BACTERIA IN CHEESE-MAKING. 259 



ripening cheese may be due largely to the chemical ferments, 

 galactase and pepsin, the flavors have certainly a different ori- 

 gin. These enzymes do not produce flavors, and casein which 

 has been rendered soluble by them does not have the charac- 

 teristic cheese taste. There is no doubt that these flavors are 

 due in large part, if not wholly, to the agency of microorgan- 

 isms. We have already noticed how common it is for bacteria 

 to produce decomposition products with high flavors and tastes. 

 It is these decomposition products of the microorganisms grow- 

 ing in the cheese that produce the characteristic cheese flavors. 

 Soft Cheeses. The organisms which produce the cheese 

 flavors are not, however, wholly bacteria. Indeed, it appears 

 that while bacteria have an important share in the ripening, 

 especially in the hard cheeses, other microorganisms play the 

 more important part, at least in producing the ripening of the 

 soft cheeses. Molds are the most important factors in some 

 cases, bacteria in others, and probably yeasts may also con- 

 tribute to the phenomenon. Indeed, the soft cheeses are best 

 divided into three classes according to the relation of micro- 

 organisms to the process, as follows : 



1. Soft cheeses in which bacteria alone are concerned in the 

 ripening, the cheeses ripening from the outside. These include 

 Limburger cheese, Backstein cheese, and some others. 



2. Soft cheeses in which molds contribute to the ripening, 

 the molds growing on the surface and extending to the inte- 

 rior. These include Brie cheese, Camembert cheese, and 

 others. 



3. Cheeses in which molds play an important part in the 

 ripening and grow throughout the entire mass. These include 

 Roquefort, Gorgonzola, and Stilton cheeses. 



The general method of ripening these cheeses is always 

 such as to stimulate and hasten the growth of the needed 

 organisms. The moist curd is frequently wrapped in straw 

 which has, from long use, become thoroughly impregnated 



