930 Journal of Agricultural Research Vol. vi, no. 24 



view most generally held at the present time, and the more recent litera- 

 ture on the subject indicates that this phase of research is to be con- 

 tinued with no less abated interest. It is still unknown whether the 

 development of undesirable flavors in storage butter is dependent upon 

 an oxidation occurring in the fat itself or whether the milk sugar and 

 nitrogenous constituents of the curd are those components of the butter 

 most susceptible to oxidation. Approximately 10 per cent of the 

 volume of butter is air (9), and it is quite possible that, owing to the 

 oxygen of the air inclosed within the material, a slight and progressive 

 oxidation may take place in the interior of a package of butter. This 

 possibility, when considered together with the known fact that marked 

 and undesirable alterations in the flavor of butter during storage may 

 be brought about by acidifying the pasteurized cream from which the 

 butter is made (10), has suggested the idea that an examination of the 

 air inclosed within packages of butter differently prepared and in butter 

 fat alone might furnish some interesting data as to whetlftr the undesir- 

 able chemical changes occurring in stored butter are caused by a pro- 

 gressive oxidation in the fat itself or in some one or more of the nonfatty 

 ingredients. 



It was deemed advisable to pursue this line of investigation in a manner 

 not previously attempted, so far as known. Samples of pasteurized 

 sweet-cream butter, butter made from pasteurized cream to which lactic 

 acid had been added, and butter made from pasteurized cream to which 

 a starter had been added and which was churned at once, were prepared, 

 packed in glass tubes, and stored. Tubes from each lot were removed 

 from storage after certain intervals of time had elapsed and an analysis 

 of the air therefrom was made by means of the gas apparatus specially 

 designed for the purpose. (See fig. 1 and PL CXI.) It was hoped that 

 the analytical data so obtained would show some distinguishing features 

 between the three samples dissimilarly prepared, especially with respect 

 to the sample made from acid cream. It was also decided to make use 

 of the determination of the chemical constants of the pure butter fat 

 to serve merely as an indication as to whether any chemical alteration 

 of the fat through oxidation had occurred during the storage interval, 

 confirmed by the analysis of the air extracted from packages of butter 

 fat to determine whether the oxygen content therein is diminished during 

 the storage period. The data so obtained were used as a standard, and 

 the aim kept in view was to study the effect, if any, of the presence of 

 varying amounts of nonfatty constituents (protein, lactose, etc.) upon 

 the decomposition of the fat of butter and, in addition, to note whether 

 the presence of varying quantities of these substances in the butter 

 induced an alteration during storage in the composition of the air incor- 

 porated in the samples at the time of their manufacture. Samples of 

 pure butter fat and of butter containing varying quantities of buttermilk 



