THEORETICAL OVERRUN 129 



2. To calculate the amount of buttermilk per loo 

 pounds of milk. 



Rule: This is approximately found by increasing the 

 pounds of butter fat in the cream by one-sixth and sub- 

 tracting the result from the total pounds of cream. 



Example : How much buttermilk from lOO pounds of 

 4% milk yielding lo pounds of cream testing 40% ? 



10 X .40 = 4.0 = lbs. of butter fat. 

 4X11/6 = 4.66, 10 — 4.66 = 5.34= No. lbs. 

 buttermilk. 



Overrun. The method of calculating the actual over- 

 run at creameries has already been discussed in Chapter 

 XI. With the following known conditions the theoretical 

 overrun can be calculated with a fair degree of accuracy : 



(i) Average per cent of fat in butter. 



(2) Loss of fat in skim-milk. 



(3) Loss of fat in buttermilk. 



Problem : 100 pounds of milk testing 4% yields cream 

 testing 40%. Test of skim-milk is .05%, that of butter- 

 milk .15%. Per cent of fat in butter is 84. Calculate 

 butter and overrun. 



By applying the rules for calculating skim-milk and 

 buttermilk we find that there will be 90 pounds of skim- 

 milk and 5.34 pounds buttermilk. 



.90 X .05 = .045 = lb. fat in skim-milk. 

 •0534 X .15 = .008= lb. fat in buttermilk. 



Total loss = .053 



4 — .053 = 3,947 = fat made into butter. 

 3.947 -^ .84 = 4.70 = lbs. butter made. 

 4.70 — 4= .70 = overrun in lbs. 

 .7-^4X100=17.5 = overrun in per cent. 



