Grape phenolics are structurally diverse, from simple molecules to oligomers and polymers that are usually designated “tannins,” referring to their ability to interact with proteins. Anthocyanin pigments and tannins are particularly important for red wine quality. Their extraction depends on their location in the berry and their solubility. All phenolic compounds are unstable and undergo numerous enzymatic and chemical reactions. Color and taste changes during red wine aging have been ascribed to anthocyanin-tannin reactions. The structures and properties of tannins and pigmented tannins from these reactions are often misunderstood. Current research on wine phenolic composition is reviewed, with emphasis on the following issues: (1) reactions of tannins yield both larger polymers and smaller species; (2) anthocyanin reactions can generate colorless species as well as polymeric and small various pigments; (3) some polymeric pigments undergo sulfite bleaching while some low molecular weight pigments do not; (4) polymers are both soluble and astringent, so the astringency loss during aging may involve cleavage rather than polymerization; and (5) sensory properties of anthocyanins and tannins are modulated by interactions with other wine components.
Acknowledgments: Part of this research has been funded by Société Martin Vialatte, by grants from Consejo Nacional de Ciencia y Technologia (Mexico), Société Francçaise d’Exportation des Ressources Educatives (France), and Ministerio de Educacion, Cultura y Deporte (Spain).
This article was originally presented at the ASEV 56th Annual Meeting Phenolics Symposium, 20–21 June 2005, Seattle, WA. All phenolics symposium articles were peer reviewed by two fellow presenters, and James Harbertson, Mark Downey, and Sara Spayd served as technical editors of the articles.
From the ASEV 2005 Phenolics Symposium
- Copyright © 2006 by the American Society for Enology and Viticulture