Structure and properties of wine pigments and tannins.pdf -...

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Am. J. Enol. Vitic. 57:3 (2006)298Phenolic compounds are essential for the quality ofplant-derived food products and wine. They are respon-sible for the color of red grapes and wines and are in-volved in the oxidative browning of white wines. Theyalso contribute to taste and astringency through interac-tions with salivary proteins.Two groups of phenolic compounds are classicallydistinguished: flavonoids based on a common C6-C3-C6skeleton (Figure 1) and nonflavonoids. Each group isfurther divided into several families, with shared struc-tural features that confer specific properties such ascolor, aroma, and taste. Two groups of flavonoids, theanthocyanins and flavanols, are particularly important tothe quality of red wines. Anthocyanins are the red grapepigments. Flavanols exist as catechin monomers and asoligomers and polymers, also called condensed tanninsor proanthocyanidins. Other flavonoids are also presentin low amounts, such as flavonols (for example, querce-tin) and dihydroflavonols (for example, astilbin).Wine phenolic composition depends on the grape usedand on winemaking processes that determine their extrac-tion into the must and subsequent reactions. Anthocya-nins and most tannins are localized in the solid parts ofthe cluster and are extracted by maceration in the ferment-ing must. They are highly unstable and undergo variousenzymatic and chemical reactions as the wine is made andaged. Because the new compounds formed often exhibitsensory properties different from those of their precur-sors, these structural modifications change wine quality.In particular, the color change from the purple tint ofyoung red wines to the tawny nuance of older ones is as-cribed to reactions of grape anthocyanins with tanninsgenerating new polymeric pigments (Somers 1971). Simi-larly, the decrease in astringency as wine ages results frompolymerization of tannins and/or formation of polymericpigments. The occurrence of such reactions in wine andtheir role in sensory changes is generally acknowledged,but the structures of the resulting products have only re-cently been established through new analytical tech-niques, and studies on their sensory properties have juststarted. Although color and taste depend primarily on mo-lecular structure, they are modulated by interactions be-tween each other and with other compounds present in thewine and in saliva. This review summarizes current knowl-edge on the structure of grape and wine pigments andtannins and on their role in determination of wine quality.Structure of Anthocyanins and TanninsSimple phenolic compounds and their distributionwithin the grape berry are well documented. Anthocyanins(Figure 1) are specific to red varieties and localized inStructure and Properties of Wine Pigments and TanninsVéronique Cheynier,1* Montserrat Dueñas-Paton,2Erika Salas,3ChantalMaury,4Jean-Marc Souquet,1Pascale Sarni-Manchado,1and Hélène Fulcrand11INRA, UMR Sciences pour l’OEnologie, 34060 Montpellier cedex, France;2Postdoctoral researcher, INRA;3

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Term
Fall
Professor
Colin Leasure
Tags
Oenology, Am J Enol, V Cheynier

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