Stability of rice bran oil in terms of oryzanol, tocopherols, tocotrienols and sterols

Abstract

The effect of oryzanol, tocopherols and tocotrienols (tocols) and sterols individually and as combinations of two were analyzed for DPPH radical scavenging activity and antioxidant activity. Oryzanol, tocols and sterols were isolated by using column chromatography and then added at known concentrations in stripped RBO. The results showed that tocol added samples are more stable than with oryzanol and sterol as individual additions. Among them T(1) (sample having 0.04% tocols) is more stable than T(2) (sample having 0.08% tocols). Comparing T(1) and T(2) with control oil, T(1) had a peroxide value almost similar to control oil (T(1), 5.68 mequiv/kg : control oil, 5.52 mequiv/kg) showing the antioxidant activity of tocols even in the absence of other micronutrients. The diene value of both T(1) (4.27) and T(2) (4.03) is lower than control oil (6.14). While analyzing combinations, prevention of oxidation was significantly better for oryzanol and tocols combinations, OT(1) had a peroxide value of 10.57 mequiv/kg, OT(2), 10.42 mequiv/kg when compared to the control sample (52.25 mequiv/kg). Similarly the diene value 5.86 (OT(1)) and 7.1 (OT(2)), the p-anisidine value 53.8 and 63 for OT(1) and OT(2), respectively. The DPPH activity of samples T(2) (0.08% tocols) and OT(2) (sample having 0.8% oryzanol + 0.08% tocols) had a lower IC(50) on the initial day and the IC(50) was lowest for T(1) (0.04% tocols) and OT(1) (sample having 1.6% oryzanol + 0.04% tocols) on the final day.