Anthocyanin profile in berry skins and fermenting must/wine, as affected by grape ripeness level of Vitis vinifera cv. Shiraz/R99.

摘要

The release of anthocyanin compounds from berry skins into the wine is affected by several viticulture and oenological practices. Ripeness level seems to play a significant role. The study aimed to evaluate the extraction kinetics of individual anthocyanins from grape skins into wine under controlled conditions of small-scale vinification of Shiraz grapes, harvested at three ripeness levels (23, 25 and 28 degrees Brix). The anthocyanin profile of intact berry skins, fermenting musts/wines and crushed skins during the period between crushing and pressing was analysed by HPLC. Ripeness level greatly impacted on the skin / juice ratio (ranging from 169 +or- 4.5 g L--1 at 23 degrees B, 185 +or- 7.2 g L--1 at 25 degrees B and 256 +or- 10.7 g L--1 at 28 degrees B) and on grape anthocyanin concentration (ranging from 0.80 +or- 0.13 g kg--1 at 23 degrees B, 0.78 +or- 0.07 g kg--1 at 25 degrees B and 1.21 +or- 0.13 g kg--1 at 28 degrees B) and profile (%) at harvest. In addition, it affected the rate and amount of individual anthocyanin extraction from skins into wine and their transformation during fermentation, consistent with the relevant chemical group classification (3-glucoside, 3-acetyl-glucoside, 3-p-coumaroyl-glucoside). At pressing, the anthocyanin concentration of the three wines was similar (319 mg L--1, on average), but the anthocyanin profile was different, particularly the ratio of 3-glucoside / 3-p-coumaroyl-glucoside derivatives, which was on average 3.55 at 23 degrees B and 25 degrees B and 2.6 at 28 degrees B. Viticultural choices, such as to harvest earlier or later, influencing the chemical and physical composition of the berries, may influence the extraction kinetics of individual anthocyanins and their destiny in the fermenting must, offering to winemakers different basic wines suitable for the production of different wine products. These findings are valuable to improve viticultural and oenological practices for Shiraz wine production, allowing the improvement of wine quality and the purposeful creation of different styles of wine