to 97
per cent. alcohol. This is allowed to cool to the ordinary temperature,
and then placed in a water-bath at 5° C., at which temperature it is
kept for fifteen minutes. The alcoholic layer is filtered off into
a tube cooled to 0° C., and the flocculent precipitate, which soon
separates, is examined microscopically with a magnification of 250-300.
Butter treated in this manner deposits round, granular masses, whereas
cocoanut oil gives fine needle-shaped crystals. As little as 5 per
cent. cocoanut oil may be detected by this process.

Ross (_Analyst_, 1908, 457) has attempted to make this process
quantitative by determining the refraction of the residues obtained,
but without success.

Palm oil in butter may be detected by the Liebermann-Storch reaction
for rosin. Ten c.c. of the filtered fat are dissolved in 10 c.c. of
acetic anhydride, and 1 drop of sulphuric acid (sp. gr. 1·53) added.
The mixture is shaken, and, on standing, a blue liquid, having a
greenish tint, separates, if palm oil is present.

=Soluble and Insoluble Fatty Acids—the Hehner value.=—A weighed
quantity of about 5 grms. of the filtered butter fat is introduced
into a strong 6 oz. bottle, and 50 c.c. of approximately N/2 alcoholic
potassium hydroxide solution added, another 50 c.c. being also
placed in an empty flask. The bottle is fitted with an india-rubber
stopper, which is secured by wire, and is placed in a water-bath, being
occasionally removed, and well agitated without bringing the liquid in
contact with the stopper. After about thirty minutes, saponification
is complete (this being shown by the contents of the bottle being
free from oily globules), and the bottle is withdrawn and allowed to
cool. The stopper is then removed, and the contents of the bottle
transferred, by rinsing with boiling water, into a 10 oz. flask, which
is placed, together with the flask containing only alcoholic potassium
hydroxide solution, on a steam-bath.

As soon as all the alcohol has evaporated the contents of each flask
are neutralised with N/2 hydrochloric acid, an excess of about 1
c.c. of acid being added, and a note made of the quantity used. The
flask containing the butter fat is nearly filled with boiling water,
and placed on the water-bath, a cork with a long upright tube being
inserted. When the fatty acids have melted to a clear liquid on the
surface of the water, the flask is removed and its contents allowed to
become perfectly cold, when the fatty acids should solidify. By gently
tapping the sides of the flask this cake is detached, and the liquid is
poured through a filter into a large flask. This liquid should have a
distinct odour of butyric acid, especially on warming.

The flask containing the insoluble fatty acids is again filled with
boiling water, the cork and reflux tube inserted, and the liquid
gently heated to the boiling-point, after which the flask is removed
and thoroughly shaken until the melted fatty acids are emulsified with
the water. The fatty acids are now allowed to separate again on the
surface, solidified by cooling, detached by gently tapping, and the
liquid filtered off as before. The process is repeated three times, or
until the washings collected separately do not require more than 0·2
c.c. of N/10 sodium hydroxide solution for neutralisation.

The mixed washings are next diluted to one litre or other convenient
volume, and an aliquot part titrated with N/10 sodium hydroxide
solution, the number of c.c. required being calculated upon the whole
liquid. This amount of alkali is that required to neutralise the excess
of acid added after saponification, together with the soluble fatty
acids, and the former may be known by titrating the excess in the blank
experiment, so that the difference between these two titrations gives
the alkali absorbed by the volatile fatty acids. These are usually
expressed as butyric acid, C₃H₇COOH, the percentage of which may be
found by multiplying the number of c.c. of alkali solution required to
neutralise the soluble fatty acids by 0·0088 and by 100, and dividing
by the weight of fat taken.

_The Insoluble Fatty Acids_ are determined by allowing the flask
containing the solid cake to drain as completely as possible, melting
the fatty acids, and pouring them on to the wet filter through which
the solution of soluble fatty acids was passed. They are then washed
on the filter with boiling water, and the funnel filter transferred to
a small beaker and placed in the water-bath until all the fatty acids
have filtered through. Flask, funnel, and filter paper are well washed
with ether, the washings added to the filtered fatty acids, and the
ether evaporated. The fatty acids are then dried in the oven at 100° C.
until constant in weight, and from the weight obtained the percentage
of insoluble fatty acids is calculated on the weight of butter fat
taken. This is known as the Hehner value.

Butter should contain at least 5 per cent. of soluble fatty acids
calculated as butyric acid, and the insoluble fatty acids should not
exceed 89½, rarely 88½ per cent.

The following table contains results obtained by Thorpe (_Journ. Chem.
Soc._, 1904, 254) on 357 samples of British butters:—

LEGEND:
(A) = Reichert-Meissl-Wollny Number.
(B) = Saponification Equivalent.
(C) = Refactometer Number at 45° C.
(D) = Soluble Acids per cent. on Fat.
(E) = Insoluble Acids per cent. on Fat.
(F) = Mean Molecular Weight of Insoluble Acids.
+----------+------+----------+-------+------+-----+------+-------+
| | | Specific | | | | | |
| Number | | Gravity | | | | | |
| of | (A) | at | (B) | (C) | (D) | (E) | (F) |
| Samples. | | 37·8° C. | | | | | |
+----------+------+----------+-------+------+-----+------+-------+
| 7 | 22·5 | 0·9101 | 255·4 | 42·0 | 4·3 | 90·1 | 266·9 |
| 17 | 23·5 | 0·9104 | 253·4 | 41·5 | 4·5 | 89·7 | 265·5 |
| 15 | 24·5 | 0·9108 | 251·3 | 41·5 | 4·7 | 89·4 | 265·0 |
| 27 | 25·5 | 0·9110 | 251·1 | 41·3 | 4·8 | 89·3 | 264·2 |
| 37 | 26·5 | 0·9113 | 248·9 | 41.0 | 4·9 | 88·9 | 261·9 |
| 51 | 27·5 | 0·9114 | 247·4 | 40·6 | 5·2 | 88·7 | 261·7 |
| 78 | 28·8 | 0·9118 | 245·7 | 40·1 | 5·4 | 88·4 | 260·9 |
| 56 | 29·5 | 0·9120 | 244·0 | 40·1 | 5·6 | 88·3 | 259·6 |
| 41 | 30·5 | 0·9123 | 242·4 | 39·9 | 5·8 | 87·9 | 260·1 |
| 18 | 31·3 | 0·9125 | 241·5 | 39·7 | 5·7 | 87·9 | 258·0 |
| 10 | 32·6 | 0·9130 | 241·2 | 39·4 | 6·0 | 87·7 | 257·8 |
| | | | | | | | |
| 357 | | | | | | | |
+----------+------+----------+-------+------+-----+------+-------+

=Casein (Curd).=—This may be estimated by transferring the dry butter
used in determining the water to a dry filter of known weight, washing
it thoroughly with ether or petroleum spirit until free from fat, and
weighing the filter after drying at 100° C. The residue includes casein
and salt, and the latter may be determined as described below, and
subtracted from the total residue.

The amount of casein does not usually exceed 1 to 2 per cent., but
cases are recorded when adulteration with casein has been practised,
and as much as 5 to 6 per cent. found.

=Salt.=—For most practical purposes, the ash remaining after burning
either the dried butter, or the residue insoluble in ether, may be
taken as salt (sodium chloride). If desired, the sodium chloride may be
estimated by extracting the butter with 10 to 20 c.c. of hot water in a
separating funnel, separating the aqueous layer, repeating this about
ten to fifteen times, and titrating the aqueous washings with standard
silver nitrate solution, using potassium chromate as indicator.

The proportion of salt may vary from 0·5 for a fresh butter up to 11
per cent. for a salt butter, but should not go beyond the latter limit
(see also p. 41).

=Colouring Matters.=—The natural colouring matter of butter, which
is termed “lactochrome,” is insoluble in alcohol or glacial acetic
acid, so that if on shaking the sample with either of these reagents
a coloured extract is obtained, artificial colouring matter has
undoubtedly been added.

Two general schemes have been devised for the detection of artificial
colouring matters in butter or margarine: (1) devised by Leeds
(_Analyst_, 1887, 150), in which the fat and colouring matter are first
extracted with petroleum ether, and the colouring matter dissolved
out of the ethereal extract with N/10 potassium hydroxide, and
reprecipitated with dilute hydrochloric acid; and (2) that devised by
Cornelison (_Journ. Amer. Chem. Soc._, 1908, 1478), who extracts the
colouring matter directly by means of glacial acetic acid.

Leeds’ process is carried out by mixing 100 grms. of the sample with
300 c.c. light petroleum spirit (sp. gr. 0·638), separating the
ethereal layer by means of a separating funnel, and washing it with 100
c.c. of water in successive small quantities. The ethereal extract is
allowed to stand for fifteen to twenty hours surrounded by ice, and is
then decanted from any separated “stearin” and shaken with 50 c.c. of
N/10 potassium hydroxide solution. The alkaline extract is separated,
made faintly acid with dilute hydrochloric acid, and the precipitated
colouring matter filtered off, together with a trace of fatty acid,
which is always dissolved out by the alkali. The colouring matter may
then be identified by the tests given on the preceding page.

In Cornelison’s method 10 grms. of the melted fat are thoroughly shaken
with 10 to 20 grms. of glacial acetic acid, at about 35° C., the
mixture allowed to separate, and the acid liquid drawn off. The colour
of the latter is noted, and portions treated with various reagents to
identify the colouring matter. The table on p. 125 gives the results
obtained with the colouring matters mentioned, incorporated with pure
butter in the proportion of 1 part in 100,000.

PRESERVATIVES (see p. 46).

The amount of boron compound may be readily estimated by Richmond and
Harrison’s modification of Thomson’s process. Twenty-five grms. of
the sample are weighed into a 100 c.c. stoppered cylinder, and, after
determination of the moisture present, sufficient water is added to
bring the total volume of water up to such a quantity that 1 c.c.
corresponds to 1 grm. of butter. From 10 to 15 c.c. of chloroform are
now introduced, and the contents of the flask heated, shaken, and
allowed to separate. An aliquot portion of the aqueous liquid is then
removed by means of a pipette, evaporated to dryness, ignited, and the
residue extracted with hot water. The extract is made neutral to methyl
orange, boiled to expel carbon dioxide, half its volume of neutral
glycerin added, and the mixture titrated with N/10 sodium hydroxide
solution until pink to phenol-phthalein. Each c.c. of N/10 sodium
hydroxide solution is equivalent to 0·0062 grms. of boric acid.

Another method, devised by Richmond and Harrison (_Analyst_, 1902,
181), is to weigh out 25 grms. of the sample in a beaker, add 25
c.c. of a solution containing 6 grms. of milk sugar and 4 c.c. of
N/1 sulphuric acid, in 100 c.c. of water. The beaker is placed in a
water-oven until the fat has just melted, and the contents are then
stirred well, allowed to separate, and 20 c.c. of the aqueous liquor
withdrawn. A few drops of phenol-phthalein are then added, and the
liquid heated to the boiling-point, and titrated with N/2 sodium
hydroxide solution until faintly pink, after which 12 c.c. of glycerin
are added, and more N/2 sodium hydroxide solution run in until a faint
pink colour is again obtained. The amount of alkali required in the
second titration, less the alkali required to neutralise 12 c.c. of
the glycerin, multiplied by 0·0368, gives the amount of boric acid in
20 c.c. of the aqueous extract, and the percentage may be calculated
by multiplying by (100 + percentage of water in the butter), and
dividing by 20. In an average butter the number of c.c. of N/2 sodium
hydroxide solution used, multiplied by 0·2, approximates closely to the
percentage of boric acid.

The best method of testing for benzoic acid, salicylic acid, fluorides,
and [Greek: b]-naphthol is to extract the melted butter with a dilute
solution of sodium bicarbonate, and to examine this extract for the
various preservatives.

Thus, in testing for benzoic and salicylic acids, the alkaline extract
is exactly neutralised with dilute hydrochloric acid, and a solution of
ferric chloride added. If benzoic acid or a benzoate has been added,
a buff-coloured precipitate will be immediately thrown down, and if
salicylic acid has been employed, an intense violet coloration will be
produced.

Numerous methods have been suggested for detecting even very minute
admixtures of benzoic acid or benzoates, among which may be mentioned
those of Halphen (_Journ. Pharm. Chim._, 1908, 201) and Robin (_Ann. de
Chim. Anal. Appl._, 1908, 431).

Halphen’s test depends on the conversion of the benzoic acid into
ammonium diamido-benzoate, which, in alkaline solution, has a brown-red
colour. A quantity of the butter is melted with sufficient lime-water
to render the aqueous liquor which separates distinctly alkaline. After
cooling, the latter is separated, acidified with phosphoric acid, and
extracted with ether. The ether is allowed to evaporate spontaneously,
and the residue dried at the ordinary temperature, after which it
is gently heated with 2 c.c. of concentrated sulphuric acid until
completely dissolved. An addition of 0·2 c.c. of fuming nitric acid is
now made, and the solution transferred to a dry test tube and heated
carefully over a small flame until sulphuric acid fumes appear. After
cooling, the mixture is diluted with 5 or 6 c.c. of water, which causes
nitrous fumes to be evolved. When again cold, a saturated solution of
sodium sulphite is added drop by drop until all yellow vapours have
disappeared. Ammonia is then allowed to flow over the surface of the
solution, and if benzoic acid is present, an orange-red coloration is
produced, the intensity of which is proportional to the quantity of
benzoic acid. In case no coloration is produced, the absence of benzoic
acid may be confirmed by adding a drop of ammonium sulphide to the
ammoniacal solution, when, if benzoic acid is present, a red coloration
develops at the point of contact of the two liquids.

By Robin’s process it is claimed that as little as 12 parts per 100,000
of sodium benzoate may be detected with certainty. The test is carried
out by shaking 25 grms. of the melted butter with a solution of 0·4 to
0·5 grm. of sodium bicarbonate in 50 c.c. of water, and 15 c.c. of 95
per cent. alcohol, and allowing the mixture to stand for ten minutes,
after which the alcoholic layer is drawn off, acidified with 7 or 8
drops of hydrochloric acid, and heated to the boiling-point. It is then
shaken with a little talc, and filtered, the cold filtrate extracted
in a separating funnel with 40 c.c. of ether, and the ethereal extract
washed once with a mixture of 20 c.c. of water, 5 c.c. of 95 per cent.
alcohol, and 0·2 to 0·3 grm. of sodium bicarbonate. The alkaline
alcoholic extract is evaporated on the water-bath, and the residue
carefully warmed with a mixture of 5 c.c. of concentrated sulphuric
acid and 10 drops of fuming nitric acid, until white fumes appear,
after which the liquid is poured into 50 c.c. of water containing
a small piece of turmeric paper. A yellow coloration indicates the
presence of benzoic acid, which may be confirmed by adding ammonia
solution until alkaline, then a few drops of ammonium sulphide
solution, and shaking the vessel. In the presence of benzoic acid the
colour changes from yellow to reddish orange.

=Fluorides.=—The presence of these may be detected in the absence of
boric acid by evaporating a small quantity of the alkaline extract
to dryness in a platinum crucible, igniting the residue, moistening
it with a few drops of concentrated sulphuric acid, and covering the
mouth of the crucible with a piece of glass, coated with paraffin wax,
through which some marks have been scratched.

Fluorides may also be detected by applying the above process to the
aqueous liquor, which separates when a sample of the butter is melted.

If boric acid is present, the fluoride is liable to be lost by
volatilisation as boron fluoride. It is necessary, therefore, to
separate the borate as calcium borate, by rendering the liquid alkaline
with lime-water, evaporating it to dryness, and extracting the residue
with dilute acetic acid, which dissolves calcium borate. The insoluble
matter is then dried, and treated with concentrated sulphuric acid as
described above.

MARGARINE, VEGETABLE BUTTER, OR OTHER BUTTER SUBSTITUTES

The analysis of these is a matter requiring a considerable amount of
skill, and even when the analysis is made, very long experience is
necessary before a right interpretation can be put upon the chemical
and physical data obtained.

The only requirements for margarine under the Sale of Food and Drugs
Act, 1899, are that the sample shall not contain more than 16 per cent.
water or more than 10 per cent. of butter. The same restrictions as to
preservatives apply to this as to genuine butter.

The amount of water is readily determined by the method given under
“Butter” (p. 109). The method officially adopted by the Committee of
the Society of Public Analysts for the estimation of butter is the
Reichert-Meissl-Wollny process (p. 111), the maximum permissible limit
for the Reichert-Wollny value being 4, and a Reichert-Wollny value of
7·1 being regarded as indicative of the presence of 20 per cent. butter
fat.

In addition to the analysis of margarine to ensure compliance with
these standards, it is often desirable to endeavour to determine the
precise composition of a sample of artificial butter, such as the
relative proportions of animal and vegetable fats, and the particular
fats or oils of which they consist. It is here where only prolonged
experience can decide what tests to apply and determine the correct
interpretation to put upon the results obtained.

In an exhaustive analysis, the specific gravity, saponification value,
iodine value, titre, and Reichert-Wollny-Polenské figures should always
be determined, and such qualitative tests as Halphen’s for cotton-seed,
Baudouin’s for sesame, the arachidic acid test for arachis oil, and the
Liebermann-Storch test for palm oil applied.

The tests for colouring matters and preservatives are the same as for
natural butter.

LARD

In addition to the tests mentioned in Chapter V. pp. 60 _et seq._,
Halphen’s test for cotton-seed oil and Baudouin’s test for sesame oil
should be applied, and, if thought desirable, arachis oil may be tested
for by the arachidic acid method. The presence of as little as 2 to 3
per cent. cotton-seed oil may be detected by the phytosteryl acetate
test (see p. 101), and the addition of maize oil, which is sometimes
used for adulterating lard, will also be shown by the same method.

Preservatives may be detected, and, if present, estimated as described
under “Butter.”

CHEESE

The composition of cheese is so variable that it is to be regretted
there are no standards to which it should conform.

The proportion of fat may vary from 20 per cent. or less to 35 or 40
per cent., or, in a cream cheese, up to 75 per cent., while the water
may be anything between 20 and 40 per cent.

The analysis of cheese should include determinations of the proportions
of water, ash, fat, and nitrogen, and an examination of the fatty
matter.

_Water._—This may be determined by drying a weighed quantity of about 5
grms. of the sample, cut in thin slices, in the oven at 105° C., until
constant in weight.

_Ash._—The dried cheese, as obtained in the above determination, is
ignited at as low a temperature as possible, and the residue weighed
when the whole of the carbon has been burned away.

_Fat._—This may be determined approximately by grinding up 25 to 50
grms. of the dried cheese with ignited sand, and extracting the mixture
in a Soxhlet apparatus with ether or petroleum spirit, the extract
being collected in a weighed carbonic acid flask, from which the
solvent is afterwards distilled off, and the residue dried in the oven
at 105° C., and weighed.

A better method is that of Palmquist, which is a modification of the
Rose-Gottlieb process. In this, about 1 grm. of the cheese is weighed
into a Gottlieb tube, 10 c.c. of 2·5 per cent. ammonia solution added,
and the mixture warmed on the water-bath, and shaken until a milky
homogeneous solution is obtained. After cooling, 10 c.c. alcohol and 25
c.c. of ether are added, the tube being thoroughly shaken after each
addition. An addition of 25 c.c. of petroleum spirit is then made, and
the tube, after being again well shaken and inverted, is allowed to
stand for a few hours for its contents to separate, after which the
ethereal layer is siphoned into a weighed flask. A second extraction
of the mass remaining in the tube is then carried out in an exactly
similar manner, the ethereal extract being again siphoned into the
weighed flask, the solvent distilled off, and the residue dried in the
oven at 105° C., and weighed.

A larger quantity of the fat for its examination may be readily
prepared by cutting up a quantity of the cheese, wrapping it in a
piece of muslin, and suspending over a basin in an oven at 105° C. The
clear fat collected should then be examined, and its Reichert-Wollny
value, which should be similar to that of butter, determined. If the
Reichert-Meissl-Wollny figure is abnormal, the fat requires further
systematic examination by the processes mentioned under “Margarine” (p.
130), to detect foreign fats.

_Nitrogen._—This is estimated by heating 1 to 2 grms. of the cheese
with concentrated sulphuric acid and a globule of mercury, as in
the well-known Kjeldahl process. The proteins may be calculated by
multiplying the percentage of nitrogen by 6·3.

CHOCOLATE

No standards have yet been legally fixed in this country for any of
the various forms of chocolate, though such standards are in existence
on the Continent, and are urgently needed in view of the large amount
of adulteration practised in this industry. Not only is the natural
fat of the chocolate replaced by other fats, such as cocoanut oil, and
cocoanut stearin, or palm-nut stearin, and the chocolate adulterated
with excessive husk or starch, but products are sold as milk or cream
chocolate which have no right to such designations. Hence N. P. Booth
presented to the International Congress of Applied Chemistry, held in
London last year, the following proposed standards, which are not more
stringent than those adopted by some Continental countries and by some
of the Colonies:—

1. _Unsweetened Chocolate_ must be prepared exclusively from roasted,
shelled, finely ground cocoa-beans, with or without the addition of a
small quantity of flavouring matter. It should contain not less than 45
per cent. of cacao butter.

2. _Sweetened Chocolate._—A preparation consisting exclusively of
the products of roasted, shelled, finely ground cocoa-beans, and not
more than 65 per cent. of sugar, with or without a small quantity of
harmless flavouring matter.

3. _Granulated or Ground Chocolate for Drinking Purposes._—The same
definition as for sweetened chocolate should apply here, except that
the proportion of sugar may be raised to not more than 75 per cent.

4. _Chocolate-covered Goods._—Various forms of confectionery covered
with chocolate, the composition of the latter agreeing with the
definition of a sweetened chocolate.

5. _Milk Chocolate._—A preparation composed exclusively of roasted,
shelled cocoa-beans, sugar, and not less than 15 per cent. of the dry
solids of full-cream milk, with or without a small quantity of harmless
flavouring matter.

The analysis of chocolate should comprise determinations of the
moisture, ash, fat, fibre, total nitrogen, and sugar, and an
examination of the nature of the fatty matter and sugar.

In the case of milk chocolate or cream chocolate, the fatty matter
should contain both cacao butter and butter fat, and the sugar should
contain lactose.

The analysis is carried out as follows:—

_Water._—A weighed quantity of about 5 grms. is finely divided, and
dried in the oven at 105° C., until constant in weight.

_Ash._—The dried product obtained in the determination of the moisture
is cautiously burnt until all carbonaceous matter is volatilised. The
proportion of ash should not exceed 1 to 1·5 per cent., unless the
sample has been coloured with mineral colouring matter, such as ochre.

_Fat._—This may be estimated by extracting 5 grms. of the finely ground
sample in an extraction thimble with ether or light petroleum spirit,
by means of a Soxhlet apparatus. The extracting liquid is collected in
a small weighed flask, which, when extraction is complete, is detached
from the Soxhlet apparatus, the solvent distilled off, and the residual
fat weighed, after being dried in the oven at 105° C.

Kreutz (_Zeit. Untersuch. Nahr. Genussm._, 1908, 584-586) recommends
melting the sample with chloral alcoholate prior to extraction with
ether. From 2 to 3 grms. of the chocolate are placed in a small flask
with 3 to 4 grms. chloral alcoholate, and the mixture melted by heating
on a water-bath. The hot mass is well stirred with 10 to 15 c.c. of
ether, a further 35 c.c. of ether added, and, after thorough shaking,
the mixture is filtered through a dry filter. The filtrate is passed
through the filter again and again until perfectly bright, and the
residue on the filter washed with ether three times. The ether is
then distilled off, and any chloral alcoholate removed by heating the
residue to about 75° C., under reduced pressure. The residue obtained
is extracted with carbon tetrachloride and filtered to eliminate a
little theobromine and colouring matter, the filtrate evaporated in a
weighed flask, and the residue of fat dried in the oven at 105° C., and
weighed.

For the examination of the fat a larger quantity may be prepared by
simply shaking up about 15 to 20 grms. of the finely ground sample
in a stoppered bottle with three or four successive quantities of
petroleum spirit, allowing the mass to settle, pouring off the
solvent, and evaporating it. The residual fat should then be examined
for its refractive power, its Reichert-Meissl-Polenské values, its
saponification value, its iodine value, and its titre.

Genuine cacao butter gives a refractometer reading at 35° C. of about
49°, has a Reichert-Meissl value of 1 or rather less, a saponification
value of about 286-290, an iodine value of about 34, and a titre of
about 48° C. Cocoanut oil has a refractive power of only about 37°,
and is thus readily detected by this, as also by the much increased
saponification value and reduced iodine value, and the increased
Reichert-Meissl figure.

Cocoanut stearin also increases the saponification value, reduces the
iodine value, and raises the Reichert-Meissl figure. Palm-nut stearin
increases the saponification value, reduces the iodine number, and
slightly raises the Reichert-Meissl figure, its own Reichert-Meissl
value being about 2·2.

Of the other fats said to be used as substitutes for cacao butter, and
mentioned in Chapter VII.

_Dika, or Gaboon Fat_, raises the saponification value, lowers the
iodine value, but does not affect the Reichert-Meissl figure.

_Borneo Tallow, or Tankawang Fat_, has analytical values very similar
to those of cacao butter.

_Illipé Fat_ has a much higher iodine value (54-60). (See also p. 87.)

_Fibre._—This is best estimated by Allen’s method (_Commercial Organic
Analysis_, iii., Part II., p. 567), in which 2 grms. are freed from
fat, and boiled for thirty minutes under a reflux condenser with 200
c.c. of water and 2½ c.c. of sulphuric acid. The liquid is filtered
through linen, and the residue thoroughly washed with hot water and
boiled with 200 c.c. of 1¼ per cent. solution of sodium hydroxide. The
residue is filtered off, washed with hot water, alcohol, and ether,
and dried at 110° C., and weighed. It is then ignited, and the loss
regarded as crude fibre.

_Total Nitrogen._—This is estimated on about 2 grms. of chocolate by
the Kjeldahl method. In an ordinary chocolate it is normally about
1 per cent., and in a milk chocolate slightly higher. In a plain
chocolate the proportion of nitrogen, multiplied by 20, will give the
percentage of fat-free cocoa.

_Sugar._—This may be determined in plain chocolate by means of a
polarimeter, a 20 per cent. aqueous solution, which is clarified with
lead acetate in the ordinary way, being used. In the case of milk
chocolate the introduction of lactose complicates the determination
slightly, but estimation of the copper-reducing power enables the
lactose to be calculated, and an allowance made for its effect on the
optical rotation.

[Illustration: FIG. 2.]

CHAPTER IX

STATISTICS OF THE TRADE IN EDIBLE OILS

In basing any conclusions as to the consumption of edible oils upon the
figures published by the Customs authorities of different countries,
allowance must be made for the fact that in many cases (_e.g._ seed
oils) it is not possible to distinguish the quantities used for food
from those used for soap and lubricating purposes.

=United Kingdom Trade.=—The following figures are taken from the tables
published annually by the Board of Trade, and show the import of oils
during the ten years ending 1908:—

+-----------------+--------------+--------------+--------------+
| Oils. | 1899. | 1900. | 1901. |
+-----------------+--------------+--------------+--------------+
|Cocoanut, cwts. | 458,297 | 552,743 | 478,143 |
|Olive, tuns | 15,939 | 12,044 | 15,488 |
|Palm, cwts. | 945,472 | 938,350 | 1,212,111 |
|Seed oils, tuns | 46,416 | 41,131 | 48,842 |
+-----------------+--------------+--------------+--------------+
| Oils. | 1902. | 1903. |
+-----------------+--------------+--------------+
|Cocoanut, cwts. | 495,860 | 782,632 |
|Olive, tuns | 18,978 | 14,485 |
|Palm, cwts. | 1,446,298 | 1,234,004 |
|Seed oils, tuns | 35,454 | 36,011 |
+-----------------+--------------+--------------+

+-----------------+--------------+--------------+--------------+
| Oils. | 1904. | 1905. | 1906. |
+-----------------+--------------+--------------+--------------+
|Cocoanut, cwts. | 615,238 | 613,165 | 335,545 |
|Olive, tuns | 15,101 | 7,690[1] | 9,419[1] |
|Palm, cwts. | 1,309,176 | 1,144,368 | 1,223,787 |
|Seed oils, tuns | 10,553 | 3,309[1] | 1,786[1] |
+-----------------+--------------+--------------+--------------+
| Oils. | 1907. | 1908. |
+-----------------+--------------+--------------+
|Cocoanut, cwts. | 335,781 | 555,335 |
|Olive, tuns | 7,391[1] | 6,330[1] |
|Palm, cwts. | 1,508,023 | 1,317,995 |
|Seed oils, tuns | 1,111[1] | 2,203[1] |
+-----------------+--------------+--------------+

[Footnote 1: Not including refined oil.]

The amounts of the chief edible oils and their value imported into
this country during the three years ending 1909 were as follows:—

_Imports_

+------------------------+-----------+-----------+-------------+
| Oil. | 1907. | 1908. | 1909. |
+------------------------+-----------+-----------+-------------+
| _Crude_— | | | |
|Cocoanut, cwts. | 357,815 | 555,335 | 502,408 |
|Olive, tuns | 7,391 | 6,330 | 4,788 |
|Palm, cwts. | 1,508,023 | 1,317,995 | 1,762,641 |
| | | | |
| _Refined_— | | | |
|Cocoanut, cwts. | 118,903 | 203,077 | 177,085 |
|Cotton-seed, tuns | 14,226 | 15,251 | 17,560 |
|Olive, tuns | 4,937 | 5,822 | 4,186 |
|Palm, cwts. | 18,656 | 35,838 | 58,645 |
+------------------------+-----------+-----------+-------------+
|Butter, cwts. | 4,210,156 | 4,210,821 | 4,062,833 |
|Margarine, cwts. | 885,068 | 813,447 | 868,292 |
+------------------------+-----------+------------+------------+
|Lard from U.S.A., cwts. | 1,903,961 | 1,924,881 | 1,703,578 |
|Lard from other | | | |
| countries, cwts. | 61,170 | 62,610 | 56,707 |
+------------------------+-----------+------------+------------+
|Imitation lard, cwts. | 222,090 | 174,064 | 231,847 |
+------------------------+-----------+------------+------------+
| Oil. | 1907. | 1908. | 1909. |
+------------------------+-----------+------------+------------+
| _Crude_— | £ | £ | £ |
|Cocoanut, cwts. | 634,357 | 757,812 | 752,257 |
|Olive, tuns | 287,254 | 243,497 | 241,905 |
|Palm, cwts. | 1,896,133 | 1,559,266 | 2,195,620 |
| | | | |
| _Refined_— | | | |
|Cocoanut, cwts. | 223,522 | 323,334 | 315,690 |
|Cotton-seed, tuns | 365,512 | 401,506 | 482,139 |
|Olive, tuns | | | |
|Palm, cwts. | 251,634 | 293,308 | 276,743 |
+------------------------+-----------+------------+------------+
|Butter, cwts. |22,417,926 | 24,080,912 | 22,425,067 |
|Margarine, cwts. | 2,223,645 | 2,081,245 | 2,243,737 |
+------------------------+-----------+------------+------------+
|Lard from U.S.A., cwts. | | | |
|Lard from other | 4,491,539 | 4,407,410 | 4,857,199 |
| countries, cwts. | | | |
+------------------------+-----------+------------+------------+
|Imitation lard, cwts. | 408,192 | 306,700 | 438,909 |
+------------------------+-----------+------------+------------+

_Exports_

+---------------------+------+------+------+-------+-------+--------+
| Oil, etc. | 1907.| 1908.| 1909.| 1907. | 1908. | 1909. |
+---------------------+------+------+------+-------+-------+--------+
| _Crude_— | | | | £ | £ | £ |
|Cocoanut, cwts.|56,058|56,887|61,247| 95,074| 79,563| 89,327 |
|Olive, tuns | | 26| 70| | 1,341| 3,915 |
|Palm, cwts.| 4,946| 415| 1,787| 7,568| 543| 2,554 |
| _Refined_, | | | |846,037|705,020|822,923 |
|Butter, cwts.|12,305|10,045| 9,214| 68,591| 59,324| 54,825 |
|Lard, cwts.| 9,634| 8,118| 5,506| 26,340| 22,340| 18,722 |
|Imitation lard, cwts.| 568| 583| 792| 1,000| 1,008| 1,604 |
+---------------------+------+------+------+-------+-------+--------+

In the case of the crude oils mentioned in the above tables it is
probable that the bulk was used for technical purposes.

=Olive Oil.=—Large quantities of foreign olive oil are imported into
the French Riviera, the bulk coming from Italy and Tunis, and a small
proportion from Spain, Turkey, Algiers, and Greece.

According to statistics published by Slaus-Kantschlieder (_Chem. Rev.
Fett- u. Harz-Ind._, 1909, xvi. 223-231), the importations into Nice
amounted to 8,264,900 kilos in 1907, as compared with 11,917,200 kilos
in 1906.

The quantities of olive oil exported from Nice to various countries
during the two years were as follows:—

+----------------+---------+---------+
| Exported to— | 1906. | 1907. |
+----------------+---------+---------+
| | Kilos. | Kilos. |
|Austria-Hungary | 351,000 | 370,000 |
|Germany | 748,000 | 749,000 |
|Russia | 436,000 | 624,000 |
|England | 234,000 | 206,000 |
|Switzerland | 313,000 | 289,000 |
|Roumania | 70,000 | 123,000 |
|Servia | 14,000 | 21,000 |
|Bulgaria | 4,600 | 5,200 |
+----------------+---------+---------+

=Italian Trade in Olive Oil.=—The Italian Customs authorities give
the following details of the exports of refined and other grades of
olive oil during the three years ending 1907, the quantities being in
quintals (1 quintal = 220·46 lb.):—

_Refined Olive Oil_

+----------------+------------+------------+----------+
| Exported to— | 1907. | 1906. | 1905. |
+----------------+------------+------------+----------+
| | Quintals. | Quintals. | Quintals.|
|United States | 29,188 | 71,400 | 38,687 |
|Austria-Hungary | 28,998 | 22,203 | 7,752 |
|Germany | 15,690 | 11,132 | 5,490 |
|Great Britain | 5,861 | 9,432 | 4,102 |
|Holland | 12,648 | 73,519 | 8,403 |
|Switzerland | 7,626 | 11,294 | 6,936 |
|Egypt | 15,353 | 19,285 | 4,867 |
|Other countries | 8,536 | 8,894 | 4,900 |
+----------------+------------+------------+----------+
| Totals | 123,900 | 227,159 | 81,137 |
+----------------+------------+------------+----------+
| Total values | $1,471,122 | $2,051,652 | $945,600 |
+----------------+------------+------------+----------+

_Other Grades of Olive Oil_

+---------------------+-------------+-------------+------------+
| Exported to— | 1907. | 1906. | 1905. |
+---------------------+-------------+-------------+------------+
| | Quintals. | Quintals. | Quintals. |
|Austria-Hungary | 19,013 | 25,834 | 18,293 |
|France | 60,766 | 116,312 | 43,191 |
|Germany | 17,793 | 21,222 | 11,058 |
|Great Britain | 25,000 | 29,739 | 22,184 |
|Russia | 26,677 | 22,854 | 29,765 |
|Switzerland | 7,124 | 8,819 | 5,668 |
|Egypt | 2,636 | 5,810 | 1,956 |
|United States | 82,198 | 95,258 | 52,577 |
|Brazil | 14,495 | 12,320 | 8,820 |
|Argentina | 90,347 | 109,194 | 58,256 |
|Uruguay | 9,402 | 8,190 | 3,893 |
|Other countries | 32,976 | 33,032 | 17,440 |
+---------------------+-------------+-------------+------------+
| Totals | 388,427 | 488,584 | 273,101 |
+---------------------+-------------+-------------+------------+
| Total Values | $9,370,801 | $11,787,041 | $6,852,104 |
+---------------------+-------------+-------------+------------+
| Grand Totals | 512,327 | 715,743 | 354,238 |
+---------------------+-------------+-------------+------------+
| Grand Total Values | $10,861,923 | $13,838,693 | $7,797,704 |
+---------------------+-------------+-------------+------------+

=Spanish Oil Trade.=—Some interesting details of the production of
olive oil in Spain were given in the _Board of Trade Journal_ for
September 1907. The average output of the oil was estimated at 200,000
metric tons. In 1906 it amounted to 133,665 tons (metric), as against
149,249 tons in 1905. The deficiency in the crop of 1906 accounted for
the falling off of the exports of oil in that year, though owing to the
official pecuniary encouragement given to the manufacture of seed oils
in Spain, there was not a corresponding increase in the importations of
oils employed as substitutes for olive oil.

The imports of seed oils, cocoanut, and palm-nut oils and oil seeds
into Spain, and the exports of olive oil during the years 1905 and
1906, and the first six months of 1907, were as follows:—

_Spanish Oil Trade_

+-----------------------+--------------+--------------+------------+
| | | | First |
| | 1905. | 1906. | six months |
| | | | of 1907. |
+-----------------------+--------------+--------------+------------+
|_Imports_:— | Metric tons. | Metric tons. |Metric tons.|
| Seed oil | 684 | 895 | 330 |
| Cocoanut and palm-nut| 279 | 548 | 400 |
| oil | | | |
| Oil seeds | 39,526 | 45,233 | 32,917 |
|_Export_:— | | | |
| Olive oil | 34,228 | 18,911 | 6,150 |
+-----------------------+--------------+--------------+------------+

=Vegetable Oil Trade in France.=—The following details of the trade of
France in vegetable oils are given by the _Oil, Paint, and Drug Rep._,
April 4, 1910:—

During 1909, 141,080 metric tons of copra (cocoanut pulp) were imported
into France as against 169,357 tons in 1908, and 110,008 tons in 1907,
nearly the whole of the quantity going to Marseilles.

About 40 per cent. of the imports were from the Philippines, 29 per
cent. from the Dutch Indies, 9 per cent. from British India, 8 per
cent. from Mauritius, and the remainder from other countries.

The total values of oil products used in France in 1909 were officially
estimated at £2,044,500, including—Arachis nuts, £4,511,000; linseed,
£1,999,800; sesame seed, £892,000; mustard and Indian rape seed,
£864,000; poppy seed, £399,800; and cotton-seed (chiefly Egyptian),
£262,000.

The following figures show the imports of oil seeds into Marseilles
during the three years:—

+------------------------+---------+---------+---------+
| | 1907. | 1908. | 1909. |
+------------------------+---------+---------+---------+
| | Tons. | Tons. | Tons. |
|Sesame | 68,836 | 41,749 | 64,087 |
|Arachis nuts, shelled | 113,219 | 85,653 | 170,012 |
| ” ” unshelled | 123,304 | 102,188 | 155,056 |
|Linseed | 21,202 | 17,085 | 16,962 |
|Rape and ravison | 5,082 | 2,202 | 5,795 |
|Poppy seed | 4,106 | 2,334 | 2,356 |
|Castor seed | 16,370 | 18,111 | 11,553 |
|Pulghere | 520 | 709 | 1,818 |
|Cotton-seed | 15,884 | 14,497 | 14,249 |
|Niger and kapok | 6,351 | 3,701 | 5,118 |
|Copra | 109,744 | 163,999 | 136,655 |
|Palm kernels | 4,412 | 1,675 | 3,639 |
|Mowhrah, illipé, etc. | 12,781 | 11,146 | 8,856 |
+------------------------+---------+---------+---------+
| Totals | 501,811 | 465,049 | 596,156 |
+------------------------+---------+---------+---------+

The only oils imported in any quantities were cotton-seed, olive, and
palm oils, the average importations of which during the last five years
were:—

Tons.
Cotton-seed oil 24,000
Olive oil 22,000
Palm oil 16,000

The copra imported is chiefly used in the manufacture of soap, though
about a third is manufactured into edible cocoanut oil and vegetable
butters.

The cocoanut oil exported from Marseilles (chiefly to England, the
United States, Switzerland, and Austria) amounted to 23,840 tons in
1909, while 22,726 tons were sent from Marseilles to other parts of
France.

=Cotton-Seed Oil in the United States.=—The growth of the now gigantic
cotton-seed oil industry in the United States is illustrated by the
following figures given by the _Oil, Paint, and Drug Rep._, June 7,
1909, which show the production and exports of the seed and its product
since 1872:—

_Production of Cotton-Seed and Oil_

+------------+---------------------------+-------------+-----------+
| | Cotton-seed. | | Cake and |
|Year ending +-----------+---------------+ Oil | Meal |
| June 30. | Produced. | Manufactured. | Produced. | Produced.|
+------------+-----------+---------------+-------------+-----------+
| | Tons. | Tons. | Gallons. | Tons. |
| 1909 | 5,903,838 | 3,669,747 | 146,789,880 | 1,491,752 |
| 1908 | 4,952,402 | 2,564,873 | 103,049,820 | 1,043,080 |
| 1907 | 5,912,646 | 3,843,981 | 153,759,240 | 1,785,804 |
| 1906 | 5,060,205 | 3,131,175 | 125,700,928 | 1,271,740 |
| 1904 | 4,716,591 | 3,241,426 | 121,877,618 | 1,155,568 |
| 1902 | 4,630,311 | 3,154,417 | 118,606,079 | 1,124,550 |
| 1900 | 4,668,346 | 2,479,386 | 93,325,729 | 884,391 |
| 1890 | 3,494,811 | 873,702 | 34,948,000 | 305,800 |
| 1880 | 2,615,608 | 235,404 | 9,416,000 | 82,400 |
| 1875 | 1,686,516 | 84,325 | 3,373,000 | 29,500 |
| 1872 | 1,317,637 | 52,705 | 2,108,000 | 18,400 |
+------------+---------------------------+-------------+-----------+

_Exports_

+------------+------------------------+-------------------------+
| Year | Cotton-seed. | Oil. |
| ending +-----------+------------+------------+------------+
|June 30.[2] | Quantity. | Value. | Quantity. | Value. |
+------------+-----------+------------+------------+------------+
| | Tons. | $ | Gallons. | $ |
| 1909 | | | | |
| 1908 | 14,239 | 353,213 | 41,029,991 | 17,226,451 |
| 1907 | 8,814 | 209,493 | 41,880,304 | 17,074,403 |
| 1906 | 11,859 | 268,330 | 43,793,519 | 13,673,370 |
| 1904 | 6,430 | 141,174 | 29,013,743 | 10,717,280 |
| 1902 | 28,202 | 509,627 | 33,042,848 | 12,992,393 |
| 1900 | 24,928 | 346,230 | 46,902,390 | 14,127,538 |
| 1890 | 3,830 | 74,575 | 13,384,385 | 5,219,178 |
| 1880 | 6,071 | 134,116 | 6,997,796 | 3,225,414 |
| 1875 | 2,658 | 63,128 | 417,387 | 216,640 |
| 1872 | 3,180 | 72,212 | 547,165 | 293,546 |
+------------+-----------+------------+------------+------------+
| Year | Cake and Meal. |
| ending +-----------+------------+
| June 30. | Quantity. | Value. |
+------------+-----------+------------+
| | Tons. | $ |
| 1909 | | |
| 1908 | 464,644 | 11,889,415 |
| 1907 | 670,484 | 17,062,594 |
| 1906 | 555,417 | 13,073,100 |
| 1904 | 410,175 | 9,134,088 |
| 1902 | 525,233 | 12,271,009 |
| 1900 | 571,852 | 11,229,188 |
| 1890 | [3] | |
| 1880 | | |
| 1875 | | |
| 1872 | | |
+------------+-----------+------------+

[Footnote 2: The figures in this table relate to the seed crop of the
previous year.]

[Footnote 3: Not separately shown.]

INDEX

Acetic acid, 9.

=Acid=—
Acetic, 9.
Arachidic, 9.
Behenic, 9.
Butyric, 9.
Capric, 9.
Caproic, 9.
Caprylic, 9.
Carnaubic, 9.
Cerotic, 10.
Daturic, 9.
Doeglic, 10.
Eleomargaric, 12.
Eleostearic, 12.
Erucic, 10.
Ficocerylic, 9.
Hyænic, 10.
Hypogæic, 10.
Isolinolenic, 12.
Isovaleric, 9.
Jecoric, 12.
Lauric, 9.
Lignoceric, 9.
Linolenic, 12.
Linolic, 12.
Margaric, 67.
Melissic, 10.
Moringic, 10.
Myristic, 9.
Oleic, 10.
Palmitic, 9.
Physetoleic, 10.
Pisangcerylic, 10.
Psyllostearylic, 10.
Rapic, 10.
Ricinolenic, 12.
Stearic, 9.
Tariric, 12.
Telfairic, 12.
Theobromic, 10.
Tiglic, 10.
Acidity of lard, 61-62.
Acids, volatile fatty, 10.
Alkaline earths, refining with, 28.
Analysis of oil, 89.
Arachidic acid, 9.
Arachis oil, 18, 77, 78.
adulteration of, 78.
analysis of, 78.
constituents of, 78.
Artificial colouring matter in butter, 55, 122.
Artificial flavouring in margarine, 71, 72.
Azo dyes, 71.

Barium values, 55.
Bechi’s test, 107.
Behenic acid, 9.
Bleaching of oils, 29.
with charcoal, 29.
fuller’s earth, 30.
hydrosulphites, 33.
hyposulphites, 33.
organic peroxides, 33.
ozone, 32.
sodium bisulphite, 33.
Borax in butter, 46.
Boric acid in butter, 46.
Borneo tallow, 87.
Boron compounds, 124.
Bromine absorption, 96.
thermal value, 105.
Brown grease, 58.
=Butter=, 3, 39, 40.
abnormal, 49.
analysis of, 109.
artificial colouring matters in, 55, 122.
borax in, 46.
boric acid in, 46.
cacao, 19, 84, 85.
casein in, 121.
chemical characteristics of, 48-52.
cocoanut oil in, 53, 54, 112.
commercial, 40.
composition of, 40.
curd in, 41.
Dutch, 67.
fat, 39, 40.
composition of, 40.
Illipé, 87.
influence of food of cows on, 52.
Irish, 52.
keeping properties of, 42-44.
Mahua, 87.
milk-blended, 41.
nut, 72.
oil, 16, 45.
physical characteristics of, 47.
preservatives in, 46-47, 124.
“process,” 44-46.
rancidity of, 44.
refractometric examination of, 48.
renovated, 44-46.
salt in, 41.
shea, 21, 87.
solubility of, 47.
vegetable, 16, 72.
water in, 41.
Butterine, 67.
Butyric acid, 9.
Butyrin, 6, 7.
Butyro-refractometer, 48.

Cacao butter, 19, 84-85.
Cadmium values, 55.
Capric acid, 9.
Caprin, 6.
Caproic acid, 9.
Caproin, 6.
Caprylic acid, 9.
Caprylin, 6.
Carnaubic acid, 9.
Casein in butter, 121.
Caustic soda, refining with, 26.
Cerotic acid, 10.
Ceylon oil, 16.
Charcoal, bleaching with, 29.
Cheese, 130.
Chemical methods of refining, 132.
Chocolate, 84, 132.
Chocolate cream, 85.
Chocolate fats, 84-88, 133.
Choice lard, 58.
Choice steam lard, 58.
Cochin oil, 16.
Cocoa, 84.
Cocoanut oil, 15.
analyses of, 86.
deodorisation of, 34.
in butter, 53, 54, 112.
stearins, 85, 86.
Colouring matter for margarine, 71.
matters, artificial, in butter, 55.
Combustion of fats, 2.
Commercial butter, 40.
grades of lard, 58-59.
Constitution of fats, 1, 3.
oils, 1, 3.
Corn oil, 83, 84.
Cotton-seed oil, 16, 80, 107.
winter, 81.
stearin, 17, 81.
Coumarine, 72.
Crystals of lard, 59, 60.
Culinary oils, 74.
Curd, amount of, in butter, 41.

Daturic acid, 9.
Decroline, 33.
Demargarinated oil, 76.
Deodorisation of cocoanut oil, 34-36.
of fats, 34.
Digestibility of fats, oils, 3.
Diglycerides, 5.
Dika fat, 87.
Doeglic acid, 10.
Dripping, 2, 14, 65.
Dutch butter, 67.
Dyes, azo, 71.

Earth-nut oil, 18, 77, 108.
Elaidin test, 64, 79.
Eleomargaric acid, 12.
Eleostearic acid, 12.
Erucic acid, 10.

Fat as food, 1.
Fat, butter, 39-40.
Dika, 87.
goose, 6.
Illipé, 87.
Mkani, 87.
Tankawang, 87.
turkey, 6.
Fats, chocolate, 84-88.
constitution of, 1, 3.
deodorisation of, 34.
other vegetable, 86.
treatment of rancid, 36-38.
Fatty acids, volatile, 8, 10.
Fendler’s patent, 71.
Ficocerylic acid, 9.
Filtration, methods of, 25.
Flare lard, 60.
Flavouring, artificial, in margarine, 71-72.
Fluorides, 128.
Food, fat as, 1.
value, 3.
Foots, 27, 80.
Formulæ for margarine, 69-70.
(U.S.A.) Cheap Grade, 70.
High Grade, 70.
Medium High Grade, 70.
Free fatty acids, 91.
French salad oil, 79.
oil trade, 142.
Fuller’s earth, bleaching with, 30.

Gaboon fat, 87.
Gingelly oil, 79.
Glycerides, 3, 4.
Goose fat, 6.
Grades, commercial, of lard, 58-59.
Grease, brown, 58.
pig’s foot, 58.
white, 58.
yellow, 58.
Guts, 58.

Halphen’s test, 107.
Hehner value, 49, 118.
Huiles d’enfer, 75.
tournantes, 75.
Hyænic acid, 10.
Hydraldite C., 33.
Hydrosulphites, bleaching with, 33.
Hypogæic acid, 10.
Hyposulphites, bleaching with, 33.

Illipé butter, 87.
fat, 87.
Iodine value, 94.
of lard, 63, 64.
Irish butter, 52.
Isolinolenic acid, 12.
Isovaleric acid, 9.
Isovalerin, 6.

Jecoric acid, 12.

Keeping properties of butter, 42-44.

=Lard=, 15, 56.
acidity of, 61-62.
amount of water in, 62-63.
analysis of, 61.
choice (steam), 58.
commercial grades, 58-59.
composition of, 59.
crystals, 59-60.
examination of, 130.
flare, 60.
guts, 58.
influence of food on, 60-61.
iodine value, 63-64.
leaf, 58, 60.
neutral, 58.
oil, 15, 64.
prime, 58.
pure, 58.
rendering of, 56-58.
water in, 62.
Lauric acid, 9.
Laurin, 6, 7.
Lignoceric acid, 9.
Linde’s process, 24.
Linolenic acid, 9, 12.
Linolic acid, 9, 12.

Mafura tallow, 87.
Mahua butter, 87.
Maize oil, 16, 83-84.
analyses of, 84.
Malabar tallow, 87.
Margaric acid, 67.
=Margarine=, 3, 14, 65-66.
analyses of, 129.
artificial flavouring, 71-72.
colouring matter, 71.
composition of, 70.
English formula, 70.
formulæ for, 69-70.
Cheap Grade, 70.
High Grade, 70.
Medium High Grade, 70.
manufacture of, 66.
modern process, 68-69.
Margosa oil, 21.
Maumené test, 103.
Mège-Mouries process, 65-68.
Melissic acid, 10.
Methods of filtration, 25.
Milk-blended butter, 41.
Mixed glyceride, 5.
Mkani fat, 87.
Modern process margarine, 68-69.
Monoglycerides, 5.
Moringic acid, 10.
Mowrah-seed oil, 21.
Myristic acid, 9.
Myristin, 6, 7.

Nagel’s process, 37.
Neutral lard, 56, 68-69.
Nut butter, 72.
salad oils, 77.

=Oil=—
Arachis, 18, 77-78.
Butter, 16, 45.
Ceylon, 16.
Cochin, 16.
Cocoanut, 15.
Corn, 83, 84.
Cotton seed, 16, 80-82.
Demargarinated, 76.
Earth-nut, 18.
French salad, 79.
Gingelly, 79.
Lard, 15, 64.
Maize, 16, 83-84.
Margosa, 21.
Mowrah-seed, 21.
Nut salad, 77.
Olive, 17, 74-77.
Palm, 20, 72.
kernel, 18.
nut, 18.
Peanut, 18.
Poppy, 83.
Sesame, 18, 79-80.
Soya bean, 20.
Sunflower (seed), 19, 82-83.
Teel, 79.
of Theobroma, 19.
Virgin, 74, 76.
Winter cotton-seed, 81.
=Oils=—
bleaching of, 29.
constitution of, 1, 3.
pyrene, 75.
salad, 74-88.
semi-drying, 79, 81.
sulphocarbon, 75.
summer, 25, 80.
winter, 25, 76.
Oleic acid, 9, 10.
Olein, 6, 8.
Oleomargarine, 66, 67, 68, 70.
Oleo oil, 67, 69, 70.
Oleo-refractometer, 64.
Oleo-stearin, 69.
Olive oil, 17, 74-77, 106.
Organic peroxides, bleaching with, 33.
Ozonair apparatus, 32.
Ozone, bleaching with, 32.

Palm oil, 20, 72.
kernel oil, 18.
analyses of, 86.
stearin, 85, 86.
Palm-nut oil, 18.
stearin, 85.
Palmitic acid, 9.
Palmitin, 6, 7.
Peanut oil, 18, 77, 108.
Peroxides, bleaching with organic, 33.
Per-salts, 33.
Physetoleic acid, 10.
Physical characteristics of butter, 47.
methods of refining, 23.
Physiological considerations, 2.
Phytosteryl (acetate) test, 64, 82, 101.
Pig’s foot grease, 58.
Piney tallow, 87.
Pisangcerylic acid, 10.
Polenské’s test, 113.
Poppy oil, 83.
Premier jus, 14, 30, 68.
Preservatives in butter, 46, 47.
Prime steam lard, 58.
“Process” butter, 44-46.
Linde’s, 24.
Mège-Mouries, 65-68.
Nagel’s, 37.
Psyllostearylic acid, 10.
Pyrene oils, 75.

Rancid fats, treatment of, 36, 37, 38.
Rancidity in oils, 36.
of butter, 44.
Rapic acid, 10.
Raw materials, 14.
Refining with alkaline earths, 28.
caustic soda, 26.
sodium carbonate, 28.
silicate, 28.
of oils, 23.
Refractive index, 98.
Refractometer, butyro, 48.
Refractometric examination of butter, 48.
Reichert value, 49-50.
Reichert-Meissl value, 50-52.
process, 111.
Removal of stearin, 25.
Rendering of lard, 56-58.
Renovated butter, 44-46.
Ricinoleic acid, 9, 12.
Ricinolein, 6.
Rongalite C., 33.

Salad oils, 74-88.
Salt, amount of, in butter, 41.
oils, 121.
Saponification value, 92.
Semi-drying oils, 79, 81.
Sesame oil, 18, 79, 80.
Sesamin, 79.
Sesamol, 79.
Shea butter, 21, 87.
Sodium bisulphite, bleaching with, 33.
carbonate, refining with, 28.
silicate, refining with, 28.
Solidification point, 96.
Solubility of butter, 47.
Sorting tests, 48.
Soya bean oil, 20.
Spanish oil trade, 140.
Specific gravity, 90.
Statistics of oil trade, 137.
Steam lard, choice, 58.
Stearic acid, 9.
Stearin, 6, 8, 25, 76, 77, 79, 86.
cotton-seed, 17.
removal of, 25.
Stearins, cocoanut oil, 85, 86.
palm-kernel oil, 85, 86.
Suet, 14.
Sulphocarbon oils, 75.
Summer oils, 25, 80.
Sunflower(-seed) oil, 19, 82-83.

Tallow, 14.
Borneo, 87.
Mafura, 87.
Malabar, 87.
Piney, 87.
unrendered, 15.
Tankawang fat, 87.
Tariric acid, 12.
Teel oil, 79.
Telfairic acid, 12.
Test, elaidin, 64, 79.
phytosteryl, 64.
Valenta’s, 48.
Tests, sorting, 48.
Theobroma oil, 19.
Theobromic acid, 10.
Tiglic acid, 10.
Treatment of rancid fats, 36, 37, 38.
Triglycerides, 5, 6.
Turkey fat, 6.

Unrendered tallow, 15.
Unsaponifiable matter, 99.

Valenta’s test, 48, 102.
Value, food, 3.
Hehner, 49.
iodine, of lard, 63, 64.
Reichert, 49, 50.
Reichert-Meissl, 50-52.
Values, barium, 55.
Values, cadmium, 55.
Vegetable butter, 16, 72.
fats, other, 86.
Virgin oil, 74, 76.
Volatile fatty acids, 10.

Water, amount of, in butter, 41.
lard, 62, 63.
Watts’ bichromate process of bleaching, 31.
White grease, 58.
Winter cotton-seed oil, 81.
Winter oils, 25, 76.

Yellow grease, 58.

_Printed by_ MORRISON & GIBB LIMITED, _Edinburgh_

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