Bacteria in the Cheese Industry. 155- 



addition to peptones, numerous other intermediate prod- 

 ucts are formed ranging from albumens to ammonia. 

 Amido acids (leucin and tyrosin) are present in an old 

 cheese. The chemical reaction of cheese is generally 

 slightly acid to phenolphthalein, although in an old cheese 

 where putrefactive changes are going on, the reaction 

 may be alkaline. 



The changes that occur in a ripening cheese are for the 

 most part confined to the proteids. The fat remains 

 practically unchanged. In the green cheese considerable 

 milk-sugar is present, but as a result of the fermentation 

 that occurs, this is rapidly converted into acid products. 



163. Bacterial flora of cheese. It might naturally 

 be expected that the green cheese, fresh from the press 

 would contain practically the same kind of bacteria that 

 are in the milk, but a study of cheese shows a peculiar 

 change in the character of the flora. In the first place, 

 fresh cottage cheese made by the coagulation of the 

 casein through the action of acid, has a more diversified 

 flora than cheese made with rennet, for the reason, as 

 given by Lafar, 1 that the fermentative process is farther 

 advanced. 



When different varieties of cheese are made from milk 

 in the same locality, the germ content of even the ripened 

 product has a marked similarity, as is illustrated by 

 Adametz's work 2 on Emmenthaler or Swiss hard cheese, 

 and Schweitzer Hauskase, a soft variety. Of the nine 

 species of bacilli and cocci found in mature Emmenthaler, 

 eight of them were also present in ripened Hauskase. 



Different investigators have studied the bacterial flora 

 of various kinds of cheese, but as yet no systematic 

 comparative work has been done in an extended manner. 



1 Lafar, Technical Mycology, p. 216. 

 8 Adametz, Landw. Jahr., 18: 228. 



