sept, ii, 1916 Progressive Oxidation of Cold-Storage Butter 941 



From the above-mentioned data it will be seen that but a slight oxida- 

 tion of the fat occurred during a storage interval of more than three 

 months at a temperature of 32 ° F., even when the sample was kept under 

 conditions decidedly more favorable, in comparison with the preceding 

 one, to permit any pronounced oxidation. It would appear, therefore, 

 that any oxidation of pure butter fat kept in storage at a temperature of 

 o° F. for a reasonable length of time, if it occurs at all, must be extremely 

 slight. The results of experiments already conducted, however, have 

 shown that a progressive oxidation in whole butter ma}>' occur while held 

 in storage at a temperature of o° F. 



The question, therefore, arises whether there occurs an oxidation pro- 

 gressing in some one or more of the nonfatty constitutents of whole butter. 

 In the attempt to clear up this point the following experiments were 



conducted. 



OXIDATION OF NONFATS 



The butter samples used in the two following experiments were made 

 in the experimental creamery at Troy, Pa., from the same lot of cream 

 as was the preceding sample of butter fat stored at a temperature of o° F- 

 The cream was pasteurized in a continuous pasteurizer at a temperature 

 of 165 F., and was ripened with a pure culture. The acidity of the 

 cream at the time of churning was 0.40 per cent (calculated as lactic 

 acid). The butter in the churn was washed until the wash water was just 

 clear. One half of the butter in the churn was removed and was desig- 

 nated as " normally washed butter." The other half, which remained 

 in the churn, was now given an additional copious washing in four 

 changes of water and designated as "excessively washed butter." 



The sample designated in the experiments as "unwashed butter" was 

 prepared from a different lot of cream, which was pasteurized and 

 ripened under the same conditions as indicated above. It was ripened 

 to an acidity of 0.51 per cent (calculated as lactic acid), cooled to j%° C. 

 (45. 5 F.), held overnight, during which the acidity rose to 0.65 per cent, 

 and then churned. The buttermilk was drawn off and the butter 

 allowed to remain unwashed, so as to contain the greatest amount of 

 nonfatty ingredients of all three samples. 



Since it was desired to have the three foregoing samples differ from one 

 another only with respect to their buttermilk content, care was taken 

 to prepare them otherwise in identically the same manner. Each was 

 worked on a table worker to the extent of 40 revolutions, to incorporate 

 a large quantity of air. They were then packed in clean and sterile 

 glass jars, and also in the special glass tubes for air analysis. The butter 

 in the jars was covered with a thin layer of paraffin to exclude any action 

 of the atmosphere other than that confined within the material itself. 



The appearance of undesirable flavors in stored butter has often been 

 attributed to the use of either impure salt or water, or both, so this con- 

 tingency was avoided by the use, in all cases, of chemically pure sodium 

 chlorid and distilled water. 



