Effects of seed tannins on enzymatic decolorization of wine pigments in the presence of oxidizable phenols

Red pigments were isolated from skins of Cabernet Sauvignon grapes and flavonoid phenols were isolated from their seeds. Red table wine was produced from the same lot of grapes. Three red pigment fractions-monomeric anthocyanins, oligomeric pigments, and polymeric pigments-were fractionated by successive extraction with isoamyl alcohol and 1-butanol. The extraction of anthocyanins with isoamyl alcohol was significantly inhibited by SO2 present in the wine, but the interference by SO2 was removed by the addition of acetaldehyde. Seed phenols were fractionated into four fractions-catechins, dimeric phenols, oligomeric tannins, and polymeric tannins-by partition chromatography. Insoluble polyphenoloxidase (PPO) isolated from the must precipitate did not oxidize the seed dimeric phenols or polymeric tannins, but decolorized the whole pigment and three wine pigment fractions in the presence of diphenols. The seed dimeric phenols and polymeric tannins somewhat suppressed decolorization of the whole pigment but did not influence decolorization of wine fractions.