116 Milk and Its Products. 



directly in proportion as the diameter is increased and 

 directly with the square of the velocity. The larger 

 the bowl, then, and the greater the speed, the greater 

 the centrifugal force and the more complete the sep- 

 aration. The rate of inflow of milk affects the 

 separation, because the separation is more complete 

 the longer the milk is subjected to the centrifugal 

 force, and the slower the milk flows into a given- 

 sized bowl the longer any particle will be in flowing 

 through it and the more completely will the cream 

 be separated. The temperature of the milk affects 

 the fluidity of the fat globules and their ease of mo- 

 tion upon the other particles of the milk; the warmer 

 the milk the more easily are they separated. A 

 temperature of 76° to 98° F. is the one commonly 

 employed because of the effect upon the texture of 

 the butter. It is desirable that the milk should be 

 separated at as low a temperature as possible without 

 interfering with the completeness of the separation, 

 so that, other things being equal, that separator is the 

 best that separates the milk at the lowest tempera- 

 ture. The physical condition of the milk affects 

 separation by the centrifugal in the same ways that 

 gravity creaming is affected, but to a ver}^ much 

 slighter degree. Small- sized fat globules, viscosity 

 of the milk, and coagulation of part of the casein 

 by incipient fermentations, all tend to make separa- 

 tion more difficult ; but in a majority of cases, un- 

 less the milk is so sour as to be coagulated, it may 

 be completely creamed with a centrifugal separator, 

 but will require a slower feeding (a reduction of 10 



