PASTEURIZATION 197 



is agitated by means of a series of blades moving lengthwise 

 back and forth, or in the case of round tanks by a vertical, 

 rotating agitator. 



The other type of vat pasteurizers consists of the most 

 modern types of cream ripeners equipped with horizontal or verti- 

 cal revolving discs or coils which carry both the heating and the 

 cooling medium. This is the most widely used type of vat pas- 

 teurizer. The revolving discs have now been largely replaced 

 by the revolving coils, as the strain of steam, water and brine 

 pressure and the wide range of temperature proved too great 

 a tax on the discs. 



Fig*. 32. Jensen vat pasteurizer 

 . . . Courtesy J. G. Cherry Co. 



The coils in the vat pasteurizers vary somewhat in con- 

 struction, principle of feed and size, with different makes of 

 manufacture. 



In some vats of large size there are two coils side by side. 

 This makes possible the placing of the coils low down without 

 curtailing heating surface. This principle has the advantage 

 of keeping the coils submerged in the cream, which is desirable, 

 because it minimizes the beating of air into the cream, thereby 

 avoiding foaming and the tendency of oxidation of some of the 

 constituents of the cream, while the cream is hot. 



Most of the coils have a tube diameter of from two to two 

 and one-half inches and the diameter of the spiral ranges from 

 twenty-four to twenty-nine inches. 



The amount of heating and cooling surface per gallon of 

 cream varies with different makes and sizes of vats. In many 



