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



939 



These figures would seem to indicate that very little, if any, chemical 

 change occurred in the fat after having been kept in storage at a tem- 

 perature of o° F. for a period of four months, and it was so apparent 

 that no pronounced change could be expected until a longer time had 

 elapsed than is usually practiced in storing butter that this experiment 

 was discontinued. It was apparent from the analysis of the fat that 

 no noteworthy oxidation had occurred therein while the experimental 

 samples were held in storage. An analysis of the air confined within 

 the butter fat is given in Table VI. 



Table VI. — Analysis of the air in butter fat, stored at 0°F., after being nearly freed 

 from the nonfatty ingredients by melting, filtering, and washing 



[Protein, 0.05 per cent; total N X, 6.38; calculated to 0° C. and 760 mm.] 



Months. 



3 •■ 



4- • 

 5-- 

 12. 

 24. 



Total gas. 



C.c 



33- 20 

 27-35 

 29- 5i 

 38.90 

 30.81 

 3i-59 



Total carbon dioxid. 



O.99 



•94 



•93 



1-38 



1. 76 



•93 



Per cent. 

 2.98 

 3- 44 

 3- *5 

 3-55 

 5-7i 

 2.94 



Total oxygen. 



6-43 

 5. 22 



5-94 

 7-63 



4. 27 



•93 



Per cent 



19 

 19 

 20. 

 19 

 13 



94 



Calculated 

 oxygen. 1 



C.c. 



6.44 



5. 28 

 5- 72 

 7-5i 

 5- 81 



6. 13 



1 After deducting the figure for carbon dioxid from total quantity of gas extracted from the tube, and 

 assuming that the residual gas is pure air — that is, approximately one- fifth oxygen. 



Practically all the carbon dioxid present in the gas extracted from 

 these samples was evidently either in the butter fat at the time of its 

 manufacture or was produced therein within a period of two months 

 after being put into storage. Although the figures would seem to 

 indicate a slight progressive increase in its amount during the storage 

 interval, yet its total amount is small; and in view of the oxygen data 

 obtained it seems to bear little or no relation to the oxygen content. It 

 is very clear, however, that no appreciable oxidation of the nearly pure 

 fat itself occurred during a storage interval of five months; and it was 

 not until after the sample had remained in storage for one year that a 

 slight, measurable oxidation was indicated. In this connection it is 

 thought advisable to note the following general consideration: 



Although the iodin numbers obtained for the first and second months 

 and those obtained for the third and fourth months are so close as to 

 resemble duplicate determinations, yet we will take it for granted that 

 the total decrease in the iodin number during the entire period of the 

 investigation is attributable exclusively to the absorption of oxygen by 

 the olein of the fat and not to some one or more of the other factors 

 which, as already indicated earlier in this paper, may influence the data 

 obtained for the iodin number. If we regard 0.72 (the difference between 

 37.30 and 36.58) as representing the taking up of oxygen by the olein of 

 the fat, the following calculations, based upon this hypothesis, will serve 

 to point out the great improbability of any change in the fat from oxi- 

 dation during storage at a temperature of o° F. 



