NORMAL MILK AND ITS PRODUCTS AS FOOD 15 



The method of separation affects the age of the skim milk 

 and the per cent fat remaining in the skim milk. 



The shallow pan gravity system of creaming leaves 

 from 0.3 per cent to 0.5 per cent fat in the skim milk. This 

 method requires about thirty-six hours for the cream to 

 rise. During this time the temperature of the milk is 

 about 60° F., and in some instances higher. These con- 

 ditions, although favorable for a high per cent of fat, are 

 not conducive to the best quality of skim milk, as the 

 various ferments are more or less active at the above- 

 mentioned temperature. 



The " Cooley " or deep setting system of creaming pro- 

 duces skim milk which contains about 0.2 per cent to 0.4 

 per cent fat. The cream rises in about twenty-four hours, 

 and during this time it is kept at from 40° to 50° F. This 

 temperature is so low that the ferments have little or no 

 deleterious effect on the quality of the skim milk. 



The skim milk obtained by the water-dilution method 

 of separation will not be considered in this connec- 

 tion. 



Most of the dairy farmers in the central west now have 

 hand separators, which do more efficient skimming than 

 can be accomplished by any of the gravity systems. The 

 skim milk obtained by the centrifugal method, under ideal 

 conditions, does not contain more than o.i per cent butter 

 fat. The machines, however, are seldom operated under 

 ideal conditions, and the milk is not always skimmed under 

 conditions most conducive to the complete removal of the 

 fat. Tests and observations by the authors warrant the 

 statement that skim milk from hand separators on the farm, 

 on an average, contains about 0.2 per cent fat. This 

 skim milk is fresh, and many of the impurities and germs 

 have been removed in the process of separation. Fresh 



