Effect of endogenous antioxidants of sesame seeds and sesame oil to the thermal stability of edible vegetable oils

Differently processed sesame seeds were used for the preparation of sesamol, seed extract, oil extract or unsaponifiable matter. Analysis of these sesame extracts revealed that dehulling and roasting of seeds had an adverse effect on their lignan and phenolic compounds content. Various concentrations of the extracts were incorporated in vegetable oils and their effectiveness in retarding the oxidative deterioration of oils was evaluated. Additionally, the formation of oxidation products in these oil samples was correlated with their antioxidant activity and their sesamol and phenolic compounds content. Results indicated that decomposition of phenolic compounds present in oil samples induced a significant reduction in their linoleic acid peroxidation inhibition capacity and a corresponding increase in their oxidative rancidity. Sesame seed extract was the most effective in protecting oils from oxidation, suggesting that seed extract, especially the one prepared from coated-unroasted sesame seeds, may have potential application as a source of natural antioxidants in oil industry.