Effects of Vineyard and Winemaking Practices Impacting Berry Size on Evolution of Phenolics during Winemaking

摘要

Four methods of regulated deficit irrigation (RDI), an irrigation technique whereby water is supplied at rates at or below the full evapotranspiration (ET_c), were applied to Cabernet Sauvignon grapes. The grapes were thereafter processed with three winemaking techniques: control (10-day maceration), extended maceration (EM; 30-day maceration), and saignee (removal of 16% of must by volume at crushing). The 25% ET_c treatment had higher concentrations (fresh weight basis) of skin anthocyanins and seed tannins. Overall, skin tannins showed increased biosynthesis in 100% ET_c and 25/100% ET_c, whereas seed tannins were mostly (positively) affected due to a reduction of fresh weight in 25% ET_c. Extraction of anthocyanins and tannins during winemaking ranged from 40 to 73% and from 17 to 26%, respectively. During maceration, the extraction curves for both anthocyanins and tannins were unaffected by the RDI treatments; quantitative differences were caused primarily by the winemaking treatments and secondarily by the RDI treatments. Consistent with a higher content of anthocyanins, 25% ET_c wines had higher concentrations of polymeric pigments and greater color saturation and a~* (red color component) both at day 30 and after 120 days post-crushing. EM enhanced seed tannin extraction, which resulted in a 50% increase in wine tannins relative to control and saignee wines, but it lowered anthocyanins and color saturation. Saignee increased anthocyanins at day 5 by 22% and tannins by 24% (relative to control wines), resulting in higher concentrations of polymeric pigments after 120 days. Both saignee and control wines had a roughly equivalent proportion of seed- and skin-derived tannins, whereas EM wines had 73% seed-derived tannins.