Nutritive value of methyl linoleate and its thermal decomposition products

Abstract

Methyl linoleate was heated for 10 hrs. at 300~ in the absence of air and fractionated by alembic distillation and urea adduct-formation.Intestinal absorptions of the urea adduct-fornling monomeric nonadduct-forming nlonomeric, and dimeric fractions were determined. It was found that dimers were half as well absorbed as the monomers.When fed to rats, dimers were better accepted and exhibited some toxicity symptoms different from the nonadduct-fornling monomers. The dinlers caused diarrhea, irritability, and loss of hair during the early period of administration. The nonadduct-forming monomers were lethal and produced an increase in liver weight. Both fractions depressed growth. HEATING Of unsaturated oils in the absence of air is known to result in the formation of a mixture of monomeric and polymeric substances, both linear and cyclic. For reviews on the nutritional significance of such compounds the reader is referred to the papers of Brown (1) and of Rice et al. (2).Crampton and co-workers (3,9) have been able to demonstrate that, when linseed, soybean, and sunflower oils are heated at approximately 275~ for 12 to 26 hrs. in a C02 atmosphere, a polymeric fraction, which is very slightly absorbed from the intestine of the rat, and a nonurea adduct-forming monomerie fraction, which is harmful to the same animal, are formed. Comparison of the fatty acid composition of these oils with their deleterious action indicates that linolenic acid is the main precursor. Nevertheless some toxicity has been found to develop in heated oils containing relatively high proportions of linoleic add and no linolenie acid.More unsaturated oils, such as fish oils, seem able to develop toxic effects and form poorly absorbed substances if heated and administered under similar conditions (10-15).Methyl and ethyl linoleate seem also capable of forming cyclic and polymeric substances by heating, as has been suggested by Paschke et al. (16,17).In order better to characterize the toxic derivatives and their biological properties, relatively pure methyl linoleate was prepared, heated in the absence of air, then fractionated. The fractions were tested for intestinal absorption and deleterious action in the rat.Recently Kaunitz et al. (18) have made a similar study on thermal oxidation products of the same ester.

Nutrition and metabolic studies of methyl esters of dimeric fatty acids in the rat

“…Crampton et al (7,15), Kaunitz et al (8), and Perkins et al (9) showed that diets containing 12-20% dimers caused high mortality rates when fed to the rats. At 5-10% of the diet, dimers decreased growth rate and lowered food efficiencies (8,10,11). The high mortality of rats fed 12-20% dimers may have been caused mainly by malabsorption rather than the toxicity of the dimers.…”

“…Nutritional studies (7)(8)(9)(10)(11)(12) conducted on the dimer and polymer fractions of heated fats showed in some cases that rats fed high levels of dimer concentrates or polymers exhibited adverse effects such as depressed growth, diarrhea, oily and matted coats, lower basal metabolism, lower body temperature, and higher mortality rate. Although the apparent digestibility of dimers had been shown to be between 30 and 70% (10,13,14), their absorption by the rat has been questioned (15)(16)(17). In the present study, nonlabeled and 14Cqabeled methyl esters of dimeric fatty acids were prepared, and the absorption and nutritional effects of these dimers in the rat were investigated.…”

Short‐term in vivo digestibility assessment of a highly oxidized and polymerized sunflower oil

“…11,12 However, data concerning triacylglycerol oligomer digestibility are confusing. 14,15 Our group has found that true digestibility of the different thermoxidized compounds from the heated olive oil was 30-40%, whereas that of thermoxidized compounds from the unused oil was much higher (80%). 16 Moreover, the digestibility of nonoxidized triacylglycerols seems negatively affected by the presence of large amounts of thermoxidized compounds in palm olein and olive oil.…”

Column and high‐performance size exclusion chromatography applications to the in vivo digestibility study of a thermoxidized and polymerized olive oil

“…Moreover, it appears that triacylglycerol monohydroperoxides are hydrolyzed by pancreatic lipase to almost the same degree as the original triacylglycerols (11,12). However, data concerning triacylglycerol oligomer digestibility are confusing (14,15).Studies on altered fat digestibility often use radiolabeled markers, which do not always have the same composition as the altered compounds present in heated or used frying fats. Moreover, these markers are potentially harmful and rather expensive.…”

“…Moreover, it appears that triacylglycerol monohydroperoxides are hydrolyzed by pancreatic lipase to almost the same degree as the original triacylglycerols (11,12). However, data concerning triacylglycerol oligomer digestibility are confusing (14,15).…”