46C-26 |
Antioxidant activity of g-oryzanol and synthetic phenolic compounds |
J. S. KIM1, K. N. Kim1, and H. Y. Chung2. (1) Pulmuone R&D Center, Pulmuone Co., Ltd., Seodaemun PO Box 146, Seodeamun-Ku, Seoul, 120-600, South Korea, (2) Dept. of Biology, Chinese Univ. of Hong Kong, Food Sci. Lab., Shatin, N.T., Hong Kong SAR, HKG, China Autoxidation of polyunsaturated fatty acids (PUFA) is believed to play an important role in atherosclerosis, cancer, and aging process. The defense mechanism against PUFA autoxidaion in cellular membranes is thought to involve chain-breaking antioxidants. Oil/water emulsion system is often used to simulate the conditions in cellular membrane. Phenolic compounds are well-known chain-breaking antioxidants. However, antioxidants are difficult to be evaluated in emulsions due to their different interfacial affinity in oil/water system. g-Oryzanol is one of the chain-breaking antioxidants. Both sterol (triterpene) and phenolic hydroxyl group in the structure of g-oryzanol may be responsible for its antioxidantive function. We hypothesize that g-oryzanol is more effective in preventing autoxidation of PUFA than the synthetic phenolic compounds in oil/water system. The purpose of this research was to investigate the antioxidant activity of g-oryzanol and synthetic phenolic compounds in oil/water emulsions at 80 C. Ten percent soybean oil/water emulsions were prepared with oils containing antioxidants (0, 25, 50, 100, and 200ppm of g-oryzanol or 200ppm each of TBA, TBHQ, BHA), Tween 20, and sepigel. The effectiveness of antioxidants was evaluated at different oxidation stages (0, 4, 8, 16, and 32h) by measuring both the formation of conjugated diene hydroperoxides and the decomposition of hydroperoxides (hexanal) in each emulsion. The initial rate of hydroperoxide formation in the control increased sharply after an induction period of 16h. Overall, the order of effectiveness of various antioxidants for inhibiting the formation of hydroperoxide in the emulsion was: g-oryzanol>TBHQ>BHT>BHA. Emulsion with lower concentrations of g-oryzanol showed better effectiveness than that with high concentration of synthetic antioxidants. However, the ability of both g-oryzanol and synthetic antioxidants to decompose hydroperoxide was similar. This study showed the effectiveness of g-oryzanol than synthetic antioxidants to inhibit the formation of hydroperoxide in oil/water emulsions.
Session 46C, Food Chemistry: Lipids, antioxidants and emulsifiers
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