134 CREAMERY CALCUEATION 



of fat lost in the buttermilk and the skim-milk is quite constant 

 from day to day, and should not exceed .i per cent in the skim- 

 milk and .2 per cent in the buttermilk, according to the Babcock 

 test. Basing the calculations upon the above figures, the theo- 

 retical over''un may be calculated from the composition of the 

 butter as follows: 



If, for instance, we start with looo pounds of milk testing 

 4 per cent fat, there will be a total of 40 pounds of fat. If we skim 

 32 per cent cream irom 4 per cent milk, we should have ijV, or J 

 of it cream, and the remainder skim-milk, or 125 pounds ot 

 cream and 875 pounds of skim-miik. If there were .1 per cent 

 of fat in the skim-milk, there would be a loss of .875 pound of 

 fat during skimming. There woukl then be 39.125 pounds of fat 

 in the 125 pounds of cream (40— .875 = 39.125). If 10 per cent of 

 starter were added to the cream we should get 137.5 pounds of 

 cream testing 28.4 per cent. (125 pounds cream X 1.10 = 137.5 

 pounds cream; 39.125-^137.5X100 = 28.4 per cent fat.) Bv 

 churning this cream we should obtain about 100 pounds of butter- 

 milk. If it tested .2 per cent fat there would be a loss of about .2 

 pound of fat, making a total loss of fat in skim-milk and butter- 

 milk of 1.075 pounds. Subtracting this total loss of 1.075 from 40 

 pounds we would have 38.925 pounds of fat left to be made into 

 butter (40—1.075=38.925 pounds of fat). If the butter on 

 analysis proves to contain 82 per cent fat, the total number of 

 pounds manufactured will be 38.925 ^ .82 = 47.47 pounds of butter. 

 47.47—40 = 7.47 pounds theoretical overrrun, and 7.47-^40X100 

 = 18.7 per cent overrun (theoretical). 



It is evident that the losses of fat will vary according to the 

 different conditions. The richer the cream, and the less fat in 

 the whole milk to be skimmed, the more skim-milk there will be; 

 the thinner the cream and the more fat there is in the milk to be 

 skimmed, the less skim-milk there will be, and consequenth' 

 with the same skimming efiiciency less fat will be lost in the skim- 

 milk. The thinner the cream is the more buttermilk there will 

 be. These conditions must be left for the operator to govern 

 according to the conditions present. 



The actual amount and per cent of overrun as determined 



