RELATION OF BACTERIA TO DAIRY PRODUCTS 571 



KELATION OF BACTERIA TO CHEESE 



The action of bacteria in the processes of cheese-making and 

 ripening is much more complex than in the case of butter. 

 The quality of the cheese is dependent on the sanitary quality 

 and bacterial flora of the milk from which it is made, and, as 

 in the ripening of cream for butter, so in the ripening of milk 

 for cheese, the prime essential is to favor the development of 

 the lactic acid bacteria while holding other kinds in check. If 

 the milk is clean and undergoes the proper lactic fermentation 

 during the ripening process, there should be little difficulty 

 in developing the desired flavor and texture during the curing 

 process, but if the original milk contains gas-producing bacteria, 

 yeasts or oidium lactis, it will be difficult to develop a cheese of 

 high quality. 



Many theories regarding the changes which take place during 

 cheese ripening have been advanced, and much research work 

 has been done in recent years both from the chemical and 

 biological standpoint. While large numbers of the bacteria in 

 the milk pass out in the whey, large numbers are also left in 

 the curd and, these being held at warm temperatures during 

 the cheddaring process, develop with enormous rapidity. It 

 has been found that fresh cheese may contain more than 

 1,000,000,000 bacteria to a gram, and it has been shown that 

 these play an important part in the later ripening of the cheese. 

 It has also been shown that the enzymes normal to milk and 

 in the rennet extract are factors in the ripening process. 



In the ripening of the different groups of fancy cheeses, 

 special organisms are responsible for the flavor and texture of 

 the ripened cheese. In such cheeses as the Roquefort, Gorgon- 

 zola, and Stilton, in addition to the action of the lactic acid 

 organisms, the special flavor is developed by the growth of 

 certain kinds of molds through the cheese. In the case of Lim- 

 burger, the ripening of the cheese is caused by the enzymes 



