CHAPTER V 
THE FERMENTS AND FERMENTATIONS OF MILK, 
AND THEIR CONTROL 
MiLK, when it is first drawn, is a limpid fiuid 
with a slight odor, mildly sweetish taste, and faint 
alkaline reaction. In fact, milk often shows the 
amphoteric reaction; that is, it will give the acid 
reaction with blue litmus paper and the alkaline 
reaction with red. Almost immediately after it is 
drawn, milk begins to undergo a change, and within 
a short time will show a distinct acid reaction. 
The degree of acidity increases with the age of the 
milk. Soon changes begin in the other milk con- 
stituents, and in a comparatively short time, the de- 
composition is so great that the milk can no longer 
be used for food. The sugar is the first constit- 
uent of the milk to undergo change, afterwards 
the albuminoids are attacked, and lastly the fats. 
These changes are not due to any instability of the 
organic compounds in the milk, but to the effect 
of various vegetable germs that gain access to the 
milk after it is secreted, and, living and growing 
in the milk, bring about the changes mentioned. 
These changes are called fermentations, and _ the 
agents that bring them about ferments. Milk con- 
taining no germs of fermentation, or milk from 
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