Model wine solutions: Effect of sulphur dioxide on colour and composition during ageing

The effect of sulphur dioxide and acetaldehyde on the interaction between malvidin 3-glucoside, the main anthocyanin in red wine made from Vitis vinifera grapes, and (+)-catechin was examined. In all model wines the molar losses of malvidin 3-glucoside were significantly greater than the losses of catechin. The concentration of malvidin 3-glucoside decreased fastest in the presence of acetaldehyde while the most rapid loss of catechin occurred in the model containing malvidin 3-glucoside and catechin only. In the presence of sulphur dioxide, these losses still occurred, but much more slowly, indicating that condensation reactions may take place even in the presence of sulphur dioxide. Polymerisation was most prominent in the model containing malvidin 3-glucoside, catechin and acetaldehyde. Concurrent with the losses in anthocyanin and catechin, qualitative and quantitative changes in visible colour were also observed. Changes in colour monitored by measuring hue angle and chroma are also reported