240 CREAM RIPENING 



this respect, vats equipped with agitators of horizontal or vertical 

 motion are preferable to the rotary agitators, such as the discs 

 and horizontal coil, but the former are slower in their tempering 

 action than the latter. There are some coil vats on the market 

 now in which the coil is vertically suspended, removing the glands 

 and bearings entirely from contact with the cream. 



Effect of Copperlined Vats on Quality of Butter. From 

 the standpoint of material of construction it should be thor- 

 oughly understood, that the cream ripening vats, now in gen- 

 eral use in this country, are unsuitable and highly objection- 

 able, because the metal, copper, with which they are lined, con- 

 stitutes one of the most active agencies that invites chemical 

 decomposition of one or more of the constituents of cream and 

 butter and thereby impairs the flavor and deteriorates the keep- 

 ing quality of butter, as has been conclusively shown by Hun- 

 ziker and Hosman 1 who demonstrated that copper, alloys of 

 copper such as brass and german silver, and copper salts, acting 

 as powerful-oxygen-carriers and catalizers, are capable of intro- 

 ducing oxidation in butter that is most disastrous to its flavor 

 and keeping quality. Iron also has a specific catalytic action 

 which aids the oxidation process, but in the case of iron bases 

 and salts this action is relatively slight. Tin and nickel are 

 practically inert, exerting no appreciable oxidizing influence. 



In the earlier days of butter manufacture, the lining of 

 the cream ripening vats consisted of tinned sheet iron. The 

 tin coating on the iron lining is relatively permanent. It stays 

 bright as long as the vat lasts. These vats, however, were 

 jacketed vats and the lining was prone to rust. The rusting 

 did not usually occur on the inside of the vat lining that was 

 exposed to the cream. The lining rusted on the jacket side, 

 because of the continued exposure of the lining to the damp- 

 ness in the jacket. 



From the standpoint of their effect on the quality of the 

 cream these old-fashion, iron-lined, tinned, jacketed ripening 

 vats were not objectionable. So long as the lining did not rust 

 through from the outside, the tin coating remained on the sheet 

 iron and was bright. But these vats were of comparatively short 



1 Hunziker and Hosman, Tallowy Butter Its Causes and Prevention, Journal 

 of Dairy Science, Vol. L, No. 4, 1917. 



