Review. Recent advances in lipid oxidation

Authors

  • Edwin N Frankel

    1. Department of Food Science & Technology, University of California, Davis, California 95616, and Northern Regional Research Center, Agricultural Research Service, US Department of Agriculture, Peoria, Illinois 61604, USA
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  • This review is based on the 1990 International Lecture addressed to the SCI's Oils and Fats Group in London, 11 April 1990.

Abstract

In a major pathway of the autoxidation of methyl linolenate, peroxyl radicals of the internal hydroperoxides undergo rapid 1,3-tyclisation to form hydroperoxyepidioxides. Because linolenate hydroperoxides are relatively unstable, free radical antioxidants are much less effective in linolenate oils than in linoleate oils. Tocopherols and carotenoids effectively inhibit photosensitised oxidation of vegetable oils. Direct gas chromatographic analyses of malonaldehyde do not correlate with the TBA test. Model fluorescence studies indicate that malonaldehyde may not be so important in crosslinking with DNA. In contrast to oxidised methyl linoleate, oxidised trilinolenin does not form dimers. Although trilinolein oxidises with no preference between the 1(3)-and 2-triglyceride positions, the n-3 double bond of trilinolenin oxidises more in the 1(3)- than in the 2-position. Synthetic triglycerides oxidise in the following decreasing relative rates: LnLnL, LnLLn, LLnL, LLLn (Ln = linolenic and L = linoleic). To estimate the flavour impact of volatile oxidation products their relative threshold values must be considered together with their relative concentration in a given fat.

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