46C-24 |
Effect of gallic acid on thermal oxidation of vegetable oils during heating at 180”ĘC |
T. S. Hahm, Food & Biotechnology, Hanseo University, 360, Daegok-ri, Haemi-myun, Seosan, 356-706, South Korea and M. Y. JUNG, Food Science & Technology, Woosuk University, 490 Hoojeong-Ri, Samrea-Up, Wanju, 565-701, South Korea. A large portion of fats and oils is used for the preparation of fried foods. Oils undergo a complex series of changes and reactions during frying. The chemical changes during frying are due to the thermal oxidation of oils at the elevated temperature around 180oC. The commonly used antioxidants (BHA and BHT) reportedly do not have antioxidative effect at high temperature. The objective of this research was to study the effect of gallic acid on the thermal oxidation of vegetable oils by measuring the changes in fatty acid composition, and conjugated diene and polymer formation during heating at 180oC for 8 days. Gallic acid treatment significantly reduced the changes in fatty acid composition, and conjugated diene and polymer formations in vegetable oils during heating, and its effectiveness was concentration dependent. The ratio of linoleic acid to palmitic acid (C18:2/C16:0) was changed from 2.43 to 1.38 after 8 days heating. The ratios of C18:2/C16:0 of cottonseed oil treated with 0.02%, 0.05% and 0.1% gallic acid were 1.44, 1.57 and 1.81 after 8 day heating, respectively. The 0.1% gallic acid treatment showed 17% inhibition of conjugated diene formation during 8 day heating. The 0.05 and 0.1% gallic acid treatments inhibited 40.1 and 52.4% polymer (tetramer) formation after 8 day heating, respectively. The treatment of 0.05% gallic acid was significantly more effective for the prevention of fatty acid composition changes, and conjugated diene and polymer formation than 0.02% BHA or 0.02% TBHQ treatments. These results showed, for the fist time, that the gallic acid could be used as an effective antioxidant on the thermal oxidation of vegetable oils at 180oC.
Session 46C, Food Chemistry: Lipids, antioxidants and emulsifiers
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