Extent of Deterioration and Formation of Toxic Substances in Cooking Oil (Coconut Oil) when heated repeatedly above smoke point

  • By Ma. Mercy A. Japitana (completed June 2016)


This study was conducted to determine the stability and Me toxic substances formed when cooking oil (Refined, Bleached and Deodorized-Coconut Oil or RBD-CNO) is subjected to heat treatments. Four treatments were used in the study the untreated (UN), (T1) was heated once, (T2) heated twice with intermittent cooling and (T3), heated thrice with intermittent cooling. There were three replicate, for each treatment. The samples were analyzed for fatty acid profit, free fatty acid value, peroxide value and the amount of PAH present. The mean of the results obtained for all treatments were subjected to one way analysis of variance (ANOVA). The fatty acid profile showed that only the lenoleic acid decreased to quantity constantly up to the third heating, significant at 5% ɑ. Free fatty acid and peroxide values showed an increasing trend, which were significant at 5% ɑ. Out of the 22 PAH analyzed, only 1, 6, 7-trimethylnaphthalene showed an increasing trend, significant at 5% ɑ. To compare treatment means from each other, Duncan’s Multiple Range Test (DMRT) was used. The amount of Ienoleic acid showed a significant difference between UN and T1, UN and T2, UN and T3 but treatments T1, T2 and T3 were not significantly different from each other at 5%level of probability. For both the free fatty acid and peroxide values, UN, T1, T2 and T3 showed a significant difference compared to each other at 5% level of probability.

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