MILK FATS 31 



two fats, with myristin, make up about half of the 

 weight of the milk fats. 



33. Olein is quite different from either palmitin 

 or stearin. This fat makes up about 40 per cent 

 of the weight of butter. Under ordinary conditions 

 olein is a liquid. It solidifies at a temperature 

 of 40 F. It is liquid at the ordinary temperature 

 of the cold deep setting of milk, that is, the set- 

 ting of milk in ice water. Olein has the property 

 of readily and copiously dissolving palmitin and 

 stearin. The larger the per cent of olein in a butter 

 or fat, the softer it is. Sperm oil, cod liver oil, and 

 many of the vegetable oils are rich in olein. 



34. Butyrin melts at a temperature of 77 F. 

 Milk fats contain from 5 to 7 per cent of buty- 

 rin. Although it forms such a small proportion of 

 milk fat, it is the characteristic fat of butter. It is 

 the butyrin which gives to butter its individuality, 

 and its presence or absence is the distinguishing 

 point between butter and oleomargarine. Butyrin, 

 when decomposed, forms butyric acid. In rancid 

 and stale butter, the rank odor is due to butyric 

 acid. Butyrin is not as stable a fat as palmitin, 

 stearin, or olein. 



35. Caproin and Caprylin comprise only a small 

 part of the fats of milk, and they do not require any 

 special consideration. 



36. Glycerine and Fatty Acid Content of Fats. 

 When fats are broken up into simpler products, 

 glycerine is one of the substances formed ; the other 



