ARITHMETIC OF MILK AND MILK PRODUCTS 197 



fat, when we make 135 pounds of butter from 3,000 

 pounds of milk? Applying Rule i, 3 ^ 4 =120, pounds 

 of fat in milk; and 135^-120=1.125 (i l /%) pounds. 

 1.125 I= - I2 5 ( I2 -5 P er cent.) or */. Therefore, the 

 "overrun" is .125 or ^ pound, that is, for each pound 

 of fat in milk there will be made iy$ pounds of butter. 



6. FINDING THE YIELD OF BUTTER 



Rule. To find the yield of butter when the per 

 cent, of fat in milk and the weight of milk are known, 

 find the number of pounds of fat in milk by Rule i 

 and multiply this result by 1.17 or i 1-6. Example: 

 How much butter is made from 1,000 pounds of milk 

 containing 4 per cent, of fat? Applying Rule I, 



= 40, pounds of fat in milk; and 40x1.17= 



46.8, pounds of butter yield. 



In the case of cream apply the foregoing rule, ex- 

 cept to multiply by 1.20 instead of 1.17. 



The application of this rule finds use in checking 

 creamery work. If the yield, in case of milk, is not 

 in proportion to an "overrun" of 15 to 17 per cent, 

 and in case of cream, 20 per cent., one should ascer- 

 tain why and then correct such faults as are found to 

 exist in the form of losses of fat or retaining too little 

 water. When the proportion of butter to fat greatly 

 exceeds 1.17 in the case of milk, too much water is 

 retained in the butter, or else the fat-test is improperly 

 made or the results purposely read too low. 



