CHAPTER XXII. 

 CREAM AND CREAM RIPENING. 



Cream. When milk is placed in a shallow vessel 

 and allowed to stand for a time, the globules of fat, 

 which have a smaller specific gravity than the serum in 

 which they are distributed, rise to the surface of the 

 liquid and form a layer of variable thickness. This 

 layer of fat globules, with a certain amount of milk 

 serum, is known as cream ; it can be poured off or 

 removed in other ways, leaving behind skim-milk, a 

 product comparatively poor in fat. 



In addition to this method of obtaining cream, which may 

 take several hours to complete, cream may be taken from 

 fresh milk by the centrifugal separator in a few minutes. 



The composition of cream is very variable : thick or 

 thin cream can be obtained at will by means of the 

 separator, and the amount of serum left in it even when 

 raised by gravitation processes can be regulated to some 

 extent by " raising " the cream in shallow or deep 

 vessels and varying the temperature at which the milk 

 is kept. The comparative composition of cream, " sepa- 

 rated," and fresh milk is shown below : 



Per cent. 

 Water. Fat. Proteins. Milk-Sugar. Ash. 



Thin cream . .64 28 3.25 4.5 .65 



Thick . 44 45 3.05 2.7 .60 



Separated milk .90 .1 3.9 4.9 .76 



Skim-milk (shallow pans)... 1-1.5 



Fresh milk , . 87 3.9 3.4 4.75 .75 



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