PASTEURIZATION 



205' 



Table 36. Per Cent Micro-Organisms destroyed when Heated to 

 145 F. for 10, 15, 20, 30 and 40 Minutes, Respectively. 



(Averages of 21 churnings.) 



tains a plug of raw cream which fails to be heated properly and 

 which tends to recontaminate the cream in the churn. 



Blowing air into the cream, during the process of heating 

 is not recommended, except in the case of very poor cream 

 tainted with objectionable strong odors and flavors. This kind 

 of cream is often considerably improved by blowing, eliminat- 

 ing some of the objectionable odors, but butter from such cream 

 will at best be of low grade. 



Blowing air into cream of fair or good quality is objection- 

 able because the air, in the presence of heat invites oxidation and 

 jeopardizes the keeping quality of the resulting butter. The 

 blowing of the cream during pasteurization is undesirable also 

 because butter made from such cream is prone to have a mealy 

 body. This is largely due to the fact that the blowing retards 

 and prolongs the heating process, hardening the curd particles 

 to such an extent as to render them mealy. The prolongation 

 of the heating process as the result of blowing air into the 

 cream is due to the cooling effect of air on the cream and the 

 increased evaporation of moisture which absorbs additional heat 

 units. 



It is advisable to revolve the coil while the cream is being 

 held at 145 degrees F. in order to guard against the tendency of 



