The production of yellow pigments from (+)-catechin and dihydroxyfumaric acid in a model wine system

The oxidation of tartaric acid by hydroxyl radicals, produced by gamma-irradiation of aqueous solutions of tartaric acid, was shown to generate dihydroxyfumaric acid. To confirm the importance of this oxidative degradation pathway in wine oxidation, dihydroxyfumaric acid was itself reacted with (+)-catechin in a wine-like solution and the yellow pigments formed were identified by liquid chromatography mass spectrometry (LC-MS) studies as xanthylium cations. The concentration of these pigments increased if the wine-like system also contained 0.6 mg/L copper(II). The results clearly demonstrate a link between the production of yellow xanthylium cation pigments from (+)-catechin and the degradation of tartaric acid by hydroxyl radicals.