The inhibition of cholesterol autoxidation by nonsaponifiable fraction from rice bran oil (700, 1400, and 2100 ppm) was studied in an aqueous model system for 16 h at pH 5.5 and 80°C. Antioxidant effectiveness was investigated by following the loss of cholesterol and the formation of 7-ketocholesterol. The changes in levels of vitamin E vitamers and γ-oryzanol in the system were determined during cholesterol autoxidation. The 2100 ppm treatment produced a 92% reduction of 7-ketocholesterol, 1400 ppm an 82% reductions and 700 ppm a 64% reduction after 16 h, whereas without the nonsaponifiable fraction, the samples showed almost complete degradation of cholesterol. Vitamin E vitamers decreased (P < 0.05) in all treatments, but γ-oryzanol was not significantly (P > 0.05) reduced in the 2100 ppm treatment.Paper no. J9675 in JAOCS 78, 685-689 (July 2001).

Crude rice bran oil 0, 1 %, and 2% (w/w), was added to restructured beefroasts that were stored at 4C and analyzed at 0, 7, and 14 days to determine nutritional properties and oxidative stability. The saturated f a t y acid to unsaturated fatty acid (SFMUFA) ratio and the content of 7-ketocholesterol decreased (j60.05) whereas vitamin E vitamers increased ($0.05) in the product with 2% rice bran oil. TBARs numbers were lower (pCO.05) in roasts with rice bran oil afer 7 days of storage. The addition of 2% rice bran oil (w/w) was effective in improving both oxidative stability and vitamin E levels.

: The antioxidant activities of E vitamer fraction extracted from rice bran were investigated and compared with α‐tocopherol at 2 concentration levels (16 ppm and 160 ppm) in the emulsified cholesterol and linoleic acid systems. 7‐Ketocholesterol, 7α‐hydroxycholesterol (7α‐OH), 7β‐hydroxycholesterol (7β‐OH), 25‐hydroxycholesterol (25‐OH), and 5,6‐epoxycholesterol (5,6‐EP) were found at different incubation times (0, 6, 12, 24, and 48 h) in the emulsified cholesterol system accelerated by using 2, 2′‐azobis (2‐methylpropionamidine) dihydrochloride (AAPH) at 80°C and pH 5.5. Samples treated with 160 ppm of E vitamer fraction exhibited a significant antioxidant activity by inhibiting the formation of cholesterol oxidation products (COPs). Addition of E vitamer fraction to the emulsified linoleic acid model at 37°C significantly inhibited the hydroperoxide formation and decomposition more than that of α‐tocopherol. The former was more effective in inhibiting the primary and secondary oxidations of the polyunsaturated fatty acid (PUFA). No significant differences (P < 0.05) were found in inhibition of the linoleic acid autoxidation between the E vitamer fraction and the α‐tocopherol at 16 and 160 ppm, respectively. E Vitamer fraction was most effective in inhibiting both emulsified cholesterol and linoleic acid. These results suggested that compounds inhibiting cholesterol autoxidation and PUFA autoxidation in both food and biological systems were present in the rice bran extract. Thus, the addition of E vitamer fraction to animal‐ derived muscle food may be a more compelling way to replace the synthetic antioxidants currently used in the food industry because the former is both natural and effective in inhibiting both cholesterol and PUFA autoxidation.