PASTEURIZATION 209 



If the pasteurizer is in poor condition, rusty, or with the tin 

 worn off and the exposed copper unclean and coated with ver- 

 digris, etc., the damage done to the cream and butter may be 

 far greater than the possible benefits of pasteurization. The 

 direct exposure of the cream to iron and copper and their salts 

 tends to give the finished product a disagreeable metallic flavor. 

 The acid in the cream enters into chemical combination with 

 such metals as iron and copper, forming metallic salts, such 

 as iron lactate and copper lactate. These salts have the power 

 to accelerate bacterial action in butter and also to stimulate 

 oxidation and decomposition of its ingredients. In the presence 

 of pasteurizing heat this chemical action is intensified. The 

 action of these metallic salts is made more damaging by the 

 fact that they possess catalytic properties, that is they continue 

 to act, changing the substances (fats, curd, etc.) with which 

 they come in contact, without they, themselves, (the salts) being 

 changed or weakened. Metallic salts have been found to con- 

 stitute important members of the combination of conditions 

 that produce butter with metallic, tallowy, fishy, and other 

 flavor defects. 



Immediately after use the pasteurizer should be rinsed out 

 with water. In the case of the flash machine the water can be 

 pumped through the pasteurizer immediately following the 

 cream. The machine is then opened, the agitator or drum care- 

 fully removed and all parts are scrubbed with brush and hot 

 water containing non-caustic washing powder. Some operators 

 prefer to fill the flash pasteurizer with alkali solution, allow it 

 to soak over night and then complete the cleansing the follow- 

 ing morning. It has also been found that the coating on the 

 heating surface of flash machines can be readily removed by 

 charging the jacket with steam, after the pasteurizer has first 

 been rinsed with water. This heating causes the coating to 

 dry, contract and peal off, facilitating its removal. 



The vats are best filled one-third to one-half full with 

 hot water containing non-caustic washing powder and the sides, 

 bottom, coil, shaft and gate are scrubbed with a good brush until 

 all remnants of cream are removed. If the vat pasteurizer has 

 been operated in the proper manner, avoiding the blowing of 

 steam direct into the coil, there is little danger of a coating of 



