32 DAIRYING 



and adding to it the increase that will come from the water, 

 salt and curd when the butter is made. This increase is called 

 the overrun and it is usually expressed as a per cent, of the fat 

 in the milk or cream skimmed and churned. If 1000 Ibs. of 'milk 

 testing 3.5 per cent, fat is made into butter there will be a slight 

 loss of fat in the skim milk and in the buttermilk. Nearly all the 

 remainder of the fat of the milk should be recovered in the butter 

 and when the water, salt and curd are added to this butter fat, 

 the net increase in weight will be about 16 per cent, of the fat in 

 the milk. In this case 1000 Ibs. milk multiplied by its test, 3.5 

 per cent, fat gives 35 Ibs. butter fat and the approximate amount 

 of butter that may be made from it is found by adding 16 per cent. 

 lo the pounds of butter fat or 35 pounds x 1.1 6- 40.6 pounds butter- 

 This weight of butter may be reduced by greater losses in the skim 

 milk and butter milk than are included in this calculation, also by 

 incorporating less water in the butter and from excessive losses 

 by waste of milk, cream and butter that sticks to the cans, vats, 

 churn, etc., during the skimming and churning of the milk and 

 cream. 



441. The overrun or yield of butter from milk and cream 

 is influenced by: (1) The losses in skimming; (2) the losses in 

 churning; (3) the losses from waste; (4) the accuracy of weigh- 

 ing, sampling and testing the milk, cream and butter; (5) the 

 amount of water, salt and curd incorporated in the butter. 



When a practice is adopted that gives a uniform skimming and 

 churning and accurate weights and tests are made of the milk, 

 cream and butter, the yield of butter or the overrun will be uniform 

 from day to day. 



CALCULATING THE OVERRUN. 



442. The overrun is calculated by first multiplying the weight 

 of milk or cream by its test. This gives the pounds of butter fat 

 handled ; second, weigh the butter and from it subtract the pounds 

 of butter fat found by the first calculation; third, find what per 

 cent, the difference between the weight of butter and of butter 



