BUTTER DEFECTS 497 



hydrolysis is only the initial phase of rancidity and that either 

 the free fatty acids, or the glycerol, or both, undergo further de- 

 composition yielding products which produce and intensify ran- 

 cidity in butter, and this further decomposition must of neces- 

 ity be an oxidation. 



In the case of the saturated fatty acids, the action would be 

 only very slight and if at all, it would probably be of enzymic 

 nature. The unsaturated fatty acids, of which the oleic acid 

 is representative, yield more readily to oxidation. They may 

 be oxidized forming fatty acids of higher molecular weight, 

 such as acids of the hydroxy series. Or they may be broken 

 down to acids of lower molecular weight, forming various fatty 

 acids such as pelarg-omc, azelaic acid, etc., which may produce 

 or intensify the rancid odor and flavor. Also aldehydes formed 

 by the breaking down of oleic acid may play a part in the pro- 

 duction of rancidity ; this possibility, however, Lewkowitsch does 

 not consider probable. That the oxidation of the free fatty acids 

 plays a considerable role in the production of rancid butter, is 

 therefore very probable, and is emphasized by the fact that 

 exposure of the butter to air, especially in the absence of re- 

 frigeration, and in the presence of light which intensifies oxida- 

 tion, greatly hastens the development of rancidity. Allen 2 also 

 holds that oxygen and light play a considerable part in the 

 chain of factors instrumental in the production of rancidity. 



Again it is possible that the free glyverol, resulting from the 

 hydrolysis of the fats, and which in itself is neutral, odorless 

 and tasteless, may yield to oxidation, forming acids and alde- 

 hydes, many of which have a very pungent odor resembling ran- 

 cidity. Browne 1 attributes the pungent, irritating odor which 

 all rancid fats give off, especially on being warmed, to the de- 

 composition (oxidation) of free glycerol, forming acrolein. He 

 found a decrease in the percentage of glycerol of all fats when 

 they become rancid, the decrease being proportional to the ran- 

 cidity of the samples. 



Furthermore, the lactose of butter, upon oxidation, may 

 assist in the development of products, similar to those result- 



1 Allen, Commercial Organic Analysis, Vol. II, 1912, p. 313. 

 8 Browne, A Contribution to the Chemistry of Butterfat, Jour. Amer. 

 Chem. Soc. Vol. 21. 1898. 



