12 BUTTER-MAKING. 
The presence of these volatile fats in butter is quite uniform, 
and is a distinguishing feature of pure butter-fat. The detec- 
tion 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 pres- 
ence of the volatile fats. The volatile fats vary but slightly 
during the different 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. 
About 8% of the total fats in milk is volatile fats. 
Non-volatile Fats.——This group constitutes about 92% 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 Rich- 
mond. 
These non-volatile fats are of special importance, as the 
relative amount of each of these fats largely causes the varia- 
tion in the hardness and softness of the butter and butter-fat. 
The melting-point of these different fats varies according to 
the different investigators: olein is a liquid at ordinary tem- 
perature 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 pro- 
portion during the spring, when cows are fed on 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, 
