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, 



