108 MILK 



The Reichert-Meissl number is lowest in Holstein fat, next 

 higher in Ayrshire, and then follow Shorthorn and Jersey fat in 

 the order named. 



The variation in the iodin number is due to breed. In Short- 

 horn and Holstein fat it is higher than Ayrshire and Jersey fat. 

 High iodin numbers are usually coincident with low Reichert- 

 Meissl numbers. The saponification number of Koettstorfer 

 shows little variation, and the melting-point of fat is nearly the 

 same. 



Proteins: Jersey milk has a higher protein content than the 

 other kinds. Holstein milk has the smallest amount. This 

 shows that milk with high fat content has also a high protein per- 

 centage, but the two constituents do not increase in the same 

 ratio. 



The relation of the amount of casein to fat is about the same 

 as the relation of the total .protein to fat. Based on this fact, 



©fShorthorra f ) ( ) 

 ^" ^ i^sMre Holstein 



Fig. 25. — The relative size of fat globules (Eokles and Shaw). 



Van Slyke has worked out a formula for determining the amount 

 of casein in milk when the percentage of fat is known. If F. 

 represents the percentage of fat in milk, the casein can be found 

 by this formula: 



(F.— 3) by 0.4 + 2.1 = percentage of casein in milk. 



This formula gives the cheese maker a method for finding the 

 amount of casein in milk after the fat content has been deter- 

 mined. It does not hold good when the milk is derived from cows 

 in the last stages of lactation, since the protein is relatively high 

 at this period. Of course, the formula is not appUcable when re- 

 fined results are desired. 



Hart said that "the relation of casein to fat varies among ani- 

 mals of different herds and among animals of the same breed." 

 Eckles and Shaw found similar relations. The following figures 

 show the ratio between fat and casein: 



