sept, ii, 1916 Progressive Oxidation of C old-Storage Butter 929 



rancidity may have appeared in a stored fat without the manifestation 

 of any increased acidity as measured by a simple titration. Again, an 

 undue significance may be attached to a slight decrease in the original 

 iodin number of the fat. Such a decrease is usually considered to be 

 caused by the taking up of oxygen by the double bond of the unsatur- 

 ated glycerid; yet it must be remembered that self-polymerization — the 

 interlocking of two or more molecules of the unsaturated glycerids — may 

 occur, a condition which would likewise bring about a lowering of the 

 iodin value. Again, the olein of butter fat may not exist entirely as the 

 normal glycerid, and it is possible that a certain amount of this glycerid 

 may occur as an isomerid. So far as is known to the writer no work 

 has been carried out to determine whether the olein of stored butter is 

 present entirely as the normal glycerid. In this connection it may be 

 observed that the work of Ponzio and Gastaldi (8) and of Fokina (1) 

 indicates that the farther the double bond is removed from the carboxyl 

 group the nearer the iodin number approaches the theoretical value. Nor- 

 mal oleic acid gave the theoretical value of 90. On the contrary, 2-3 oleic 

 acid gave a Hiibl number of only 6.6, Wijs 20.4, Hanus 1.9. While there 

 are no data at hand at present to prove that 2-3 oleic acid actually does 

 occur in butter fat, yet this contingency is quite possible; and it is well 

 to take it into consideration as yet another factor which may produce a 

 slight lowering of the iodin number of stored butter. It is evident, how- 

 ever, that the customary methods in vogue to determine the quality of 

 fat leave much to be desired. 



One of the factors so often construed as influencing the appearance of 

 undesirable flavors in a fat is the nature of the impurity, or impurities, 

 contained therein. In just what manner these foreign substances bring 

 about these undesirable characteristics has not been fully cleared up, 

 because it is conceivable that it depends upon several parallelly pro- 

 gressing chemical reactions and because it is possible that slight chemical 

 changes really difficult of identification by analytical methods suffice 

 to produce the above-mentioned disagreeable features. 



It is apparent that even at the present time there seems to be con- 

 siderable doubt as to whether the undesirable flavors of storage butter 

 arise from a decomposition occurring in the fat itself or in some one or 

 more of the other components entering into the composition of the whole 

 product. For this reason it is thought advisable to confine the prelimi- 

 nary work on this subject to an attempt to settle this most basic consid- 

 eration before proceeding with the further investigation of the causation 

 of the "off flavors'" so frequently met with in storage butter. 



STATEMENT OF THE PROBLEM AND METHOD OF SOLUTION 



Even in those times when the chemical constitution of the fats was 

 still unknown it had been surmised that the changes which oils and fats 

 underwent on keeping were simply the result of oxidation. This is the 



