In considering the food substances of milk, it will be well to note also
that they vary according to the breed, feeding, and individual
characteristics of the cow. Jerseys and Guernseys give milk rich in fat
and total solids, and while Holstein cows give a greater quantity of
milk, such milk has a smaller proportion of fat and total solids. As a
rule, though, the composition of milk may be considered as approximately
3.3 per cent. protein, 4 per cent. fat, 5 per cent. carbohydrate, and
.7 per cent. mineral matter, making a total of 13 per cent. This
indicates the quantity of actual food material in milk, the remainder,
or 87 per cent., being water.
8. PROTEIN IN MILK.--Because of the double usefulness of protein--to
serve as fuel and to make and repair muscular tissue--this element is
regarded as an important ingredient of milk. The protein in milk is
called _casein_. The opaque whiteness of milk is largely due to the
presence of this substance. As long as milk remains sweet, the lime
salts it contains hold this casein in solution; but when it sours, the
salts are made soluble and the casein thickens, or coagulates. In
addition to casein, milk contains a small amount of protein in the form
of _albumin_. This substance, upon being heated, coagulates and causes
the formation of the skin that is always found on the top of milk that
has been heated. The skin thus formed contains everything that is found
in milk, because, as it forms, casein is dried with it and sugar and
fat, too, are caught and held there.
Pages:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25