RELATION OF MICROORGANISMS TO CHEESE. 361 



mate the Cheddar flavor. The formation of the eyes is inhibited by salt, 

 as is indicated by their relative scarcity in the outer layers of the cheese. 

 Jensen has shown that the eyes are due to the fermentation of lactates 

 with the formation of propionic and acetic acids, and carbon dioxide. 

 The causal organism is found in the milk and the whey rennet. It is 

 believed that lactic bacteria of the Bad. bulgaricum group are important 

 factors in the ripening of Swiss cheese. They are present in large numbers 

 in the rennet and cheese. Mixed cultures of an organism of this group 

 and a mycoderma are used with success for the inoculation of the whey in 

 which the rennet is to be soaked. The exact role of this form of lactic 

 organism is not known; de Freudenreich considered them to be concerned 

 in the proteolysis of the paracasein, since he had found that the content 

 of sterile milk in soluble nitrogen increased when inoculated with the 

 organism. It is probable that the formation of eyes and the flavoring 

 compounds are due, in part at least, to the same factors. 



In the other kinds of cheeses to be described, the role of the acid-forming 

 bacteria is similar, if not identical, to their role in Cheddar cheese, i.e., 

 in activating the pepsin of the rennet and in preventing the growth of 

 putrefactive bacteria. The factors concerned in flavor development are 

 different. 



ROQUEFORT CHEESE. This cheese, which is prepared almost ex- 

 clusively in the Department of Aveyron in southern France, is made 

 from sheep's milk. Its most striking characteristic is the marbled or 

 mottled appearance of the interior, due to the growth of a mold, Penicillium 

 roqueforti, Thorn. The curd is inoculated with the mold, when it is 

 placed in the press, by sprinkling the curd with bread crumbs on which 

 the mold has grown. The growth and sporulation of the mold in the 

 interior of the cheese are favored by piercing it with small needles, thus 

 admitting air. The characteristic flavor is due, partially at least, to the 

 mold. 



This cheese is cured in caves having a temperature below 15. The 

 fermentative processes are apparently closely dependent on the moisture 

 and temperature conditions of the curing room. This emphasizes the 

 importance of biological factors in the ripening process. 



GORGONZOLA CHEESE, prepared in Italy from cow's milk, and STILTON 

 CHEESE, made in England are similar to Roquefort in appearance and are 

 supposed to contain the same mold or a closely related type often called 

 Penicillium glaucum. 



