72 EXPERIMENT STATIOlSr EECORD. 



From a study of proteolysis in storage butter, determined by different 

 methods and including a proposed method described in detail, it was evident 

 that proteolysis did not take place to any appreciable extent in the samples 

 studied, nor was there any relation between the figures for nitrogen and the 

 butter scores. Buttermilk from sweet, unpasteurized cream and from sweet, 

 pasteurized cream when preserved with 18 per cent sodium chlorid to corre- 

 spond to butter curd solution showed no proteolysis during a long period in cold 

 storage. Sodium chlorid did not inhibit proteolysis in sterilized skim milk 

 stored at 20° F. ( — 7° C. ). if a large quantity of proteolytic enzyms of bacterial 

 origin was present. Butter made from sweet, pasteurized cream kept better 

 than butter made from similar cream without pasteurization, but the changes 

 in unpasteurized cream butter could not be produced by reinoculating the 

 pasteurized cream with the bacteria of the cream before pasteurization. 



A preliminary report is made of a study of the possible oxidation of butter 

 by inclosed air. About 10 per cent by volume of fresh butter was found to be 

 a gas consisting approximately of nitrogen 33 per cent, oxygen 20 per cent, and 

 the remainder gases absorbable by sodium hydroxid. The percentage of oxygen 

 was materially less after storage. Overworked butter did not contain any 

 more air than that which had been normally worked. 



In studying the effects of metals, known amounts of iron were added to 

 cream, and although there seemed to be no definite relationship between the 

 amount of iron added to cream and the amount found in butter, buttermilk, 

 and wash water, yet a relatively small part of the iron went into the butter 

 as compared with the buttermilk, which seemed to take most of the iron, and in 

 which the presence of the flavor due to the iron was most noticeable. The 

 addition of iron to cream, even in as small an amount as 1 or 2 parts per 

 .million parts of cream had an influence on the flavor of the butter. Whenever 

 butter was made from cream which had stood in contact with iron rust it had 

 a peculiar taste and could be easily picked out from a lot of samples. 



" The cream may take up iron in quantities sufficient to affect the flavor from 

 rusty cans or even from the exposed bolt heads or other metal parts of the 

 churn. ... It was found that in milk to which 18 per cent sodium chlorid had 

 been added there was no change in the lactose when iron was added and a cur- 

 rent of oxygen passed through the milk for 72 hours." This indicated that the 

 naturally occurring peroxidase could not utilize molecular oxygen for the oxida- 

 tion of lactose. 



On the assumption that organic peroxids might be formed in butter, and that 

 such peroxids might be used by the peroxidase present for oxidation, a few 

 experiments were made in which the polarization of skim milk was observed 

 before and after the addition of hydrogen peroxid, with and without iron. 

 There was an appreciable lowering in the polarization in mixtures containing 

 hydrogen peroxid and iron. The tentative conclusion drawn is that the lactose 

 was oxidized by the action of the peroxid and iron, and if there were peroxid 

 formation in butter such oxidation of lactose might take place there. In pres- 

 ence of lactic acid, or its combination with casein, the lactose present might be 

 inverted, and the iron and oxygen would have the entire storage period in order 

 to bring about the slight chemical changes that would cause an off flavor. Fer- 

 rous salts were more active in the production of a strong odor than ferric salts. 



The iodoform test was much stronger in distillates from milk containing 

 ferrous sulphate. " While these results do not prove that the iodoform was 

 obtained from oxidation products of milk protein, they do prove the possibility 

 of such oxidation. By distilling such mixtures under low pressure and at low 

 tempei'ature to remove the possible objection that the temperature of distilla- 



