36 



PROPERTIES OF MILK 



difference in weight, or specific gravity, of the fat-globules and 

 the serum. The force which acts upon the globule of fat is the 

 difference in weight between the fat-globule and the serum which 

 it displaces, minus the resistance with which it meets in its upward 

 passage. This force is great in milk with a high degree of vis- 

 cosity and slighter in milk of a limp and liquid consistency. 

 While the addition of water to milk reduces its viscosity it also 

 lowers its specific gravity. Hence, the so-called " dilution cream 



FlG 5 _ Standardized milk. Showing the amount of cream on milk containing 

 the designated per cent of butter-fat. (From Bui. 92, 111.) 



separator " has, generally speaking, little to recommend it. 

 While the skim-milk may give a lower test we must remember 

 that there is a greater quantity of it. Furthermore, it lacks the 

 palatability and feeding value of undiluted skim-milk. But this 

 is a point that need not be labored, since the hand separator has 

 all but superseded the different methods of setting milk. 



In normal milk, the amount of fat left in the skimmed milk by 

 natural creaming is about .4 per cent. The fat which is left in 

 this skimmed milk is largely composed of very small globules. 

 This is due to the fact that the resistant force on these small 

 globules is equal to or greater than the buoyant force acting upon 

 them. 



