composed. In the processes of butter and cheese making,
these fermentation changes are controlled so as to develop the flavor
and secure the best grades of butter and cheese.

108. Use of Preservatives in Milk.--In order to check fermentation,
boric acid, formalin, and other preservatives have been proposed.
Physiologists object to their use because the quantity required to
prevent fermentation is often sufficient to have a medicinal effect.
The tendency is to use excessive amounts, which may interfere with
normal digestion of the food. Milk that is cared for under the most
sanitary conditions has a higher dietetic value and is much to be
preferred to that which has been kept sweet by the use of preservatives.

109. Condensed Milk is prepared by evaporating milk in vacuum pans
until it is reduced about one fourth in bulk, when it is sealed in cans,
and it will then keep sweet for a long time. Occasionally some cane
sugar is added to the evaporated product. When diluted, evaporated milk
has much the same composition as whole milk. When a can of condensed
milk has been opened, the same care should be exercised to prevent
fermentation as if it were fresh milk.

110. Skim Milk differs in composition from whole milk in fat content.
When the fat is removed by the separator, there is often left less than
one tenth of a per cent. Skim milk has a much higher nutritive value
than is generally conceded, and wherever it can be procured at a
reasonable price it should be used in the dietary as a source of
protein.

111. Cream ranges in fat content from 15 to 35 per cent. It is
generally preferred to whole milk, although it is not as well balanced a
food, because it is deficient in protein. Cream should contain at least
25 per cent of fat.

112. Buttermilk is the product left after removal of the fat from
cream by churning. It has about the same amount of nutrients as skim
milk. The casein is in a slightly modified form due to the development
of lactic acid during the ripening of the cream, and on this account
buttermilk is more easily digested and assimilated by many individuals
than milk in other forms. The development of the acid generally reduces
the number of species of other than the lactic organisms, and these are
increased.

113. Goat's Milk is somewhat richer in solids than cow's milk,
containing about one per cent more proteids, a little more fat, and less
sugar. When used as a substitute for human or cow's milk, it