BACTERIA IN CHEESE 259 



are some instances where they may be very useful. In the or- 

 dinary working of a cheese factory it is hardly possible to use 

 the tests for the milk of any particular day, for it is impractical 

 to wait long enough to test the different samples of milk before 

 they are mixed together in a general curdling vat. But the 

 tests may be very useful in detecting whether the milk from 

 any one farm is constantly "off," so as to be a danger to the 

 general supply. For tracing the source of trouble the tests may 

 thus be of great value. 



The cheese maker should constantly bear in mind the danger 

 of contamination of his milk. Sometimes "off" flavors in 

 cheeses have been traced to bacteria in the dairy water supply. 

 Old barrels of souring whey are a source of trouble. The 

 practice of soaking rennet in sour whey to extract the rennet 

 material is sometimes common, but it is a bad practice, for such 

 a mixture furnishes a most excellent medium for bacteria 

 growth, and troublesome yeasts and bacteria have been traced 

 to such a source. Dirty cans sent back to the farm without 

 sterilization, slovenly methods in the barn, and, in short, all of 

 the sources of bacterial contamination previously mentioned are 

 very likely to trouble the cheese maker as much, if not more, 

 than any others connected with the dairy industry. 



