102 MANAGEMENT OF DAIRY PLANTS 



The value of s is then determined as follows: 



m X p = (m — s) pi + s X a or 

 ^ m (pi — p) 

 Pi— a 



Or pounds skim milk obtained = pounds whole milk X 

 per cent fat in cream — per cent fat in whole milk 

 per cent fat in cream — per cent fat in skim milk 



This formula becomes practical, inasmuch as the weight of 

 the whole milk skimmed is always known, and the test of the 

 cream and skim milk obtained as well as the test of the whole 

 milk are known figures. 



As the weight of the cream in a whole milk plant is usually 

 determined with difficulty, the above formula may also be of 

 value in determining the amount of cream obtained from the 

 milk as c = m — s. Or without figuring the amount of skim 

 milk, the amount of cream may be determined from the fol- 

 lowing formula; 



m (p— a) 



c = 



Pi- 



Or pounds cream obtained = pounds whole milk X 

 per cent fat in whole milk — per cent fat in skim milk 

 per cent fat in cream — per cent fat in skim milk 



Example I. — Determine the amount of fat contained in the 

 skim milk obtained from skimming 30,000 pounds of milk 

 testing 3.6 per cent of fat when the cream obtained tests 33.6 

 per cent of fat and the skim milk .1 per cent of fat. 



Answer: 



30,000(^^.6 — ^.6) , „, , 

 g ^ o_j v^o o_/ ^ 26,865.67 pounds. 



26,865.67 X .001 «= 26.87 pounds of butter fat. 



Example II. — Determine the overrun obtained in a cream- 

 ery for a day when they received 20,000 pounds of 4 per cent 



