PART IV.
MILK AND MILK PRODUCTS AND OLEOMARGARINE.
MILK.
Limitation of Name.—By the term "milk," unless qualified in some way, is meant a lacteal secretion of the healthy cow, free of colostrum and of standard quality. If the milk of other mammals is meant the name of the class of animal is used in connection with the term, such as ewe's milk, goat's milk, etc. Milk is one of the most important articles of commerce and, by reason of its composition, high nutritive character, and easy digestibility, it is not only the natural food of infants but a most important food for children and adults. It is also an indispensible food in many, if not most, cases of disease where nutrition is impaired. In some cases life may often be sustained over a critical period by the use of milk as a food where other forms of food would fail of digestion and prove injurious instead of beneficial.
The United States standard for milk is found in Appendix A.
Average Composition of Milk.—Perhaps there is no food substance which has been subjected to so many and such severe analytical tests as milk. Hundreds of thousands of analyses have been made in all civilized countries, not only of the milk of the individual cow but of herds of greater or less size.
There is a great variation in the composition of milk in different breeds of cattle and also in different individuals of the same breed. For instance, the Holstein breed of cattle affords a milk with a very low content of fat, sometimes as low as 3.25 percent, and in individual cases lower. On the other hand the Jersey breed of cattle affords a milk of a very high content of fat, sometimes reaching as high as 6 percent, and in individual cases very much higher. The content of the nitrogenous element in milk is more stable than that of fat and the common content of casein in milk ranges from 2-1/2 to 3-1/4 percent. The sugar in the milk is usually the complementary substance with the fat, diminishing in relative proportions as the fat increases and vice versa. The average content of sugar in cow's milk is approximately 4 percent. The content of mineral substances in milk is also quite constant, being about 0.70. The ash contains the phosphoric acid which is one of the essential food components of milk. A milk of fair average quality contains 12 percent of solids and 88 percent of water. This is an expression for milk during the
