Oryzanol as natural antioxidant for improving sunflower oil stability

Sunflower oil is being made shelf stable by the incorporation of synthetic antioxidants such as tertiary butyl hydroquinone (TBHQ), while natural antioxidants like oryzanol and tocopherols can also be used. The aim of the current investigation was to evaluate the antioxidant effect of natural oryzanol (Oz) concentrate (15.5 % oryzanol) and purified Oz (80 % oryzanol) on oxidative and thermal stability of sunflower oil. Sunflower oil was incorporated with Oz concentrate to provide 0, 0.12, 0.25, 0.50, 0.84, 1.0, 1.60, 2.0, 2.5 and 3.20 % oryzanol in the oil, stored for 5 weeks at 37 °C and oxidative stability was evaluated. It was found that the oryzanol concentrate showed good antioxidant effect with increase in concentration of oryzanol. In another set of experiments, sunflower oil containing purified Oz at 1 % level individually and in combination with 0.1 % α- tocopherol (α-T) was heated at 120 °C for 24 h to evaluate thermal stability. Sunflower oil containing 1 % Oz (80 % purity) showed 98.40 % and sunflower oil containing 1 % Oz and 0.1 % α-T showed 108.75 % antioxidant effect compared to TBHQ taken as 100 %. The study indicated that sunflower oil containing 1 % Oz (80 % purity) and 0.1 % α-T combination provides a synergistic effect in inhibiting primary and secondary products and showed highest thermal stability. SFO containing 1 % Oz added as concentrate also showed good antioxidant effect during storage. Hence, instead of using synthetic antioxidants like TBHQ, we can add natural oryzanol (purified or as concentrate) to sunflower oil to increase its oxidative and thermal stability.