192 PASTEURIZATION 



raise the cream, the faster must be the speed of the pasteur- 

 izer. This high speed tends to cause the liquid fat globules 

 at the high pasteurizing temperature to become distorted, dis- 

 turbing the thin surface layer of adsorbed concentrated serum, 

 which protects them, and exposing a larger surface of the fat 

 to objectionable influences, such as the oxidizing action of 

 light, air, heat and metals. Excessive speed therefore may, 

 under certain conditions, result in serious butter defects. 



For tfre same reason it is undesirable also to try to force 

 more cream through the pasteurizer than its rated capacity. 

 The amount of cream the pasteurizer is capable of taking care 

 of depends on the speed of the agitator. The higher the speed 

 of the agitator the more cream can be made to pass through 

 the machine in a given length of time. The flash pasteurizers 

 are usually furnished with specific directions as to capacity per 

 hour and speed of agitator or revolving drum, needed to yield 

 the rated capacity. It is unwise to force more cream through 

 the machine than the rated capacity and speed call for, by 

 speeding up the agitator. If faster work is desired, the instal- 

 lation of a larger machine, or an additional machine, will 

 accomplish the purpose without injury to the butter fat. Forc- 

 ing the machine, aside from its unfavorable effect on the fat 

 globules, also usually diminishes the pasteurizing efficiency. 



Temperature Control. In all flash or continuous pasteur- 

 izers the regulation of the temperature needs constant atten- 

 tion in order to make possible uniform heating of all the 

 cream that flows through the pasteurizer. Unless the operator 

 supervises the operation of the pasteurizer from start to 

 finish, reliable results need not and should not be expected. 

 The ease of temperature control varies widely with different 

 makes of machines, as well as with such ever-varying factors 

 as temperature of the cream in the forewarmer, mechanical con- 

 dition of the cream,, uniformity of cream inflow, uniformity of 

 steam supply and uniformity of speed of cream pump and 

 pasteurizer. 



In order to make possible and to facilitate temperature con- 

 trol, the cream in the forewarmer must have a constant tenv 

 perature, preferably about 90 degrees F., the cream pump feed- 



