334 CREAM SEPARATION 



strong enough to produce a rich cream. Letting down the speed 

 of the handle from 60 to 45 revolutions per minute, cuts the force 

 down nearly a half. 



2. The amount of dirt in the bowl. — As the slime accumu- 

 lates in the bowl, the cream becomes thinner but there will be 

 more of it. There may not be an increased fat loss until long 

 after the cream has begun to run thin. 



3. Rate of inflow of milk. — The faster the milk goes in, the 

 thinner the cream will be. If the milk hopper is kept full all the 

 time, the cream will test less than it will if the machine is 

 allowed to run empty occasionally. 



4. Per cent of fat in the milk. — A rich milk yields a richer 

 cream than a thin milk, even when the separator is run exactly 

 the same in the two cases. Rich cream for whipping can easily 

 be produced by turning some of the cream just separated back 

 into the milk to come through a second time. 



5. Temperature of the milk when separated. — Cold cream 

 is thicker and more sticky than warm cream and when flowing 

 out of the bowl drags along the sides of the cream screw and 

 effects a change in relative points of outflow of skim milk and 

 cream, thereby causing a richer cream to be delivered when the 

 milk is cold than when it is warm. To do best work, most 

 machines require a milk temperature of 75 degrees or above. 



6. Cream will rise on cream. — Cream that has stood a few 

 hours will be much richer at the top than towards the bottom. 

 If the top be poured off to make butter at home, the portion 

 sold will be thinner than the average. 



Efficiency in Skimming. — The quantity of fat lost in the 

 skim milk from centrifugal cream separators is largely a con- 

 trollable matter. The chief factors are as follows : 



1. Speed of the Machine. — The thoroughness of skimming 

 or completeness of the removal of the fat is a result of force act- 

 ing through time. If more force is applied a shorter time will 

 be required, or in other words, the milk need not remain in the 

 machine so long to have the same work done upon it It there- 

 fore may be put through more rapidly. If the flow through the 

 machine is held constant, however, the effect is toward a more 



