Dairying comprises two occupations, — dairy husbandry, or the producing of milk ; and dairy industry, or the marketing and manufacturing of milk and milk products. This chapter is designed to compass chiefly some phases of the latter subject.

Composition of Milk

Composition of cow's milk

Fat in milk is in the form of minute globules having a diameter of 1/15000 to 1/2500 of an inch. These float in the milk, forming an emulsion. When highly magnified, these fat globules may be easily seen. In any milk, many different sizes of globules are found, but the average size of globules in Jersey and Guernsey milk is much larger than the average size of globules in the milk given by other breeds. As the specific gravity of the fat is .93 and the specific gravity of the remainder of the milk is about 1.04, the fat globules always tend to rise. They are more or less entangled by other constituents of the milk, and great numbers of the smallest sized globules fail to reach the top, or the cream layer (Pearson).

Milk-fat is a mixture of several different fats which are combinations

COMPOSITION OF MILK of glycerine and fatty acids. The principal fats and their proportion in milk-fat are as follows: —

Per Cent

Palmitin......................40

Olein.......................34

Myristin......................10

Butyrin......................6

A few others vary from 1 to 3 per cent each.

Butyrin is the characteristic butter-fat, and is absent from butter substitutes, such as oleomargarine. The melting-point of milk-fat is about 92° F. (Pearson).

Average composition of milk of various kinds (U. S. Dept. Agric.)

Average composition of typical cow's milk (Conn. Sta.)

MILK AND MILK PRODUCTS: DAIRY FARMS

The milk of different breeds.

The analyses of large numbers of samples of milk given by different breeds have been made by the New York Agricultural Experiment Station, and the averages of fat for the different breeds are : —

Per Cent

Holstein-Friesian...................    3.4

Ayrshire......................    3.6

Shorthorn.....................    4.4

Devon......................    4.6

Guernsey.....................    5.3

Jersey......................    5.6

Composition of milk solids from six breeds of cows (Van Slyke)

Ash in cow's milk and its products (Simon)

Whole milk . . ....................0074

Skim milk......................0074

Cream .......................0061

Buttermilk......................0067

Whey........................0065

Mineral constituents in milk (Abderhalden)