CHAPTER IX 
SEPARATION OF CREAM 
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 
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