CREAMING 25 



tage that the feeding value of the skim milk has 

 been materially lessened, the holding capacity and 

 the material to be handled is twice as much. Re- 

 peated experiments show that the loss in skim milk 

 may be from 0.7 to 1.5 per cent, of fat. 



Mechanical separation. In mechanical separa- 

 tion of cream sufficient centrifugal force is devel- 

 oped to cause a practically instantaneous separation 

 of the cream from the skim milk as the milk flows 

 through the rapidly revolving bowl, any one particle 

 of milk being subjected to the centrifugal force only 

 a few seconds. 



Centrifugal force. Centrifugal force is that force 

 which causes a body to fly away from the center 

 around which it is revolving. In the shallow-pan 

 and deep-setting systems, the force of gravity act- 

 ing upon the heavier skim milk draws it to the bot- 

 tom and forces the cream to the surface, requiring 

 hours for complete separation. In the mechanical 

 separator sufficient centrifugal force is developed to 

 cause the skim milk and cream to form two distinct 

 vertical layers in the rapidly revolving bowl during 

 the short time they are in it, the skim milk layer be- 

 ing next the wall of the bowl. 



Centrifugal separator. When a hollow vessel or 

 bowl partly filled with a liquid is revolving rapidly 

 enough, the contents are distributed around the 

 sides, forming a vertical wall, with the center empty 

 from top to bottom. If the liquid consists of two 

 materials differing in their specific gravity, as fat 

 and skim milk, the heavier will be drawn toward 

 the outside, forcing the lighter to the center and 



