946 



Journal of Agricultural Research 



Vol. VI. No. 24 



It has been indicated in the foregoing experiments that the quantity 

 of carbon dioxid occurring in the gas inclosed in a package of stored 

 butter is proportional to the amount of nonfatty ingredients incorporated 

 into the material. There is also a more or less pronounced decrease in 

 the oxygen content during the storage period. The following additional 

 experiment was made with the view of confirming this relative change in 

 the percentages of carbon dioxid and oxygen, and especially to determine 

 the quantities of these gases occurring in unwashed butter at the time of 

 its manufacture, since all the above-described analyses were made upon 

 the samples after an interval of two months in storage. 



For this purpose some unwashed butter was prepared from cream 

 pasteurized at 145 F. for 20 minutes, and, as in the other cases, ripened 

 with a pure culture. The cream was ripened to an acidity of 0.45 per 

 cent (calculated as lactic acid), cooled to 7 C. (44. 6° F.), held overnight, 

 during which the acidity rose to 0.67 per cent, and then churned. The 

 buttermilk was drawn off and the butter allowed to remain unwashed. 

 The butter was then salted with chemically pure salt and worked on a 

 table worker. This butter contained 4.72 per cent of sodium chlorid and 

 0.56 per cent of protein (total NX6.38). The butter was then packed 

 into the special glass tubes for air analysis. 



The gas in the first sample was extracted therefrom and analyzed as 

 soon as possible after the butter was made — that is, \ l / 2 hours. The 

 remaining samples were kept at room temperature, but in the dark 

 (Table XVIII). 



Table XVIII. — Analysis of air from a second sample of unwashed butter kept at room 



temperature but in tlie dark 



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

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



Most of the carbon dioxid appears to have existed in the butter as 

 soon as the manufacture of the material was completed. It also ap- 

 pears to increase somewhat in quantity during a period of two weeks. 

 The oxygen figures show in a striking manner the decrease in the in- 

 itial quantity of this gas present in the butter, and it is apparent that 

 it has decreased to practically one-half this quantity after being kept 

 two weeks at room temperature in the dark. 



