14 BUTTER-MAKING AND COMTOSITION Ol' MILK 



foods as well-cured clover hay and bran seem to injpart desirable 

 flavors to milk and butter. 



The presence of these volatile fats in butter is quite uniform, 

 and is a distinguishing feature of pure butter-fat. The detection 

 of adulteration of butter with foreign fats is based chiefly upon 

 the presence of these volatile fats. The characteristic desirable 

 flavor of butter is also believed to be due to the presence of the 

 volatile fats. The volatile fats vary but slightly during the dif- 

 ferent seasons of the year. They are present in the greatest 

 proportion during the spring and early summer months, when 

 cows are fed on grass, and also during the early stage of the period 

 of lactation. They decrease gradually as the lactation period 

 advances. 



Volatile fats comprise about 8 per cent of the total fats in 

 milk. 



Non-volatile Fats. — This group constitutes about 92 per cent 

 of the total fats in butter. Chemists now agree that palmitin, 

 stearin, olein, and myristin are the most important ones to be 

 considered, as will be seen from the table quoted from Richmond. 



These non-volatile fats are of special importance, as the 

 relative amount of each of these fats largely causes the variation 

 in the hardness and softness of the butter and butter-fat. The 

 melting-point of these difl'erent fats varies according to the dif- 

 ferent investigators : olein is a liquid at ordinary temperatures and 

 melts at about 41° F.; stearin, on the other hand, has a melting- 

 point of about 150° F.; palmitin also has a high melting-point, 

 namely, about 142° F.; myristin melts at about 129° F. 



Olein has been found to be present in the greatest propor- 

 tion during the spring, when cows are fed c)n grass. When 

 cows are fed on normal dry food, as in the winter time, it is present 

 in a much less degree. This, together with the small increase of 

 .volatile fats, is the cause of the softer butter so frequent in the 

 spring. The hardness of the butter in the fall or winter is due 

 chiefly to the presence of a slightly increased amount of the fats, 

 with a high melting-point, as mentioned above. 



From what has been said above, one is led to believe that 

 by melting a sample of butter which contains these different 



