Studies on the nutritional and physiological effects of thermally oxidized oils

Abstract

SummaryThe present results indicated that the thermal oxidation products from the polyunsaturated fatty acids, primarily linoleic acid, are responsible for much of the loss of nutritional value in thermally oxidized edible oils. Oils which have a high linoleic acid content are more likely to undergo thermal oxidative damage than those with lower linoleic contents. Also the ratio of linoleic acid to total unsaturation has some effect on the nutritive stability of the oil when it has been thermally oxidized. An oil with a high iodine value but with a low linoleic acid value appears to be more stable to thermal oxidation than an oil with an iodine value one half as great but with most of the unsaturation in the oil caused by linoleic acid.The products formed during thermal oxidation which cause the loss of nutritional value are those which do not form urea‐inclusion compounds. They are probably polymeric in nature, but thermally oxidized oils also contain carboxylic acids and carbonyl groups which might cause some of the nutritional loss observed when thermally oxidized oils are fed.The rate ofin vitro hydrolysis of the thermally oxidized corn oil by pancreatic lipase, also the rate of absorption from the intestine of the male rats, were found to be decreased. However the percentage of absorption in 24 hrs. was the same with both fresh and thermally oxidized oil.The liver‐body weight ratio of rats fed a diet containing the thermally oxidized oil were found to be significantly larger than the liver‐body weight ratio in animals fed diets containing fresh oil. However the livers of animals fed the thermally oxidized oil diets did not differ in lipide percentage or total solid content, and histopathological investigations did not show any abnormal conditions.