87.20 percent average.
3.70 percent average.
9.10 percent average.
3.50 percent average.
4.90 percent average.
.70 percent average.
b. Water (Liquid). The 87.20 percent of milk that is liquid serves to hold the
other constituents of milk in solution, suspension, or emulsion.
c. Milkfat. There are two general types of milkfat or butterfat: true milkfat and
(1) True milkfat. True milkfat is composed of fatty acids and glycerols. It is
present in milk as an oil-in-water emulsion. The process whereby milkfat forms a cream
line is threefold. It is caused by the attraction of the fat globules to each other,
agglutination, and gravity.
(2) Fat-associated substances. The fat-associated substances are
phospholipids, cholesterol, carotene, vitamin A, and vitamin D.
d. Solids-Not-Fat. The solids-not-fat include the following constituents:
(1) Lactose. Lactose is a sugar found only in milk, and it provides the
characteristic flavor in milk. It is only one-fourth as sweet as sucrose (table sugar).
(2) Protein. Proteins in milk can be separated into casein protein and whey
protein. The casein protein is found only in milk. It is considered a complete protein
because it contains all the known, essential amino acids that are necessary for growth
and proper maintenance of the body.
(3) Minerals. Milk contains a great variety of minerals. The two most
important are calcium and phosphorus, which are present in the proper ratio (3 to 1) for
bone growth. Milk is deficient in iron, copper, and manganese, so one may develop
anemia if milk is the only food item in the diet.
e. The Effects of the Separation Process.
(1) Cream and skim milk. When unhomogenized milk stands for a few hours,
it separates into cream and skim milk.
(a) Cream contains most of the milkfat or butterfat and a small amount of