substances, such as vinegar and some distilled liquors. To detect it
two test tubes or small bottles of about equal size and shape should
be employed and an equal amount (2 or 3 tablespoonfuls or more) of the
suspected sample placed in each. To one of these bottles is added a
teaspoonful of fuller’s earth, the sample shaken vigorously for 2 or
3 minutes, and then filtered through filter paper, the first portion
of the filtered liquid being returned to the filter paper and the
sample finally collected into the test tube or bottle in which it
was originally placed, or a similar one. The filtered liquid is now
compared with the untreated sample. If it is markedly lighter in color
it may be taken for granted that the color of the liquid is due to
caramel, which is largely removed by fuller’s earth. In applying this
test, however, it must be borne in mind that caramel occurs naturally
in malt vinegar, being formed in the preparation of the malt. It is
evident that the tests require practice and experience before they can
be successfully performed. The housewife can use them, but must repeat
them frequently in order to become proficient in their use.
«EXAMINATION OF CERTAIN CLASSES OF FOODS:»
«Canned Vegetables.»—These are relatively free from adulteration by
means of foreign substances. The different grades of products may with
care be readily detected by the general appearance of the sample. The
purchaser is, of course, at the disadvantage of not being able to see
the product until the can is opened. By a study of the different brands
available in the vicinity, however, he can readily select those which
are preferable. As stated in an earlier part of this article, canned
tomatoes sometimes contain an artificial coloring matter, which may be
detected as described.
Canned sweet corn is sometimes sweetened with saccharine, which may be
detected as described.
It is believed that, as a rule, canned vegetables are free from
preservatives, although some instances of chemical preservation have
recently been reported in North Dakota, and some imported {353}
tomatoes have been found to be artificially preserved. The presence of
copper, often used for the artificial greening of imported canned peas,
beans, spinach, etc., may be detected as described.
«Coffee.»—There are a number of simple tests for the presence of the
adulterants of ground coffee. These are called simple because they can
be performed without the facilities of the chemical laboratory, and by
one who has not had the experience and training of a chemist. It must
be understood that they require careful observation and study, and that
one must perform them repeatedly in order to obtain reliable results.
Before applying them to the examination of an unknown sample, samples
of known character should be secured and studied. Unground coffee may
be ground in the home and mixed with various kinds of adulterants,
which can also be secured separately. Thus the articles themselves in
known mixtures may be studied, and when the same results are obtained
with unknown samples they can be correctly interpreted. These tests are
well known in the laboratory and may be used in the home of the careful
housewife who has the time and perseverance to master them.
Physical Tests.—The difference between the genuine ground coffee and
the adulterated article can often be detected by simple inspection with
the naked eye. This is particularly true if the product be coarsely
crushed rather than finely ground. In such condition pure coffee has a
quite uniform appearance, whereas the mixtures of peas, beans, cereals,
chicory, etc., often disclose their heterogeneous nature to the careful
observer. This is particularly true if a magnifying glass be employed.
The different articles composing the mixture may then be separated by
the point of a pen-knife. The dark, gummy-looking chicory particles
stand out in strong contrast to the other substances used, and their
nature can be determined by one who is familiar with them by their
astringent taste.
The appearance of the coffee particles is also quite distinct from
that of many of the coffee substitutes employed. The coffee has a
dull surface, whereas some of its substitutes, especially leguminous
products, often present the appearance of having a polished surface.
After a careful inspection of the sample with the naked eye, or,
better, with a magnifying glass, a portion of it may be placed in a
small bottle half full of water and shaken. The bottle is then placed
on the table for a moment. Pure coffee contains a large amount of oil,
by reason of which the greater portion of the sample will float. All
coffee substitutes and some particles of coffee sink to the bottom
of the liquid. A fair idea of the purity of the sample can often be
determined by the proportion of the sample which floats or sinks.
Chicory contains a substance which dissolves in water, imparting a
brownish-red color. When the suspected sample is dropped into a glass
of water, the grains of chicory which it contains may be seen slowly
sinking to the bottom, leaving a train of a dark-brown colored liquid
behind them. This test appears to lead to more errors in the hands
of inexperienced operators than any other test here given. Wrong
conclusions may be avoided by working first with known samples of
coffee and chicory as suggested above.
Many coffee substitutes are now sold as such and are advertised as
more wholesome than coffee. Notwithstanding the claims that are made
for them, a few of them contain a considerable percentage of coffee.
This may be determined by shaking a teaspoonful in a bottle half full
of water, as described above. The bottle must be thoroughly shaken
so as to wet every particle of the sample. Few particles of coffee
substitutes will float.
Chemical Tests.—Coffee contains no starch, while all of the substances,
except chicory, used for its adulteration and in the preparation
of coffee substitutes contain a considerable amount of starch. The
presence of such substitutes may, therefore, be detected by applying
the test for starch. In making this test less than a quarter of a
teaspoonful of ground coffee should be used, or a portion of the
ordinary infusion prepared for the table may be employed after
dilution. The amount of water that should be added can only be
determined by experience.
«Condimental Sauces.»—Tomato catsup and other condimental sauces are
frequently preserved and colored artificially. The preservatives
employed are usually salicylic acid and benzoic acid or their sodium
salts. These products may be detected by the methods given.
Coal-tar colors are frequently employed with this class of goods,
especially with those of a reddish tint, like tomato catsup. They may
be detected by the methods given. {354}
«DAIRY PRODUCTS:»
«Butter.»—Methods are available which, with a little practice, may be
employed to distinguish between fresh butter, renovated or process
butter, and oleomargarine.
These methods are commonly used in food and dairy laboratories. They
give reliable results. At the same time considerable practice is
necessary before we can interpret correctly the results obtained. Some
process butters are on the market which can be distinguished from
fresh butter only with extreme difficulty. During the last few years
considerable progress has been made in the attempt to renovate butter
in such a way that it will appear like fresh butter in all respects. A
study must be made of these methods if we would obtain reliable results.
The “spoon” test has been suggested as a household test, and is
commonly used by analytical chemists for distinguishing fresh butter
from renovated butter and oleomargarine. A lump of butter, 2 or 3
times the size of a pea, is placed in a large spoon and heated over
an alcohol or Bunsen burner. If more convenient the spoon may be
held above the chimney of an ordinary kerosene lamp, or it may even
be held over an ordinary illuminating gas burner. If the sample in
question be fresh butter it will boil quietly, with the evolution of
many small bubbles throughout the mass which produce a large amount
of foam. Oleomargarine and process butter, on the other hand, sputter
and crackle, making a noise similar to that heard when a green stick
is placed in a fire. Another point of distinction is noted if a small
portion of the sample be placed in a small bottle and set in a vessel
of water sufficiently warm to melt the butter. The sample is kept
melted from half an hour to an hour, when it is examined. If renovated
butter or oleomargarine, the fat will be turbid, while if genuine fresh
butter the fat will almost certainly be entirely clear.
To manipulate what is known as the “Waterhouse” or “milk” test, about
2 ounces of sweet milk are placed in a wide-mouthed bottle, which is
set in a vessel of boiling water. When the milk is thoroughly heated, a
teaspoonful of butter is added, and the mixture stirred with a splinter
of wood until the fat is melted. The bottle is then placed in a dish
of ice water and the stirring continued until the fat solidifies. If
the sample be butter, either fresh or renovated, it will be solidified
in a granular condition and distributed through the milk in small
particles. If, on the other hand, the sample consist of oleomargarine
it solidifies practically in one piece and may be lifted by the stirrer
from the milk.
By these two tests, the first of which distinguishes fresh butter from
process or renovated butter and oleomargarine, and the second of which
distinguishes oleomargarine from either fresh butter or renovated
butter, the nature of the sample under examination may be determined.
«Milk.»—The oldest and simplest method of adulterating milk is by
dilution with water. This destroys the natural yellowish-white color
and produces a bluish tint, which is sometimes corrected by the
addition of a small amount of coloring matter.
Another form of adulteration is the removal of the cream and the
sale as whole milk of skimmed or partially skimmed milk. Again, the
difficulty experienced in the preservation of milk in warm weather has
led to the widespread use of chemical preservatives.
_Detection of Water._—If a lactometer or hydrometer, which can be
obtained of dealers in chemical apparatus, be available, the specific
gravity of milk will afford some clew as to whether the sample has
been adulterated by dilution with water. Whole milk has a specific
gravity between 1.027 and 1.033. The specific gravity of skimmed milk
is higher, and milk very rich in cream is sometimes lower than these
figures. It is understood, of course, that by specific gravity is meant
the weight of a substance with reference to the weight of an equal
volume of water. The specific gravity of water is 1. It is obvious that
if water be added to a milk with the specific gravity of 1.030, the
specific gravity of the mixture will be somewhat below those figures.
An indication by means of a hydrometer or lactometer below the figure
1.027 therefore indicates either that the sample in question is a very
rich milk or that it is a milk (perhaps normal, perhaps skimmed) that
has been watered. The difference in appearance and nature of these
two extremes is sufficiently obvious to make use of the lactometer or
hydrometer of value as a preliminary test of the purity of milk.
_Detection of Color._—As previously stated, when milk is diluted by
means of water the natural yellowish-white color is changed to a bluish
tint, which is sometimes corrected by the addition {355} of coloring
matter. Coal-tar colors are usually employed for this purpose. A
reaction for these colors is often obtained in the method given below
for the detection of formaldehyde. When strong hydrochloric acid is
added to the milk in approximately equal proportions before the mixture
is heated a pink tinge sometimes is evident if a coal-tar color has
been added.
_Detection of Formaldehyde._—Formaldehyde is the substance most
commonly used for preserving milk and is rarely, if ever, added to any
other food. Its use is inexcusable and especially objectionable in milk
served to infants and invalids.
To detect formaldehyde in milk 3 or 4 tablespoonfuls of the sample are
placed in a teacup with at least an equal amount of strong hydrochloric
acid and a piece of ferric alum about as large as a pinhead, the
liquids being mixed by a gentle rotary motion. The cup is then placed
in a vessel of boiling water, no further heat being applied, and left
for 5 minutes. At the end of this time, if formaldehyde be present, the
mixture will be distinctly purple. If too much heat is applied, a muddy
appearance is imparted to the contents of the cup.
_Caution._—Great care must be exercised in working with hydrochloric
acid, as it is strongly corrosive.
«Edible Oils.»—With the exception of cottonseed oil, the adulterants
ordinarily used with edible oils are of such a nature that the
experience of a chemist and the facilities of a chemical laboratory are
essential to their detection. There is, however, a simple test for the
detection of cottonseed oil, known as the Halphen test, which may be
readily applied.
Great care must be taken in the manipulation of this test, as one
of the reagents employed—carbon bisulphide—is very inflammable. The
chemicals employed in the preparation of the reagent used for this
test are not household articles. They may, however, be obtained in any
pharmacy. The mixture should be prepared by a druggist rather than by
an inexperienced person who desires to use it.
In order to perform the test 2 or 3 tablespoonfuls of this reagent are
mixed in a bottle with an equal volume of the suspected sample of oil
and heated in a vessel of boiling salt solution (prepared by dissolving
1 tablespoonful of salt in a pint of water) for 10 or 15 minutes. At
the end of that time, if even a small percentage of cottonseed oil be
present, the mixture will be of a distinct reddish color, and if the
sample consists largely or entirely of cottonseed oil, the color will
be deep red.
«Eggs.»—There is no better method for the testing of the freshness
of an egg than the familiar one of “candling,” which has long been
practiced by dealers. The room is darkened and the egg held between
the eye and a light; the presence of dark spots indicates that the egg
is not perfectly fresh, one that is fresh presenting a homogeneous,
translucent appearance. Moreover, there is found in the larger end of
a fresh egg, between the shell and the lining membrane, a small air
cell which, of course, is distinctly transparent. In an egg which is
not perfectly fresh this space is filled and hence presents the same
appearance as the rest of the egg.
It is now a matter of considerable importance to be able to distinguish
between fresh eggs and those that have been packed for a considerable
time. Until recently that was not a difficult matter. All of the
solutions that were formerly extensively used for that purpose gave
the shell a smooth, glistening appearance which is not found in the
fresh egg. This characteristic, however, is of less value now than
formerly, owing to the fact that packed eggs are usually preserved
in cold storage. There is now no means by which a fresh egg can be
distinguished from a packed egg without breaking it. Usually in eggs
that have been packed for a considerable time the white and yolk
slightly intermingle along the point of contact, and it is a difficult
matter to separate them. Packed eggs also have a tendency to adhere to
the shell on one side and when opened frequently have a musty odor.
«FLAVORING EXTRACTS.»
Although a large number of flavoring extracts are on the market,
vanilla and lemon extracts are used so much more commonly than other
flavors that a knowledge of their purity is of the greatest importance.
Only methods for the examination of those two products will be
considered.
«Vanilla Extract.»—Vanilla extract is made by extracting vanilla beans
with alcohol. It consists of an alcoholic solution of vanillin (the
characteristic flavoring matter of the vanilla bean) and several other
products, chiefly rosins, which, though present in but small amount and
having only a slight flavor in themselves, yet affect very materially
{356} the flavor of the product. Vanilla extract is sometimes
adulterated with the extract of the Tonka bean. This extract, to a
certain extent, resembles vanilla extract. The extract of the Tonka
bean, however, is far inferior to that of the vanilla bean. It has a
relatively penetrating, almost pungent odor, standing in sharp contrast
to the flavor of the vanilla extract. This odor is so different that
one who has given the matter some attention may readily distinguish the
two, and the quality of the vanilla extract may often be judged with a
fair degree of accuracy by means of the odor alone.
Another form of adulteration, and one that is now quite prevalent,
is the use of artificial vanillin in place of the extract of either
vanilla or Tonka beans. Artificial vanillin has, of course, the same
composition and characteristics as the natural vanillin of the vanilla
bean. Extracts made from it, however, are deficient in the rosins and
other products which are just as essential to the true vanilla, as is
vanillin itself. Since vanillin is thus obtained from another source so
readily, methods for the determination of the purity of vanilla extract
must depend upon the presence of other substances than vanillin.
_Detection of Caramel._—The coloring matter of vanilla extract is
due to substances naturally present in the vanilla bean and extracted
therefrom by alcohol. Artificial extracts made by dissolving artificial
vanillin in alcohol contain no color of themselves, and to supply it
caramel is commonly employed. Caramel may be detected in artificial
extracts by shaking and observing the color of the resulting foam after
a moment’s standing. The foam of pure extracts is colorless. If caramel
is present a color persists at the points of contact between the
bubbles until the last bubble has disappeared. The test with fuller’s
earth given for caramel in vinegar is also very satisfactory, but of
course requires the loss of the sample used for the test.
_Examination of the Rosin._—If pure vanilla extract be evaporated to
about one-third its volume the rosins become insoluble and settle to
the bottom of the dish. Artificial extracts remain clear under the
same conditions. In examining vanilla extract the character of these
rosins is studied. For this purpose a dish containing about an ounce
of the extract is placed on a teakettle or other vessel of boiling
water until the liquid evaporates to about one-third or less of its
volume. Owing to the evaporation of the alcohol the rosins will then be
insoluble. Water may be added to restore the liquid to approximately
its original volume. The rosin will then separate out as a brown
flocculent precipitate. A few drops of hydrochloric acid may be added
and the liquid stirred and the insoluble matter allowed to settle. It
is then filtered and the rosin on the filter paper washed with water.
The rosin is then dissolved in a little alcohol, and to 1 portion of
this solution is added a small particle of ferric alum, and to another
portion a few drops of hydrochloric acid, If the rosin be that of the
vanilla bean, neither ferric alum nor hydrochloric acid will produce
more than a slight change of color. With rosins from most other
sources, however, one or both of these substances yield a distinct
color change.
For filtering, a piece of filter paper should be folded once through
the middle and again at right angles to the first fold. It may now be
opened with one fold on one side and three on the other and fitted
into a glass funnel. When the paper is folded in this manner the
precipitated rosins may be readily washed with water. When the washing
is completed the rosins may be dissolved by pouring alcohol through the
filter. This work with the rosins will require some practice before it
can be successfully performed. It is of considerable value, however, in
judging of the purity of vanilla extract.
«Lemon Extract.»—By lemon extract is understood a solution of lemon
oil in strong alcohol. In order to contain as much lemon oil as
is supposed to be found in high-grade extracts the alcohol should
constitute about 80 per cent of the sample. The alcohol is therefore
the most valuable constituent of lemon extract, and manufacturers who
turn out a low-grade product usually do so because of their economy
of alcohol rather than of lemon oil. Owing to the fact that lemon
extract is practically a saturated solution of oil of lemon in strong
alcohol the sample may be examined by simple dilution with water. A
teaspoonful of the oil in question may be placed in the bottom of an
ordinary glass tumbler and 2 or 3 teaspoonfuls of water added. If the
sample in question be real lemon extract the lemon oil should be thrown
out of solution by reason of its insolubility in the alcohol after
its dilution with water. The result is at first a marked turbidity
and later the separation of the oil of lemon on the top {357} of
the aqueous liquid. If the sample remains perfectly clear after the
addition of water, or if a marked turbidity is not produced, it is a
low-grade product and contains very little, if any, oil of lemon.
«Fruit Products.»—Adulteration of fruit products is practically
confined to jellies and jams. Contrary to the general belief, gelatin
is never used in making fruit jelly. In the manufacture of the very
cheapest grade of jellies starch is sometimes employed. Jellies
containing starch, however, are so crude in their appearance that the
most superficial inspection is sufficient to demonstrate that they are
not pure fruit jellies. From their appearance no one would think it
worth while to examine them to determine their purity.
Natural fruit jellies become liquid on being warmed. A spoonful
dissolves readily in warm water, although considerable time is
required with those that are especially firm. The small fruits contain
practically no starch, as apples do, and the presence of starch in a
jelly indicates that some apple juice has probably been used in its
preparation.
_Detection of Starch._—Dissolve a teaspoonful of jelly in a half
teacupful of hot water, heat to boiling and add, drop by drop,
while stirring with a teaspoon, a solution of potassium permanganate
until the solution is almost colorless. Then allow the solution to
cool and test for starch with tincture of iodine, as directed later.
Artificially colored jellies are sometimes not decolorized by potassium
permanganate. Even without decolorizing, however, the blue color can
usually be seen.
_Detection of Glucose._—For the detection of glucose, a teaspoonful
of the jelly may be dissolved in a glass tumbler or bottle in 2 or 3
tablespoonfuls of water. The vessel in which the jelly is dissolved may
be placed in hot water if necessary to hasten the solution. In case a
jam or marmalade is being examined, the mixture is filtered to separate
the insoluble matter. The solution is allowed to cool, and an equal
volume or a little more of strong alcohol is added. If the sample is
a pure fruit product the addition of alcohol causes no precipitation,
except that a very slight amount of proteid bodies is thrown down. If
glucose has been employed in its manufacture, however, a dense white
precipitate separates and, after a time, settles to the bottom of the
liquid.
_Detection of Foreign Seeds._—In addition to the forms of adulteration
to which jellies are subject, jams are sometimes manufactured from
the exhausted fruit pulp left after removing the juice for making
jelly. When this is done residues from different fruits are sometimes
mixed. Exhausted raspberry or blackberry pulp may be used in making
“strawberry” jam and _vice versa_. Some instances are reported of
various small seeds, such as timothy, clover, and alfalfa seed, having
been used with jams made from seedless pulp.
With the aid of a small magnifying glass such forms of adulteration may
be detected, the observer familiarizing himself with the seeds of the
ordinary fruits.
_Detection of Preservatives and Colors._—With jellies and jams
salicylic and benzoic acids are sometimes employed. They may be
detected by the methods given.
Artificial colors, usually coal-tar derivatives, are sometimes used and
may be detected as described.