232 III. DIGESTIBILITY OF FATS 



erides or as ethyl esters. No increased output of fecal fat was observed 

 after a-methylmyristic acid was fed. However, after the administration 

 of a-ethylmyristic acid, there was a significant increase in fecal fat, while 

 the administration of a-propylmyristic acid produced an added augmenta- 

 tion in fecal fat. The effect resulting from a-butyl acids was similar to 

 that of the a-propyl acids. 



(6) The Effect of Polymerization 



It is known that, when fats are heated at a high temperature, poly- 

 merization occurs. The characteristic odor and taste of the unsaturated 

 triglycerides may be removed by such treatment. Polymerization is 

 undoubtedly associated with profound changes, not only in the physical 

 properties but also in the chemical structure. On extensive heat treat- 

 ment of oils, an increased viscosity develops; this change in physical 

 property is related to a chemical alteration, as is demonstrated by the 

 fact that the degree of unsaturation, determined from the iodine number, 

 is markedly decreased. 



According to Bradley, 102 the most profound change in unsaturated fats 

 during heating centers around the double bonds. Brocklesby 103 has pic- 

 tured the reaction as involving, first of all, the formation of an unstable 

 4-carbon ring which ruptures and rearranges as shown in (1). 



RCH=CHR' RCH— CHR' RCH 2 CHR' 



R-CH=CHR' ' RCH— CHR' RC=CHR' 



Possible transformation of oils on heat polymerization 103 (1) 



This type of reaction is believed to occur between two unsaturated acid 

 residues which are present on the same glyceride, as well as on different 

 molecules. Lassen el al. 104 are of the opinion that the latter hypothesis 

 is the more probable one. The relation between coefficient of digestibility 

 and percent of polymerization is shown in Figure 2. 



Crampton, Farmer, and Berryhill 105 reported a marked decrease in the 

 weight gains per 1000 Cal. of food ingested, in the case of rats fed oils 

 which had been heated at 275°C. The decreased efficiencies were noted 

 with heated corn, herring, linseed, peanut, rapeseed, and soybean oils. 



102 T. F. Bradley, Ind. Eng. Chem., 29, 440-445 (1937). 



103 H. N. Brocklesby, The Chemistry and Technology of Marine Animal Oils, with 

 Particular Reference to Those of Canada, Fisheries Research Bd., Canada, Bull. No. 59, 

 Sect. 5, Chemical and Physical Properties of Fats and Oils, 107-174 (1941). 



10 < S. Lassen, E. K. Bacon, and H. J. Dunn, Arch. Biochem., 23, 1-7 (1949). 



106 E. W. Crampton, F. A. Farmer, and F. M. Berrvhill, J. Nutrition, 48, 431-440 (1951 ). 



