336 



SKIMMED MILK BUTTER 



and he gives, as a formula connecting the specific gravity and per- 

 centage of fat in cream, the following : 



F 



32-0 - 0-892 , 



where F = per cent of fat, G = lactometer reading (i.e., specific 

 gravity x 1000 - 1000) and D = true specific gravity. 



This formula does not apply to clotted cream. 



Skimmed Milk is similar in composition to ordinary milk, with 

 the exception that it contains little or no fat. The other constituents 

 water, sugar, casein, etc. though preserving the same ratio to each 

 other, are slightly raised in percentages. Skimmed milk from shallow 

 setting usually contains anything between 0-4 and 2 per cent of fat, 

 while with a good separator, the amount is usually from 0*05 to 0'3 

 per cent. Its specific gravity is usually between 1-034 and 1-037. 

 Its average composition, as given by Fleischmann, is 



Butter is produced by agitating or "churning" milk, or, more 

 generally, cream, until the fat globules coalesce. The resulting semi- 

 solid mass which separates from the butter-milk, consists largely of 

 completely continuous fat, a few of the original globules, however, re- 

 maining. Under the microscope, many spherical globules are visible, 

 which, according to recent observations, consist of minute drops of 

 enclosed butter-milk or water and not of fat. 



The effect of churning is purely mechanical ; the fat globules are, 

 by violent motion, knocked together and adhere, thus giving rise to 

 larger, irregular masses, which, in turn, collide together or with other 

 fat globules. In this way the masses of fat gradually increase in size, 

 portions of the aqueous liquid becoming enclosed during their forma- 



l ln the author's experience, separated milk generally contains much less fat 

 than this. With good management, probably not more than 0-1 per cent of fat should 

 be left in the separated milk. 



