Influence of ascorbic acid, sulfur dioxide and glutathione on oxidation product formation in wine-like systems

Abstract

The impact of the addition of ascorbic acid, sulfur dioxide and glutathione on oxidation product formation under accelerated oxidative conditions was evaluated in model wines. The effects of these antioxidants have been compared in aqueous ethanol solutions containing (+)-catechin and metal ions at pH 3.2 by monitoring O2 consumption, color evolution by CIELab, as well as (+)-catechin and glutathione decrease by LC-DAD/FD. The analysis of oxidation products formation was focused on the determination of yellowish colored xanthylium compounds by LC-ESI-ToFMS and acetaldehyde by HS-GC-FID. The results could show, that under some conditions glutathione could not inhibit carboxymethine-briged (+)-catechine dimer formation and subsequent xanthylium cation pigment generation, compared to ascorbic acid or sulfur dioxide addition providing a good protec- tion against oxidative color changes. In systems containing 0.08–0.32 mmol/L glutathion without any further addition of SO 2 or ascorbic acid, increasing acetaldehyde concentrations could be observed. These results demonstrate clearly the need for further research to highlight the reactions of glutathione.