Anthocyanin and colour evolution during maturation of four port wines: effect of pyruvic acid addition

The formation of vitisin A-type compounds has been studied in four maturing fortified red port wines stored for 29 weeks at 15 degreesC. The anthocyanin concentrations were determined by high-pressure liquid chromatography (HPLC), and colour changes were monitored by spectrometric measurements. The losses of anthocyanins followed first-order reactions, and the concurrent formation of polymeric pigments was demonstrated. Vitisin A-type compounds were found to be in low concentration in these four naturally maturing fortified wines. The addition of pyruvic acid to the wines led to the formation of large concentrations of vitisin A derivatives. Up to 23 mg litre(-1) vitisin A derivatives (vitisin A and its acylated forms acetylvitisin A and p-coumarylvitisin A) could be determined. Owing to their greater colour expression and greater stability than malvidin 3-glucoside, these new anthocyanins were shown to play an important role in the colour quality of the wines. An analytical survey of 32 port wines matured for between 2 and 6 years showed that vitisin A-type compounds were the main, and sometimes the only, anthocyanins present. (C) 2000 Society of Chemical Industry.