=507. Substitutes and Adulterants of Butter.=—In this country, butter
is never adulterated with cocoa or sesame oil, as is sometimes the case
in other lands. The common substitute for butter here is oleomargarin,
and the most common butter adulterant, neutral lard. The methods of
analyses, by means of which these bodies can be identified, have
already been sufficiently described. By the use of certain digestive
ferments and other bodies, butter may be made to hold an excessive
quantity of casein, sugar and water in the form of a somewhat permanent
emulsion.[508] This form of adulteration is revealed at once on melting
the sample.
=508. Furfurol Reaction with Sesame Oil.=—Olive oil and sometimes
butter are mixed with the cheaper body, sesame oil. The latter is
detected with certainty, from the red coloration it gives when mixed
with furfurol and hydrochloric acid. Instead of furfurol, some body
yielding it when subjected to the action of hydrochloric acid, _viz._,
sucrose or a pentose sugar, may be used. It has been found by Wauters,
however, that an alcoholic solution of two grams of furfuraldehyd in
100 cubic centimeters of alcohol is the best reagent. One-tenth of a
cubic centimeter of this reagent is used for each test.[509]
The test is made as follows: The quantity of the furfuraldehyd solution
mentioned above is mixed with ten cubic centimeters of hydrochloric
acid, and there are added, without mixing, an equal volume of the
suspected oil. On standing, a red coloration is produced at the zone of
separation of the two liquids. If the oil be sesame, the coloration is
produced instantly. As little as one per cent of sesame in a mixed oil
will show the color in two minutes. The manipulation is also varied by
shaking together the reagents and the melted butter. Turmeric, which
is sometimes used in coloring butter, also gives the rose-red color
when treated with hydrochloric acid, but turmeric supplies its own
furfuraldehyd. It is easy to distinguish therefore the coloration due
to sesame oil, which is developed only when furfuraldehyd is present,
from that due to the turmeric, which is produced without the aid of the
special reagent.
=509. Butter Colors.=—Where cows are deprived of green food and root
crops, such as carrots, and kept on a poorly balanced ration, the
butter made from their milk may be almost colorless. To remedy this
defect it is quite a common practice to color the product artificially.
Almost the sole coloring matter used in this country is anatto.[510]
Other coloring matters which are occasionally employed are turmeric,
saffron, marigold leaves, yellow wood (_Chlorophora tinctoria_), carrot
juice, chrome yellow (lead chromate) and dinitrocresol.
The use of small quantities of anatto, turmeric or saffron is
unobjectionable, from a sanitary point of view, but this is not the
case with such a substance as lead chromate. The detection of anatto or
saffron in butter may be accomplished by the method of Cornwall.[511]
About five grams of the warm filtered fat are dissolved in about fifty
cubic centimeters of ordinary ether, in a wide tube, and the solution
is vigorously shaken for from ten to fifteen seconds, with from twelve
to fifteen cubic centimeters of a very dilute solution of caustic
potash or soda in water, only alkaline enough to give a distinct
reaction with turmeric paper, and to remain alkaline after separating
from the ethereal fat solution. The corked tube is set aside, and in
a few hours, at most, the greater part of the aqueous solution, now
colored more or less yellow by the anatto, can be drawn from beneath
the ether with a pipette or by a stopcock below, in a sufficiently
clear state to be evaporated to dryness and tested in the usual way
with a drop of concentrated sulfuric acid.
Sometimes it is well to further purify the aqueous solution by shaking
it with some fresh ether before evaporating it, and any fat globules
that may float on its surface during evaporation should be removed by
touching them with a slip of filter paper; but the solution should not
be filtered, because the filter paper may retain much of the coloring
matter.
The dry yellow or slightly orange residue turns blue or violet blue
with sulfuric acid, then quickly green, and finally brownish or
somewhat violet this final change being variable, according to the
purity of the extract.
Saffron can be extracted in the same way; it differs from anatto very
decidedly, the most important difference being in the absence of the
green coloration.
Genuine butter, free from foreign coloring matter, imparts at most a
very pale yellow color to the alkaline solution; but it is important
to note that a mere green coloration of the dry residue on addition
of sulfuric acid is not a certain indication of anatto (as some books
state) because the writer has thus obtained from genuine butter,
free from foreign coloring matter, a dirty green coloration, but not
preceded by any blue or violet-blue tint.
Blank tests should be made with the ether.
Turmeric is easily identified by the brownish to reddish stratum that
forms between the ethereal fat solution and the alkaline solution
before they are intimately mixed. It may be even better recognized by
carefully bringing a feebly alkaline solution of ammonia in alcohol
beneath the ethereal fat solution with a pipette, and gently agitating
the two, so as to mix them partially.
Another method of separating artificial coloring matter has been
proposed by Martin.[512]
A method of determining the relative amount of butter color has been
worked out by Babcock.[513]