CHAPTER VIII. 



BACTERIA AND CHEESE MAKING. 



Butter, such as that of the sweet-cream type that is 

 highly esteemed in many parts of the world, may be 

 made without the aid of bacteria, but no important kind 

 of cheese can be made under commercial conditions with- 

 out them. 



Types of cheese. Cheese consists of the fat and the 

 precipitated casein of milk, together with a large amount 

 of water and the salts found in milk. The numerous 

 types of cheese may be divided into two groups, depend- 

 ing on the manner in which the curdling of the milk is 

 brought about. Sour-milk cheese is made from curd, 

 formed as a result of the acid fermentation of the milk. 

 Thus, at the very first stage in the making of this type, 

 the importance of bacteria is apparent. 



The second type is that made from curd, which is pre- 

 cipitated by the addition of rennet to the milk. This 

 type may also be divided into two groups, depending 

 upon their texture ; the hard cheese, and the soft cheese. 

 The ordinary cheddar, the common American type, is 

 the most important example of the hard cheese; Lim- 

 burger, of the soft cheese. Cheese are designated as 

 hard or soft, depending upon the amount of whey that 

 is retained in them during the making process. The 

 moisture content has an important influence on the type 

 and amount of life that develops on and in the curd 

 mass, and as will be seen, the ripening and flavor of the 

 cheese are dependent upon these biological factors. 



The two groups of hard and soft cheese have no 

 sharply defined limits, but merge into each other. The 

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