Effect of sulphur dioxide and must extraction on colour, phenolic composition and sensory quality of red table wine

Abstract

Red wines were made during 1992 from Vitis vinifera var Roriz grapes using a high and a low level of extraction and three levels of total sulphur dioxide (0, 75 and 150 mg SO2 kg−1). From this single experiment, the effects of total SO2 and extraction on anthocyanin composition and colour were observed by HPLC, spectrophotometry and tristimulus colorimetry. High extraction produced a wine with more total pigments and total phenols than low extraction and increased the amount of organic acids extracted during fermentation. More anthocyanins were extracted with increasing SO2 levels. On maturation, all wines lost colour and increased in brownness. Wines made without SO2 browned more than the wines made with SO2. The anthocyanins normally present in wines were all rapidly lost to trace levels at 24 months. Vitisin A, a more stable and highly coloured anthocyanin than malvidin 3-glucoside, showed a slower decrease in concentration than malvidin 3-glucoside and contributed significantly to the wine colour during aging. At the first analysis, the wines made without SO2 had a higher percentage colour due to polymers than the wines made with SO2. Polymerisation progressed during maturation, although the initial differences were maintained. Sensory analysis after 6 and 18 months storage by expert tasters revealed differences mainly related to the colour attributes, indicating that when wines are made using modern hygienic techniques, total SO2 has a negligible effect on aroma and flavour attributes. © 1998 Society of Chemical Industry.