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Title: ODOR AND OXIDATIVE STABILITY OF STRIPPED SOYBEAN OILS WITH LOW OR HIGH LEVELS OF ALPHA, GAMMA OR DELTA TOCOPHEROLS

Author
item Warner, Kathleen

Submitted to: Annual Meeting of the Institute of Food Technologists
Publication Type: Abstract Only
Publication Acceptance Date: 11/6/2002
Publication Date: 11/16/2002
Citation: WARNER, K.A. ODOR AND OXIDATIVE STABILITY OF STRIPPED SOYBEAN OILS WITH LOW OR HIGH LEVELS OF ALPHA, GAMMA OR DELTA TOCOPHEROLS. ANNUAL MEETING OF THE INSTITUTE OF FOOD TECHNOLOGISTS. 2002.

Interpretive Summary:

Technical Abstract: Research on factors influencing oil quality has shown that fatty acid composition is not the only determinant of quality. Soybean oil is more oxidatively stable than sunflower oil even though soy contains 8% unstable linolenic acid whereas sunflower has none. Oil antioxidants such as tocopherols inhibit oxidation; however, effects of different ratios of tocopherols on oil quality is unknown. Our objective was to determine inhibition of oxidation of purified vegetable oils with various ratios and amounts of added pure tocopherols. Soybean oil was stripped of minor constituent to prepare 8 samples with low(L) or high(H) levels of alpha (100 or 500ppm), gamma (50 or 400ppm), or delta (20 or 200ppm) tocopherol (LLL, LHL, LHH, LLH, HHH, HLH, HHL, HLL; listed in order alpha, gamma, delta). Oils were stored at 60 deg.C for 0, 4, and 8 days in the dark. Oxidative stability was measured by peroxide value and volatile compounds. A method was developed to evaluate odors of small oil samples. A trained, experienced analytical panel was given covered 250ml wide-mouth glass jars containing 0.15g oil absorbed on filter paper and rated intensities of odors. Analyses of hexanal and rancid odor intensity showed that the most stable oils had high gamma levels. Samples containing low gamma had significantly higher hexanal and stronger rancid odor. Four oils had tocopherol levels existing naturally: corn(LHL), sunflower(HLL), soybean(LHH), canola(HHL). Oils with tocopherol ratios similar to soybean(LHH) and corn(LHL) had significantly better oxidative and odor stability that did oil containing ratio typical of sunflower(HLL). Results indicate that gamma tocopherol is an important inhibitor of oil oxidation. Soybean and corn oils have increased oxidative stability due in part to high gamma tocopherol concentrations. As plant geneticists develop expertise to modify tocopherols, the impact of high gamma tocopherol needs consideration.