CHAPTER VI. 



SEPARATION OF CBEAM. 



Cream is that part of milk into which a large 

 portion of its fat has been gathered. It is com- 

 posed of the same constituents as milk, but they 

 are not in the same or any constant relative pro- 

 portion. Cream is separated from milk to be con- 

 sumed as food, and, as a matter of convenience, in 

 the manufacture of butter. The separation of cream 

 is always attended with some loss of fat. The per- 

 centage of fat in cream may vary anywhere between 

 8 and 70 per cent. Cream of good quality for com- 

 mercial purposes should contain from 18 to 25 per 

 cent of fat, and very rich cream contains from 35 to 

 40 per cent of fat. Cream is composed of glob- 

 ules of fat, with such part of the water and solids 

 as adhere to them. Its separation from the milk 

 is effected by means of the difference in specific 

 gravity between the globules of fat and the milk 

 serum. The fat in the milk is in the condition 

 known as an emulsion ; that is, in the form of minute 

 globules, which are kept from running together and 

 coalescing by means of the surface tension of their 

 particles and the viscosity of the liquid in which 

 they float ; therefore, any condition of the milk 



G (97) 



