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Antioxidative effect of ethanol tea extracts on oxidation of canola oil
Author(s) -
Chen Z. Y.,
Chan P. T.,
Ma H. M.,
Fung K. P.,
Wang J.
Publication year - 1996
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/bf02523434
Subject(s) - canola , chemistry , food science , butylated hydroxytoluene , polyphenol , antioxidant , lipid oxidation , ethanol , fermentation , biochemistry
There is an increasing interest in the biological effects of natural antioxidants present in teas on formation of in vivo free radicals, carcinogenesis, and atherogenesis. Teas are traditionally classified into six major groups, namely, green, yellow, white, black, dark‐green, and oolong teas. The present study examined the antioxidative activity of ethanol extracts from these six major groups of teas against oxidation of heated canola oil. The oxidation was conducted at 100°C by monitoring oxygen consumption and changes in linoleic and linolenic acids in canola oil. The ethanol extracts of green, yellow, and white teas strongly inhibited oxidation of canola oil compared to butylated hydroxytoluene, probably due to the presence of natural polyphenols. In contrast, oolong teas examined exhibited only moderate antioxidative activity because of the partial destruction of natural polyphenols by semifermentation. The ethanol extracts of black, dark‐green, and ginseng teas studied showed little or no protection to canola oil from lipid oxidation, probably due to the complete destruction of natural polyphenols by fermentation during manufacturing processes.