4 DAIRY CHEMISTRY 



As previously stated, the fat in milk is not present 

 in solution, but in suspension in the form of minute 

 globules. These milk fat globules are about one five- 

 thousandth of an inch in diameter. A cubic milli- 

 meter of milk is estimated to contain from 2,000,000 

 to 4,000,000 fat globules, or a single drop from 

 100,000,000 to 150,000,000. Under the microscope 

 the fat globules appear grouped together in small 

 colonies. The size of the fat globules yaries (1) with 

 the breed and individuality of the animal, and (2) 

 according to the length of time the animal has been 

 in milk. When a cow is fresh, there is a smaller 

 number of globules, but the globules are larger ; 

 when the cow is well along in her milking period, the 

 globules are smaller but more numerous. The milk 

 from the Channel Island breeds is characterized by 

 large fat globules, while the milk from the lowland 

 breeds contains smaller globules. The fat globules 

 must be massed together and collected when butter 

 is made. The more completely they are recov- 

 ered, the greater will be the amount of butter 

 produced. 



The fat globules are simply solid masses of fat. 

 At one time it was believed that they were sur- 

 rounded by a membrane, and in churning it was 

 supposed that the membrane had to be broken before 

 the globules would mass. Recent chemical investi- 

 gations have shown that there is no membrane sur- 

 rounding the fat globules. The fat globules are 

 lighter than any of the constituents of the milk 



