CHAPTER II.* 



THE RELATION OF MICROORGANISMS TO BUTTER. 



Butter is the fat of milk that has been largely freed from the other 

 constituents of milk by the processes of creaming and churning. If 

 milk is allowed to stand, the fat, which is in the form of minute globules, 

 accumulates in the upper layers of the milk because its specific gravity 

 is much lower than that of milk serum. In modern practice the fat is 

 concentrated in a portion of the milk by passing the milk through a cream 

 separator. In the rapidly revolving bowl of the separator the centrif- 

 ugal force exerted is many times greater than that of gravity and the fat 

 is rapidly and efficiently removed. The cream, which is obtained by 

 these methods, contains varying amounts of fat which is further concen- 

 trated, by subjecting it to agitation in the churning process. The globules 

 of fat cohere to form larger and larger masses until the entire amount of 

 fat is brought into a single mass, the butter. 



TYPES OF BUTTER. 



SWEET-CREAM BUTTER. If little or no increase in the acidity of the 

 milk or cream develops, previous to churning, the butter will have certain 

 marked characteristics and is called sweet-cream butter. It is especially 

 characterized by its low flavor, since it has only the flavor of the fat of 

 milk which is not marked. This is usually known as the primary flavor 

 of butter. Sweet-cream butter is also marked by the rapidity with which 

 it undergoes decomposition changes, especially when it is made from 

 raw cream. 



SOUR-CREAM BUTTER. If the cream is allowed to undergo the acid 

 fermentation, the butter will differ markedly both in degree and kind of 

 flavor from that prepared from sweet cream, and as a rule its keeping 

 qualities are much better than those of sweet-cream butter. This type 

 of butter is made throughout northern Europe, England and her colonies, 



* Prepared by E. G. Hastings. 



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