46 CLEAN MILK 



ferences, in the size of the globules, there are great individual differ- 

 ences in the same breed. The fat globules are arranged in groups 

 or clumps in milk instead of being uniformly scattered throughout 

 the fluid. This is of considerable practical importance, for milk 

 which has been separated or heated (pasteurized) does not cream 

 so well because the clumps of fat globules are broken up and so do 

 not rise so quickly or completely. For example, milk is passed 

 through a separator revolving at the rate of 1,200 revolutions a 

 minute, not fast enough to separate the milk from the cream (which 

 is sometimes done to remove the dirt from milk or to " clarify " it), 

 and the milk is bottled. The cream will rise from this milk slowly 

 and incompletely, and the cream, when it has risen, will appear so 

 thin that a twenty per cent, cream may not seem thicker nor richer 

 than rich milk. 



Pasteurizing milk will cause much the same result, if the milk 

 is subjected to considerable agitation in the process. 



If milk is cooled within a few moments of pasteurization to 

 40 F. and bottled immediately the cream will rise quickly into a 

 smaller and denser mass than on unheated milk, but showing a good 

 cream line. 



The mineral matter in milk comprises a very small amount 

 of variety of salts and altogether they do not form quite one per 

 cent, of the whole milk. 



The following table perhaps fairly represents the composition 

 of what might be called average milk * from a large herd of average 

 cows of various breeds : 



Per Cent. 



Water 87.00 



Fat 4 00 



Proteids 3.30 



Sugar 495 



Mineral Matter 0.75 



* The U. S. Pure Food Act of 1906 fixes the standard for milk as fol- 

 lows: Solids not fat, 8.5 per cent.; milk fat, 3.25 per cent.; milk solids, total, 

 11.75 per cent. Skimmed milk to contain 9.25 per cent, of total solids. 



