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 spe- 

 cific gravity is much lower than that of milk serum. In modern prac- 

 tice 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 separa- 

 tor the centrifugal force exerted is many times greater than that of grav- 

 ity and the fat is rapidly and efficiently removed. The cream, which is 

 obtained by these methods, contains varying amounts of fat which 

 is further concentrated, by subjecting it to agitation in the churning 

 process. The globules of fat cohere to form larger and largermasses 

 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 

 quaUties are much better than those of sweet-cream butter. This ty^t 

 of butter is made throughout northern Europe, England and her 



* Prepared by E. G. fastings. 



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