20 Milk and Its Products. 



determination of the specific gravity became of little 

 value. Unscrupulous dairymen soon learned that 

 water could be added to milk and fat or cream 

 taken from it in such proportions that the specific 

 gravity would remain the same as that of normal 

 milk. 



The fats.— The fat of milk, or butter fat, as it 

 is often called, is a mixture of a considerable number 

 of separate and distinct fats, no less than six or 

 eight being normal to milk, and a considerable fur- 

 ther number may be present under various conditions. 

 The fats in milk are of two kinds, volatile and non- 

 volatile. To the former class belong the various 

 normal essential oils that give to milk and butter 

 their characteristic odors and flavors, and in addition 

 to these normal fats there may be a large number 

 of volatile oils that are present in the food of the 

 cow, and that impart to the milk the characteristic 

 flavors of such foods. 



The volatile fats.— The volatile fats make up only 

 a small part of the total milk fat ; in general, prob- 

 ably about 15 per cent of the whole. The chief 

 normal volatile fats are butyrin, caprin, caproin, 

 caprilin and laurin. Of these, butyrin is in much 

 the largest proportion and of much the greatest im- 

 portance. It is the chief volatile fat of milk and 

 butter, and to it are due in large part the character- 

 istic flavors and aromas of milk and butter. ButjTin 

 readily decomposes, forming butyric acid, which is the 

 chief element in the rancid or " frowy " taste that 

 butter acquires upon long standing. 



