Antioxidant Efficacy of Gamma-Oryzanol and Tocotrienol-Rich Fractions from Rice Bran in Chia Seed Oil under Accelerated Oxidation Conditions

Abstract

The antioxidant efficacy of gamma-oryzanol rich fraction (OzF) and tocotrienol rich fraction (TRF) extracted from rice bran in retarding oxidation of chia seed oil (CSO) were evaluated and compared to butylated hydroxy toluene (BHT) during storage at 63 ℃. The total phenolic and flavonoid compounds in CSO and antioxidant activities of OzF and TRF were determined. OzF showed better metal chelating activities compared to TRF, whereas ABTS radical and superoxide anion scavenging activities were comparable for the both. The protective effects of aforesaid extracts in stabilizing CSO were tested by measuring some oxidation indices of oils related to primary and secondary oxidative compounds. Under storage conditions, the oxidative indices were increased faster in untreated oils than those of antioxidant rich fractions incorporated oils which indicate smaller release of oxidative products in later ones. However, the presence of OzF and TRF in CSO decreased the oxidation deterioration of polyunsaturated fatty acid measured by gas-liquid chromatography. In FTIR, the peak intensities in CSO were greatly altered compared to the rest samples during storage. Changes in color value, carotenoids and chlorophyll derivatives contents in CSO were greater than those of the remaining samples during oxidation time. Under the above oxidation conditions and in most cases studied herein, the antioxidant efficacy in stabilizing CSO followed the order: OzF + TRF > BHT > OzF > TRF. This study may open up new opportunities for further technological development in generating stable edible oils, which have potential applications in different types of processed foods.