198 MODERN METHODS OF TESTING MILK 



milk containing 4.5 per cent, of fat. If, in place of 

 cream, a milk containing more than 3.5 per cent, of 

 fat were used, the process would be the same. 



(a) If it is desired to know how much such cream 

 must be used in standardizing 1,000 pounds of such 

 milk, divide 1,000 by 20.5 (C — B) and multiply by 

 I (B — A,) which will give 48.8 pounds of cream to be 

 added and 1048.8 pounds of the modified milk. 



(b) If it is desired to know how much such cream 

 and milk to use to make 1,000 pounds of the modified 

 milk, divide 1,000 by 21.5 (C — B) + (B — A), which 

 is 46.5, and multiply this amount by 20.5 (C — B) and 

 by I (B — A), which will give 953.5 pounds of 3.5 

 per cent, milk and 46.5 pounds of 25 per cent, cream. 



(2) When the per cent, of fat in milk is to be in- 

 creased by removing a portion of the milk-serum 

 (skim-milk). Rule. — From the per cent, of fat de- 

 sired in the modified milk subtract the per cent, of fat 

 in the milk to be modified, and the result is the number 

 of pounds of skim-milk to be removed. The per cent, 

 of fat in the modified milk is the number of pounds to 

 use of the milk to be modified. This is done by sep- 

 arating the cream from a portion of the milk and then 

 adding it to the normal milk. The skim-milk can be 

 assumed to contain practically no fat. Example : How 

 much skim-milk should be removed from milk con- 

 taining 3.9 per cent, of fat, in order to produce a mod- 

 ified milk containing 5 per cent, of fat? 



A=3.9 ^^^^^ B— C=5 (pounds of milk to use). 



C=o.o 



B=5 



B— A=i I (pounds of skim-milk to remove). 



Skim-milk 



