La couleur des vins rouges. lre partie : les équilibres des anthocyanes et des tanins

Abstract

The study covers the equilibria of a mixture of five free anthocyanins from Cabernet Sauvignon skins, depending on the solvent, the tanin content, the pH, and the S02 concentration of the medium. The various constants of the proton transfer, cular extinction of the two coloured forms are determined using the technique of chemical relaxation of these molecules applied to the pH jump ; from these results, the constant of the reaction of the anthocyanins with the S02 on the one hand, and the calculation of the colour of the solutions of these molecules on the other hand, can be determined. From the same study with combinations between tanins and anthocyanins, it is possible to explain the influence of their structure on the stabilization of colour in the solutions. In the light of these results, the chemical origin of the wine colour and its variations are discussed.