Copigmentation in Model Wine Solutions: Occurrence and Relation to Wine Aging

Abstract

Copigmentation has been studied in a model wine solution involving malvidin-3-glucoside as the red pigment (the most common anthocyanin in Vitis vinifera) and (-)-epicatechin as the copigment (the most common flavanol monomer present in red wine). Such an interaction has been studied by visible absorption spectroscopy and characterized by the theoretical framework established by Brouillard et al. in 1989. A complex of the 1:1 type has been identified. Moreover this model solution has been kept in the dark at room temperature for ten weeks. New pigments have been partially identified from the reaction, some of them being of the xanthylium type (degradation products). We also have found a red-purple pigment already described in the literature, resulting from acetaldehyde (arising from the ethanol oxidation) bridging malvidin-3-glucoside and (-)-epicatechin. Thus, copigmentation has been found to occur in a model wine and has lend to new pigments, typical of those involved in the wine aging process. Such observations shed light on the possible reactions happening during the aging of red wines.