THE CHEMICAL COMPOSITION OF MILK 23 



Butyric 2 C. 



Caproic 1.5 



Caprylic 16.5 



Capric 30.0 



Laurie 1 43.6 



It is from this group of fatty acids that dairy products derive 

 many of their characteristic odors and flavors. Coming from 

 the feed which the cows eat, these volatile substances rapidly 

 pass through the body tissues during the process of digestion 

 and assimilation and find their way into the milk and other 

 secretions. They are rapidly eliminated from the animal 

 body through the excretory organs, and within a short time 

 after digestion is complete, they entirely disappear. Dairymen 

 take advantage of this fact by not allowing the cows to eat 

 aromatic foods such as onions, cabbage, and the like, for several 

 hours before milking time. Butyrin is the principal volatile 

 fat which imparts these odors and flavors to milk and its 

 products. 



THE SERUM OF MILK 



As previously stated, the constituents of milk minus the 

 fat are termed the milk-serum. The serum contains the sub- 

 stances of which nitrogen forms an element, commonly termed 

 the proteids or albuminoids, the sugar or lactose, and the mineral 

 element or ash, and the water. Babcock gives the following 

 composition for milk-serum in percentage of the entire milk : 

 Nitrogen compounds 3.8 per cent ; milk-sugar 4.5 per cent ; 

 citric acid 0.1 per cent ; ash 0.7 per cent ; water 87.3 per cent. 



The proteids or albuminoids 



In this group are all those substances which contain nitrogen. 

 Babcock gives the following substances as constituting the 

 proteids of milk : Casein 3.0 per cent ; albumin 0.6 per cent ; 



1 Van Slyke places this in the insoluble group. 



