MILK AND ITS PRODUCTS 



169 



purpose as food as ordinary water. It should not be 

 con rhided from the high water content that milk has a 

 low food value. 



155. Fat. The fat is commercially the most valuable 

 pan of milk. It is also the most variable in amount. It 

 ma> range from 2.5 to 7.5 per cent and occasionally even 

 beyond these limits. The fat exists in the form of minute 



FIG. 47. Photomicrograph showing fat globules 

 in Shorthorn milk. Magnified 400 diameters. 



globules, too small to be seen by the naked eye but readily 

 seen under a microscope. It is in a state of suspension, that 

 is, the fat globules are floating in the milk. When milk 

 stands undisturbed for some time, the fat rises to the top in 

 the form of cream. Churning of cream is the uniting of 

 these, fat globules by mechanical means until they form a 

 lump of butter. The main factors influencing the amount 

 of fat are : (1) breed, (2) stage of lactation, (3) individuality 



