TABLE I
| Composition of Milk | ||||||
| Water Per Cent | Fat Per Cent | Casein Per Cent | Sugar Per Cent | Albumin Per Cent | Ash Per Cent | |
High | 88.90 | 5.50 | 3.00 | 5.00 | .72 | .73 |
| Low | 85.05 | 3.00 | 2.10 | 4.60 | .70 | .70 |
| Average | 87.47 | 3.80 | 2.50 | 4.80 | .71 | .71 |
8. Factors causing variation in composition.—The composition of cow's milk varies according to several factors. The composition of the milk of different breeds differs to such a degree that whole series of factories are found with lower or higher figures than these averages on account of dominant presence of particular kinds of cattle.
The following table shows the usual effect of breed on fat and total solids of milk:
TABLE II
| The Usual Effect of Breed of Cows on Fat and TotalSolids of Milk | ||
| Breed of Cows | Averages | |
| Fat Per Cent | Total Solids Per Cent | |
Jersey | 5.62 | 14.74 |
| Guernsey | 5.34 | 14.70 |
| Shorthorn | 4.17 | 13.41 |
| Ayrshire | 3.61 | 12.72 |
| Holstein-Friesian | 3.30 | 11.89 |
The figures[1] in Tables I and II are compiled and averaged from a large number of analyses made at different agricultural experiment stations.
This variation not only affects the fat, but all constituents of the milk. While there is a difference in the composition of the milk from cows of different breeds, there is almost as wide variation in the composition of the milk from single cows[2] of the same breed. With the same cow the stage of lactation causes a wide variation in the composition of the milk.[3] As the period of lactation advances, the milk increases in percentage of fat and other solids.
9. Milk constituents.—From the standpoint of the cheese-maker, the significant constituents of milk are water, fat, casein, milk-sugar, albumin, ash and enzymes. These will be discussed separately.
10. Water.—The retention of the solids and the elimination of the water are among the chief considerations in cheese-making. Water forms 84 to 89 per cent of milk. Cheese-making calls for the reduction of this percentage to that typical of the particular variety of cheese desired with the least possible loss of milk solids. This final percentage varies from 30 to 70 per cent with the variety of cheese. The water has two uses in the cheese: (1) It imparts smoothness and mellowness to the body of the cheese; (2) it furnishes suitable conditions for the action of the ripening agents. To some extent the water may supplement or even replace fat in its effect on the texture of the cheese. If the cheese is properly made, the water present is in such combination as to give no suggestion of a wet or "leaky" product.