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



947 



The question now arises whether there exists in the samples of butter 

 fat the same homogeneous distribution of air bubbles as in the case of 

 those samples of butter containing the varying quantities of nonfatty 

 ingredients, for it is conceivable that the air incorporated into the butter 

 fat may occur mostly in large pockets, while the other samples may 

 contain, in addition, a certain amount of the total air inclosed within 

 the particles of curd, lactose, etc. 



In the first case it is reasonable to suppose that a smaller surface of 

 material would be exposed to the influence of the air than in the second; 

 yet it is improbable that this would alter the basic facts, since the ana- 

 lytical data obtained in the experiments indicate that the particles of 

 nonfatty ingredients inclosing the air are more readily attacked by the 

 oxygen therein than the fat itself. However, to obtain further con- 

 firmatory data on this point — that is, that the nonfatty constituents of 

 butter are more readily attacked by the oxygen of the air incorporated 

 into the material than the fat itself — the following experiments were 

 conducted. 



BUTTERMILK EXPOSED TO A LARGE SURFACE OF AIR 



Several of the special butter tubes were filled with large fragments of 

 cracked and ignited pumice. The pumice of one lot of tubes was im- 

 pregnated with the buttermilk from butter made from pasteurized cream 

 acidified to 1 per cent with lactic acid before churning. The pumice of 

 each tube of a second lot was treated with 10 c. c. of a 1 per cent solution 

 of lactic acid. The tubes of these two lots were kept at a temperature 

 of ^2° F. At various times tubes from each were removed from storage 



and an analysis of the air in them was made, 

 tained are given in Table XIX. 



The analytical data ob- 



TablE XIX. — Oxidation of acid-cream buttermilk and of lactic acid exposed to the action 

 of a large surface of air at a temperature of J2° F. 



The change in the composition of the air in contact with the acid 

 buttermilk was very marked during a storage interval of only 26 days 

 when this sample was kept at a temperature of 32 F. From a total 

 percentage of 17.67 found to be present in the acid buttermilk when the 

 material was 4)4 days old, the oxygen content fell to zero during the 

 period between this time and 26 days. The carbon-dioxid content of 

 the buttermilk, initially small in quantity, rapidly increases to a maxi- 



