SEPARATION OF CREAM. 329 



added to the milk, produce putrefactive and undesirable results. 

 Much well-water also is tainted to a greater or lesser degree. 

 Especially is this so with water from shallow wells. Butter 

 made from cream which has been diluted with water usually 

 has a flatfish poor flavor. 



The efficiency of separation of diluted and undiluted milk 

 is reported by Wing * to be as follows : 



Diluted with 25% warm water set at 60° F. (39 trials), 0.77% 

 fat in skim-milk; 



Undiluted, set at 60° F (30 trials), 1.00% fat in skim-milk 



Undiluted, set at 40° F (26 trials), 0.29% " " " 



Centrifugal Creaming. 



In the separation of cream by centrifugal machines, the 

 same principle is used as in the gravity system of separation. 

 The only difference is that in the centrifugal method the force 

 which separates the cream from the milk is generated by 

 artificial methods, and acts in a horizontal direction; in the 

 gravity system the force which separates the cream from the 

 milk is only that which results from the difference in the specific 

 gravity of the cream and the skimmed milk, and the force 

 acts in a vertical direction. The force generated in the sepa- 

 rator is several hundred times greater than the natural force 

 in the gravity method. For this reason the cream separates 

 almost instantaneously after the milk has entered the separator 

 and is exposed to the centrifugal force. 



Advantages. — The centrifugal separator has several advan- 

 tages over the gravity method, which are apparent without 

 detailed elaboration. In the first place, the range of tem- 

 perature and condition of the milk at which the cream can be 

 successfully separated is much greater than that for successful 

 separation by the gravity method. Second, a much better 

 quality of cream can be obtained by the centrifugal system, 



* Milk and Its Products, p. 105. 



