Agricultural Chemistry. 



series. The average percentage composition of milk fat is about 

 as follows: 



Per cent 



Butyrin 3.85 



Caproin 3.60 



Caprylin 0.55 



Caprin 1.90 



Laurin . . 7.40 



Per cent 



Myristin 20.20 



Palmitin 25.70 



Stearin 1.80 



Olein.. 35.0 



The properties of these fats are variable, but the important 

 fact to notice is the occurrence in milk fat of the first three or 

 four fats in the above list, but mere traces of which are present 

 in other animal fats. Olein and the first four members of the 

 above list are liquid fats ; the others are solid, stearin being the 

 hardest. About 8.0 per cent of the fatty acids, chiefly consisting 

 of the first three in the series, are soluble in water. The soluble 

 acids have a low boiling point and can be separated from the other 

 fatty acids by distillation. These facts serve to distinguish butter 

 fat from animal fats such as tallow, which contains but traces of 

 soluble and volatile fatty acids. Milk fat, however, varies con- 

 siderably both in composition and physical properties, being 

 affected somewhat by feed, period of lactation and other circum- 

 stances under which the cows are kept. 



Fat exists in milk in the form of minute globules, varying in 

 diameter from .0016 to .010 m. m. In the milk of Jersey and 

 Guernsey cows the average size of the globules is considerably 

 larger than in Holstein milk ; also in the milk of recently calved 

 cows the globules are larger than in that of cows far advanced in 

 lactation. This fact has an important practical bearing upon 

 the speed with which cream rises. The milk of the Jerseys and 

 Guernseys throws up its cream very rapidly, while from the milk 

 of the Holstein and Ayrshire breeds the cream rises relatively 

 slower. 



The proteins. The two most important proteins of milk are 

 casein and albumin. Traces of others are present, but they are 



