THE RELATION OF MICROORGANISMS TO CHEESE 



423 



Bad. lactis acidi to the milk, the proportion of desirable bacteria can 



be increased and a partial control of the fermentation thus secured. 



Tests for the Quality of Milk. — Methods by which the cheese 



maker can determine, in a rough manner, the kinds of bacteria present 



Fig. I3S- — The type of curd obtained from milk in which the acid-forming flora 

 consists almost whoUy of Bad. lactis acidi. No gas holes and no marked mechanical 

 holes as the curd has "matted" almost perfectly. {Original.) 



have been devised. The bacteria most dreaded and most frequently 

 present are those of the B. coli-aerogenes group. 



The method most frequently used for theijr detection consists in 

 incubating a sample of the milk to be tegted at temperatures ranging 

 from 35° to 40° for a few hoiurs and noting the type of cufd that is 

 formed. Milk suitable for cheese making should show the solid curd 

 characteristic of the Bact. lactis oarfj group, while gassy curds or soft 



