172 Dairy Bacteriology. 



This digesting ferment found in milk is known as galac- 

 iase. Compounds are formed in milk thus preserved 

 that are similar to those found in a ripe cheddar cheese. 

 Many experiments have been made with pasteurized 

 milk, but it has not been possible to produce typical, nor- 

 mal cheese from thoroughly pasteurized milk. Such 

 cheese are markedly deficient in the typical flavor of 

 cheddar cheese. From this fact it is believed that the 

 inherent enzymes of milk are a factor of some import- 

 ance in the ripening of this type of cheese, at least, if not 

 of all types. 



In the past, other factors have been thought to be of 

 importance. Duclaux, a French bacteriologist, consid- 

 ered that the enzymes formed by the digesting bacteria 

 -are responsible for the ripening. It is now known that 

 they can have but little if any part in the process, since 

 they are not present in all cheese in sufficient numbers 

 to have any marked effect, and since the acidity of the 

 cheese mass will not permit of their development. 



Other types of bacteria have been considered by bac- 

 teriologists to be of importance in the ripening process, 

 but it is certain that the purely digestive change in the 

 mass of the cheese can be accounted for through the 

 action of the factors already noted. 



Flavor production. The flavor of any type of cheese 

 is the most important characteristic, just as it is in but- 

 ter, for it is largely the flavor that determines the selling 

 value of the product, and is the most difficult thing to 

 control. It has been thought that the flavor-producing 

 substances were derived from the paracasein of the curd 

 and were produced by the factors that are concerned in 

 the digestion of the paracasein. It has been shown that 

 a cheese may be thoroughly ripened as far as its physical 

 properties are concerned; that it may contain the end 



