A DAIRY LABORATORY GUIDE 3 



named because they are made respectively from 

 volatile and nonvolatile fatty acids. 



The fats under each class are as follows: 



VOLATILE NONVOLATILE 



Butyrin Olein 



Caprin Myristin 



Caproin Palmatin 



CaprilHn Stearin 

 Laurin 



There is some dispute as to vi^hether laurin is a 

 volatile or nonvolatile fat, but it is usually consid- 

 ered volatile. The volatile fats compose about 8 

 per cent and the nonvolatile about 92 per cent of 

 butter fat. The fats of butter fat have different 

 characteristics and properties, and one chief dif- 

 ference of fats is their meltinq- point. For example 

 the meltine;' point of stearin is about 143" F., and 

 the meltinq- point of olein is al)out 40° F A \aria- 

 tion in the amoimt of either of these Iwn fats would 

 necessarily cause the meltin.c; point of butter fat to 

 vary. The melting point of butter fat is usually 

 between 92° F. and 96° F. 



Casein is the chief proteid compound of milk, and 

 forms about 20 per cent to 23 per cent of the milk 

 solids. It exists in milk in very fine suspension, 

 and is held in suspension by the salts of calcium. 

 It is, therefore, sometimes called calcium casein. 

 The casein is in such a fine state of suspension that 

 it cannot be filtered out of the milk by any ordinary 

 means. This fine state of suspension is called the 

 colloidal state, ^^'hen milk sours naturally and 

 enough acid is found to unite with the lime salts 

 of the milk, the casein is precipitated. Casein is 

 also precipitated by any acid and rennet or pepsin. 

 Casein is valuable as food both in raw milk and in 



