RELATION OF MICROORGANISMS TO CHEESE. 349 



TESTS FOR THE QUALITY or MILK. Methods by which the cheese 

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

 have been devised. The bacteria most dreaded and most frequently 

 present are those of the B. coll- aero genes group. 



The method most frequently used for their detection consists in 

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



FIG 82 The type of curd obtained from milk in which the acid-forming flora 

 consists almost wholly of Bact. lactis acidi. No gas holes and no marked mechan- 

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



from 35 to 40 for a few hours and noting the type of curd that is formed. 

 Milk suitable for cheese making should show the solid curd character- 

 istic of the Bact. lactis acidi group, while gassy curds or soft and partially 

 digested curds are indicative of bacteria that are likely to be harmful 

 in the cheese. '!'.'!' ^ 



An improvement over the fermentation test of foreign origin has 



