208 PASTEURIZATION 



With equipment of average capacity, there is no very 

 great saving in time by this combination pasteurizing process. 

 It requires about as much time to run the cream through the 

 flash machine as it does to heat the cream to the desired tem- 

 perature in the vat. The extra time needed to fill the vat, how- 

 ever, is eliminated, inasmuch as with this system the heating of 

 the cream and the filling of the vat are done in one operation. 



The chief advantage of this system lies in the preservation 

 of the vat. The cream being neutralized before it reaches the 

 vat avoids the corrosive action of the acid on the vat, and the 

 heating in the vat being eliminated minimizes further corrosion 

 and wear of the tin coating on coil and vat liner ; thereby render- 

 ing the cleaning of the vat easier. The bearings and stuffing boxes 

 in the vat are also saved from heavy wear caused by expansion 

 incident to heating in the vat. 



In some cases where the combined flash and holding pasteuri- 

 zation is in operation, the holding of the hot cream is done in 

 a compartment retarder in which it is held for the desired length 

 of time and from which it finally reaches the vat where it is 

 cooled. One objection to this system lies in the obvious danger 

 of recontamination of the cream by flowing into two containers 

 after pasteurization. When this system of pasteurizing is used, 

 special attention should be given to the proper cleaning and 

 steaming of all containers used after pasteurization. 



Cleaning and General Care of Pasteurizers. On the proper 

 cleaning and care of the pasteurizer depend very largely its 

 efficiency and its period of usefulness. Remnants of cream, neut- 

 ;ralizer or wash-water containing alkali, have a corrosive action 

 ,on the tin coating and cause this coating to wear off rapidly. 

 The use of tools that scratch the metal, such as wire dish cloths, 

 ;sand and emery paper, metal bristle brushes, etc., cannot be 

 too strongly condemned. Washing powders containing free 

 caustic substances, such as soda or potash lye, attack the metal 

 and should not be used. Dry or concentrated alkali of any 

 kind should not be allowed to remain on the tinned surface of 

 coils and vat. It is best to use only dilute solutions and rinse 

 off all traces of alkali after washing. 



