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The phenolic substances contents of 45 plant foods in Korean diet were determined by different methods. Total phenolics contents by Folin-Denis method were 0.1∼5.8% (dry matter basis), in which persimmon leaf, chestnut´s inner skin, Chinese quince, walnut, sunflower seed and arrowroot exhibited the higher levels above 2%. Condensed tannin contents by vanillin method were 0∼48%, in which Chinese quince and chestnut´s inner layer gave very high levels. Protein-precipitable phenolic substances ranged from 0.4% to 2.2, in which chestnut´s inner layer, walnut and Chinese quince had the highest content. The ability of henolics to form precipitate was higher with pepsin and albumin than with trypsin. Among different phenolics content, total phenlolics correlated significantly with protein-precipitable phenolics (r=0.65) and condensed tannin (r=0.56). Chinese quince, chestnut´s inner skin and sorghum showed a relatively lower degree of polymerization, as expressed by vanillin/FolinDenis ratio. Processed foods from buckwheat, acorn, mugwort and arrowroot showed a lower content of phenolic substances, suggesting a negligible adverse effect on the bioavailability of food proteins, if any.
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