RELATION OF MICROORGANISMS TO CHEESE. 



349 



TESTS FOR THE QUALITY OF 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. coli-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 



