sept, ii, 1916 Progressive Oxidation of Cold-Storage Butter 949 



SUMMARY AND CONCLUSIONS 



The composition of the air confined within a package of pasteurized 

 sweet-cream butter known to contain bacteria and made from cream 

 having an acidity of o. 1 1 per cent (calculated as lactic acid) showed little 

 or no variation from its original composition after successive periods in 

 storage, aggregating six months, at a temperature of o° F. A small 

 quantity of the buttermilk from butter made from pasteurized sweet 

 cream having the same low degree of acidity as the cream above men- 

 tioned, when exposed to the influence of a very large and confined surface, 

 of air, appeared to have little, if any, effect upon the original composition 

 of the air when the buttermilk was stored for nine months under like 

 conditions of temperature. A portion of this same sample of sweet-cream 

 butter when kept at a temperature of 32 F. showed a decided change in 

 the original composition of the inclosed air, a change which was still 

 further increased when the butter remained for a short time at room 

 temperature. This change in the composition of the air originally incor- 

 porated into the butter was expressed by a decrease in the percentage of 

 oxygen and a corresponding increase in the percentage of carbon dioxid. 

 This sample of sweet-cream butter still possessed a good score after six 

 months' storage at a temperature of o° F., there being no indication of 

 any undesirable flavor. 



The change in the composition of the air initially inclosed within a 

 package of butter made from sweet cream and churned immediately 

 after the addition of 15 per cent of a commercial starter showed but little 

 variation from that observed in the sample of sweet-cream butter when 

 the two samples were kept under comparable conditions, both being in 

 storage at a temperature of o° F., although the acidity of the cream in 

 the first case was somewhat higher (0.25 per cent) than that of the cream 

 from which the sweet-cream butter was made. This sample of butter 

 also displayed good keeping qualities during its storage period of nearly 

 seven months at a temperature of o° F. 



The composition of the air inclosed within a package of butter made 

 from sweet cream and churned immediately after the addition of lactic 

 acid, the total acidity of the cream being about six and one-half times 

 greater than that of the cream from which the sweet-cream butter was 

 made, showed pronounced variations from its original composition during 

 successive periods of storage at a temperature of o° F. These variations 

 were still greater when the sample was allowed to stand at a temperature 

 of 32 F. In this case there was a considerable and a progressive decrease 

 in the original oxygen content, as well as in the original carbon-dioxid 

 content. A small quantity of the buttermilk from butter made from 

 pasteurized sweet cream and churned immediately after the addition of 

 lactic acid, when exposed to the action of a very large and confined sur- 

 face of air under the same temperature conditions, showed precisely the 



