COMPOSITION OP MILK. 13 



by melting a sample of butter which contains these different 

 fats, the fats with a low melting-point would melt first, and 

 leave the remainder in an unmelted condition. Such is not 

 the case. Butter-fat in this respect behaves a good deal hke 

 different metals with different fusing-points. When they are 

 melted and mixed together, cooled and then remelted again, 

 they assume a common melting-point. It is the same way 

 with butter-fat. It melts at a temperature of 91° to 

 96° F. 



As the body temperature of cows (about 101° T.) is above 

 this temperature, the fat globules are present in the milk in 

 hquid form when milk is first drawn. A peculiarity about 

 these fat-globules in milk is that the milk and fat may be cooled 

 down below the melting-point of the fat of butter without 

 the fat-globules in milk being solidified. It requires a tem- 

 perature of between 60° and 78° F. before the fat-globules 

 in milk begin to solidify. When these small fat-globules are 

 caused to unite, as during the churning process, they solidify 

 at higher temperature. This behavior of the fat in milk evi- 

 dently must be due to a relative change in the position of the 

 molecules of fat during the process of cooling and warming. 

 No definite explanations, so far as is known, have been given 

 for this condition of the fat. 



The non-volatile fats found in butter-fat are practically 

 the same as those found in other animal fats. 



Composition of Butter-fat. — In his " Dairy Chemistry," 

 Richmond gives the following composition of butter-fat, repre- 

 senting the mean results obtained by different observers: 



Fat. 



8% Volatile. 



92% Non-volatile. 



Butyrin 3.85% 



Caproin 3 . 60% 



L Caprylin. 55% 



Caprin 1.9% 



Laurin 7 . 4% 



. Myristin 20 . 2% 



Palmitin 25.7% 



Stearin 1.8% 



Olein 35% 



