26 MARKET DAIRYING 
be due to strippers’ milk and to certain classes of feeds 
and weeds, but most frequently to bacteria. This class 
of bacteria has not yet been studied very thoroughly but 
we know a great deal about it in a practical way. In 
milk and cream in which the action of the lactic acid 
germs has been suppressed by low temperatures, bitter- 
ness due to the development of the bitter fermentation is 
almost certain to be noticeable. When the temperature 
is such as to cause a rapid development of the lactic 
fermentation, the bitter fermentation is rarely, if ever, 
present. It is quite evident from this that the bitter 
organisms are capable of growing at much lower tem- 
peratures than the lactic and that so long as the latter 
are rapidly growing the bitter fermentation is held in 
check. 
This teaches us that it is not safe to ripen cream below 
60° F. The author has found that cream quickly ripened 
and then held at a temperature of 45° for twenty-four 
hours would show no tendency toward bitterness, while 
the same cream held sweet at 45° for twenty-four hours 
and then ripened would develop a bitter flavor. This 
indicates that the lactic acid is unfavorable to the develop- 
ment of the bitter fermentation. 
The bitter germs produce spores capable of resisting 
the boiling temperature. This accounts for the bitter 
taste that often develops in boiled milk. 
2. SLIMY OR ROPY FERMENTATION. 
This is not a common fermentation and_ rarely 
causes trouble where cleanliness is practiced in the dairy. 
The bacteria that produce it are usually found in impure 
water, dust and dung. These germs are antagonistic to 
