Physico chemical,nutritional and toxicological evaluation of thermally oxidised edible oils

Abstract

“Physico chemical, nutritional and toxicological evaluation of thermally oxidized edible oils” were determined by assessing their changes in physical and chemical properties, nutritional changes ie changes in fatty acid composition and toxic as well as mutagenic effect in relation to reheated oils taking fresh oils as check. Among the five factors considered for physic chemical analysis in both the coconut and ground nut oil the boiling point were found to be decreasing consequent to reheating. In case of smoke point a reverse trend was observed. Acid value of coconut oil were found to be decreasing consequent to reheating but it was vice versa in case of groundnut oil. Iodine values of both the oils were observed to be decreasing from the fresh to 12 hours reheated sample. Coconut oil showed a regular increase in saponification value where as in groundnut oil it is found to be decreasing. Nutritional changes were observed by observing changes in fatty acid composition of fresh as well as reheated oils with 2hours interval. The data observed ended in conclusion that as the time of heating increases there will be increase in content of short and medium chain fatty acid and a decrease in content of short and medium chin fatty acid and a decrease in content of unsaturated fatty acids contribute only 5 percent of total fatty acid. From the nutritional point of view essential fatty acids were decreased to a minimum in case of groundnut oil with increase in saturated fatty acid. A preliminary feeding of 6 months duration was conducted with two control groups fed with fresh coconut oil and groundnut oil at 9 percent level and experimental group with reheated coconut oil in the same level for toxicological evaluation. The results of study revealed that gain in body weight were significantly higher for controls when compared with experimental groups. The animal feeding experiment was undertaken also to estimate the effect of reheated edible oils with regard to histopathological changes in animals. Histopathological investigations was carried out by taking major organs viz, liver, kidney and intestine at two periods during the course of experiment. Liver was the organ that showed changes other than congestion. Hepatocytes showed microvesicular fatty changes of varying degree in both control and experimental groups. The central veins and sinusoids showed only congestion where as kupffer cells did not show much alteration in all cases. Kidney appeared normal in all cases with exception of few hyaline casts in the lumen. Intestine appeared normal in all cases. Toxicological evaluation of fresh and 12 hours reheated coconut oil also was evaluated by mutagenicity screening in bacterial system salmonella typhimurium TA 1535 strains without activation. The study resulted in conclusion that the colonies developed as a result of induction of experimental carcinogen ie reheated oil were very few when compared with positive control. So that the chance of being possible carcinogen can be eliminated. Thus in conclusion reheated oils upto 12hrs are not much harmful to health, though they may produce changes in the physic chemical properties as well as nutritional aspects. Short term consumption of these oils also bring about slight alteration in the internal tissues. Mutagenic and toxicological studies are to be conducted for longer periods with thermally oxidized edible oils to get final results. So it seems difficult to draw decisive conclusion from this study to prove that highly thermally abused oils are detrimental to health.