950 Journal of Agricultural Research voi.vr.No.24 



same phenomena with respect to alteration in the original air composition. 

 The oxygen content of the confined air had entirely disappeared within 

 a month's time. The carbon-dioxid content, originally 2.37 per cent, 

 had increased to more than 34 per cent within the same interval, after 

 which time it had begun to decrease. The flavor of this butter, which 

 was prepared from pasteurized sweet cream and churned immediately 

 after the addition of lactic acid, was somewhat unclean after a storage 

 period of only three months at a temperature of o° F., and decidedly 

 so after being in storage for six months under the same conditions. 



Further, it has been indicated by the investigation pursued with 

 pasteurized, ripened-cream butter through the successive steps from 

 nearly pure butter fat to samples of butter containing varying quantities 

 of ingredients other than fat and, finally, to samples containing the 

 greatest quantity of protein, lactose, etc., and stored for a reasonable 

 length of time (six months) at a temperature of o° F., that the amount 

 of carbon dioxid inclosed in a package of the material is directly pro- 

 portional to the quantity of these ingredients contained therein. It 

 has been shown that this quantity of carbon dioxid may increase during 

 the earlier part of the storage period, followed by a decrease during the 

 latter part. It is also of especial significance, perhaps, that the oxygen 

 content of the gas in the material undergoes a marked and striking 

 decrease during the interval that the samples of butter containing the 

 varying amounts of constituents other than fat are retained in storage, 

 and that this decrease is likewise proportional to the amount of acid and 

 ingredients other than fat contained in the butter. 



The fat of butter made from pasteurized cream, on the contrary, under- 

 goes no apparent oxidation during the same storage period when kept at 

 a temperature of o° F. It is only when a substance like pumice, which 

 may have catalytic properties, is impregnated with a small amount of 

 butter fat and exposed to the action of a large amount of air while kept 

 at a temperature of 32 ° F. that a very slight oxidation is noticeable. 



The results of the investigations may be summed up as follows: 



(1) The development of undesirable flavors in butter held in cold 

 storage at a temperature of o° F. is not dependent upon an oxidation of 

 the fat itself. 



(2) The production of "off flavors" so commonly met with in cold- 

 storage butter is attributable to a chemical change expressed through a 

 slow oxidation progressing in some one or more of the nonfatty sub- 

 stances occurring in the buttermilk. 



(3) The extent of this chemical change is directly proportional to the 

 quantity of acid present in the cream from which the butter was prepared. 



(4) The quantity of carbon dioxid present in cold-storage butter 

 appears to have a certain relation to the quantity of buttermilk in the 

 butter. During storage this quantity of carbon dioxid may increase to 

 a maximum followed by a progressive decrease. 



