METHODS Oi* SEPARATING CREAM 23l 



breeds of cattle ; thus, they are considerably larger in 

 the milk of the Jersey and Gruernsey than in the milk 

 of the Ayrshire or Holsfcein breeds. The Devons and 

 Shorthorns hold an intermediate position. The large 

 globules diminish in number as the time from calving 

 increases. The fat of the milk globules, in a solid 

 state, has a specific gravity of '930, and in a liquid 

 state, '912 ; the serum in which the globules float has 

 a specific gravity of about 1'038. The globules thus 

 tend to rise to the surface, where they form a layer of 

 cream. The rapidity of rise is greatest while milk is 

 cooling, as the globules then still contain liquid fat. 

 The largest globules are the first to rise, the smallest 

 may never rise at all. The smaller is the globule the 

 larger is its surface in proportion to its volume, and 

 the greater the resistance to its rise. Milk containing 

 an abundance of large globules is best for butter- 

 making, as the cream then quickly and perfectly 

 separates ; but milk with small globules is probably 

 best for cheese-making, as a more even distribution of 

 fat throughout the curd is then obtained. 



Methods of Separation. — Milk, when it leaves the 

 cow, will have a temperature of about 90° Fahr. ; if 

 set for cream it should be cooled as quickly as 

 possible, as changes in composition would rapidly 

 occur at a high temperature. Milk is often set for 

 cream in shallow vessels, the depth of milk being 

 perhaps three inches ; in these vessels the milk stands 

 for thirty-six to forty-eight hours till the cream has 

 risen. Under these conditions a large surface is 

 exposed, the milk receives a great number of bacteria 

 and moulds from the air, and a maximum amount of 

 change takes place: the result is a decomposition of 



