CHEMICAL PKOPEUTIES OF FATS AND OILS 283 



increase in imsaponifiable fraction takes place, and finally a stable per- 

 oxide results. According to Engler and Weissberg (cited by BulP^'), an 

 intermediate moloxide is first formed, which is then changed into the stable 

 peroxide. These reactions for oleic acid are illustrated below. 



A 



CH3(CH2)7CH:CH(CH2)7C00H — •- CH3(CH2)7C-C (CHsItCOGH 



H H 



Oleic ;ici(l Oleic acid moloxide 



0-0 



> CH3(CH2)7C-C(CH2l7COOH 



H H 



Oleic acid peroxide 



It is generally believed that this type of peroxide can act as an oxygen 

 carrier. It can bring about the oxidation of some of the fat components 

 such as the unsaturated acids and the fat-soluble vitamins. Linoleic acid 

 is more readily attacked than oleic acid,*^^'^'^ while linolenic acid has a 

 still greater susceptibility to oxidation. ^^'* Fats composed of fatty acids 

 having conjugate double bonds are especially reactive. Thus, pseudo- 

 elaeostearic acid containing the conjugate bonds is more susceptible to oxi- 

 dation than is isomeric linolenic acid, in which the double bonds are not 

 conjugated. *^^ It is believed that small amounts of conjugated acids are 

 present in edible oils, as judged by their absorption spectra.*'^ Such con- 

 jugate acids would be especially susceptible to the formation of peroxides 

 which may initiate reaction chains. Morrell and his group, ^"~^^^ as well 

 as Franke and Jerchel,**^ have carried out extensive research in which the 

 reactivities of various peroxides have been differentiated. 



(b) Hydrolytic Rancidity. This is also known to occur. Hydrolysis, 

 however, is not a necessary concomitant of rancidity. Kerr and Sorber*'^ 

 believe that, in oxidative rancidity, the failure to demonstrate glycerol or 

 free acids indicates the absence of hydrol3''sis. In the case of dairy prod- 

 ucts, butyric and other low molecular weight fatty acids are set free by 

 hydrolysis, which usually results from the action of lipase. The odors of 



^'2 K. Tiiafel and A. Seuss, Fettchem. Umschau, 41, 107-113, 131-137 (1934); Chem. 

 Abst., 29, 369 (1935). 



«' G. E. Holm, G. R. Greenbank, and E. F. Deysher, Ind. Eng. Chem., 19, 156-158 

 (1927). 



*'^ R. Kuhii and K. Meyer, Z. physiol. Chem., 185, 193-216 (1929). 



*^ J. P. Kass and G. O. Burr, J. Am. Chem. Soc, 61, 3292-3294 (1939). 



«6 E. S. Miller, W. R. Brown, and G. O. Burr, Oil & Soap, 15, 62-65 (1938). 



"' R. S. Morrell and S. Marks, J. Soc. Chem. Ind., 50, 27-36T (1931). 



^» R. S. Morrell and W. R. Davis, J. Soc. Chem. Ind., 55, 237-246T (1936). 



«» R. S. Morrell and W. R. Davis, /. Soc. Chem. Ind., 55, 261-265T (1936). 



**° R. S. Morrell and W. R. Davis, /. Soc. Chem. Ind., 55, 265-267T (1936). 



^" R. S. Morrell and E. O. Phillips, /. Soc. Chem. Ind., 58, 159-162T (1939). 



*« W. Franke ami D. Jerchel, Ann. .533, 46-71 (1937). 



