Abstract
Chromatography of typical California white table wine on Sephadex G-25 indicated about 6% of the total phenol assayed by colorimetry with the Folin-Ciocalteu reagent was large protein-tannin complexes excluded from the gel and about 20% was flavonoid rather strongly absorbed and not eluted with 3% acetic acid. About 20% was caftaric (caffeoyl tartaric) acid and related hydroxycinnamates and other known wine phenols. Evidence is presented that about another 32% is tyrosol plus complexes involving hydroxycinnamates (320 nm absorbance) possibly with nucleic derivatives (260 nm absorbance). The remainder, about 20%, appears to include reaction products between oxidized phenols and sulfhydryl compounds. These substances retain fluorescence and other properties suggesting derivation from caftaric acid and related compounds via the action of polyphenol oxidase. The reaction of nucleic acid derivatives with the Folin-Ciocalteu reagent was investigated. Most of these compounds do not react appreciably, although purines with meta disubstitution of hydroxyl or amine groups did react equivalent to a monophenol (½ gallic acid's reactivity). The total nucleic acid content from previous analyses or by spectral calculation on wines tested here would account for only 10% or less of the apparent total phenol content. The validity of analyses for nonflavonoid phenols is considered strengthened.
- Received July 1978.
- Revision received November 1978.
- Accepted November 1978.
- Published online January 1979
- Copyright 1979 by the American Society for Enology and Viticulture
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