CHAPTER VI. 



CREAMING. 



Definition. Milk upon standing soon separates into 

 two portions, one called cream, the other skim-milk. This 

 process of separation is known as creaming, and is due 

 to the difference in the specific gravity of the fat and 

 the milk serum. The fat being light and insoluble, rises, 

 carrying with it the other constituents in about the same 

 proportion in which they are found in milk. The fat 

 together with these other constituents forms the cream. 

 After the cream has been skimmed off, there remains a 

 more or less fat- free watery portion called skim-milk. 



Processes of Creaming. The processes by which milk 

 is creamed may be divided into two general classes : ( i ) 

 that in which milk is placed in shallow pans or long 

 narrow cans and allowed to set for about twenty-four 

 hours, a process known as natural or gravity creaming; 

 (2) that in which gravity is aided by subjecting the milk 

 to centrifugal force, a process known as centrifugal 

 creaming. The centrifugal force has the effect of increas- 

 ing the force of gravity many thousands of times, thus 

 causing an almost instantaneous creaming. This force 

 is generated in the cream separator. 



Before the days of the centrifugal cream separator, 

 creameries either bought the milk and creamed it at the 

 creamery by the gravity process, or bought and gathered 

 the cream that had been creamed at the farms by the same 

 process. The practice of gathering cream is now exten- 

 sively employed by creameries throughout the country; 



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