COMPOSITION AND PROPERTIES OF BUTTER 533 



Soluble or Volatile Fats and Insoluble or Non- Volatile Fats. 



The milk fats are spoken of as soluble or volatile and insoluble 

 or non-volatile fats. In reality none of the fats are soluble or 

 volatile, but the fatty acids of some of the fats or glycerides, 

 when, as the result of the decomposition of the respective glyc- 

 erides, they become separated from their base, the glycerol, be- 

 come soluble and volatile. 



Some of the fatty acids are wholly soluble and volatile, to 

 these belong the butyric acid and the caproic acid ; others are 

 only partly soluble and volatile, to them belong the caprylic, 

 capric and lauric acids; still others are entirely insoluble and 

 non-volatile, to these belong the oleic, palmitic, myristic and 

 stearic acids. 



Of the total milk fat about 8 to 12 per cent yield volatile 

 and soluble fatty acids, while the remainder of 88 to 92 per cent 

 are insoluble and non-volatile s 



It is generally accepted, though by no means fully experi- 

 mentally proven, that the volatile fatty acids, of which the 

 butyrin is the most important, give the dairy products their 

 characteristic odor and flavor and that they derive from the 

 feed of the cows the characteristic feed flavors. Storch holds 

 that it is the slimy, nitrogenous film which he claims surrounds 

 each fat globule, that contains and is responsible for the char- 

 acteristic flavor and aroma of butter. 



Melting Point of Milk Fats. The melting point of the mixed 

 milk fat ranges between about 90 and 99 degrees F. and the solidi- 

 fying point ranges betwen 65 and 75 degrees F. Fleischmann 1 

 gives the melting point at 31 to 36 degrees C. (87.8-96.8 degrees 

 F.) and the solidifying point at 19-24 degrees C. (65-75 de- 

 grees F.). The several fats or glycerides of which the milk fat 

 is composed, differ from one another largely in their melting 

 points and in their solidifying points, and since the melting point 

 and the solidifying point of the fat control the mechanical firm- 

 ness or softness of butter, this fact is of the greatest importance 

 in the art of buttermaking. The melting points of the several 

 more important fats contained in milk are as follows : 



iFleischmnnn Das Buch der Milchwirtschaft, 1901. 



