Stability of Rice Bran Oil in Terms of Oryzanol, Tocopherols, Tocotrienols and Sterols

摘要

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 T1 (sample having 0.04% tocols) is more stable than T2 (sample having 0.08% tocols). Comparing T1 and T2 with control oil, T1 had a peroxide value almost similar to control oil (T1, 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 T1 (4.27) and T2 (4.03) is lower than control oil (6.14). While analyzing combinations, prevention of oxidation was significantly better for oryzanol and tocols combinations, OT1 had a peroxide value of 10.57 mequiv/kg, OT2, 10.42 mequiv/kg when compared to the control sample (52.25 mequiv/kg). Similarly the diene value 5.86 (OT1) and 7.1 (OT2), the p-anisidine value 53.8 and 63 for OT1 and OT2, respectively. The DPPH activity of samples T2 (0.08% tocols) and OT2 (sample having 0.8% oryzanol + 0.08% tocols) had a lower IC50 on the initial day and the IC50 was lowest for T1 (0.04% tocols) and OT1 (sample having 1.6% oryzanol + 0.04% tocols) on the final day.