PASTEURIZATION. 179 
more readily than milk containing less air. If pumps are used 
for pumping the milk, it is well to admit as little air into the 
milk as possible. This can be accomplished by keeping plenty 
of milk in the tank which feeds the pump, or by having a float 
which will close the inlet to the pasteurizer as soon as the tank 
is emptied. If the speed of the agitator in the pasteurizer 
is great enough, the scum is forced towards the center. For 
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Fig. 119.—The Jensen pasteurizer. 
some time it was thought that only the best sweet milk could 
be pasteurized by the intermittent process of pasteurization. 
It is well known that when a sample of milk reaches a certain 
degree of acidity it coagulates upon heating. It was thought 
that by the continuous method of pasteurization this would 
interfere with getting proper results. Experiment, however, 
shows that the coagulated sour cream and milk can be suc- 
cessfully pasteurized, but it is still a fact that the better con- 
dition the milk or cream is in, the easier it can be pasteurized 
