generally
needs to be slightly diluted, depending, however, upon the composition
of the individual sample.

114. Koumiss is a fermented beverage made from milk by the use of
yeast to secure alcoholic fermentation. Koumiss contains about one per
cent each of lactic acid and alcohol, and the casein and other nutrients
are somewhat modified by the fermentation changes. Koumiss is generally
considered a non-alcoholic beverage possessing both food and dietetic
value.

115. Prepared Milks.--Various preparations are made to resemble milk
in general composition. These are mechanical mixtures of sugar, fats,
and proteids. Milk sugar, casein, or malted proteids are generally the
materials employed in their preparation. Often the dried and pulverized
solids of skim milk are used. Many of the prepared milks are deficient
in fat. While they are not equal to cow's milk, their use is often made
necessary from force of circumstances.

116. Human Milk is not as rich in solid matter as cow's milk. It
contains about the same amount of fat, one per cent more sugar, and one
per cent less proteids. In human milk nearly one half of the protein is
in the form of albumins, while in cow's milk there is about one fifth in
this form. The fat globules are much smaller than those of cow's milk.
In infant feeding it is often necessary to modify cow's milk by the
addition of water, cream, and milk sugar, so as to make it more nearly
resemble in composition human milk.

[Illustration: FIG. 25.--APPARATUS USED IN TESTING MILK.

1, pipette; 2, lactometer; 3, acid measure; 4, centrifuge; 5, test
bottle.]

117. Adulteration of Milk.--Milk is not as extensively adulterated as
it was before the passage and enforcement of the numerous state and
municipal laws regulating its inspection and sale. The most frequent
forms of adulteration are addition of water and removal of cream. These
are readily detected from the specific gravity and fat content of the
milk. The specific gravity of milk is determined by means of the
lactometer, an instrument which sinks to a definite point in pure milk.
In watered milk it sinks to greater depth, depending upon the amount of
water added. The fat content of milk is readily and accurately
determined by the Babcock test, in which the fat is separated by
centrifugal action. For the detection of adulterated milk the student
is referred to Chapter VI, "Chemistry of Dairying," by Snyder.

BUTTER

118. Composition.--Butter