Phenolic management in red wines: Investigation of the timing and severity of Regulated Deficit Irrigation (RDI), grape maturity, and selected maceration conditions by HPLC-DAD-MS and sensory techniques
Casassa, Luis Federico
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The extraction into wine of selected phenolics as affected by season, regulated deficit irrigation (RDI), fruit maturity, and selected maceration conditions was studied. Pomace recovery, color, and sensory aspects were also investigated. In addition to a control treatment (10 days of skin contact), the maceration techniques studied included extended maceration (EM, 30 days of skin contact) and bleed-off (i.e. saignée) applied to reduce must volume by 16%. The influence of fruit maturity and ethanol were studied by producing wines from fruit with different sugar levels, and by artificially manipulating sugar levels before fermentation to generate different ethanol levels during maceration. Preparative HPLC fractionation of wine proanthocyanidins (PA) followed by HPLC-DAD-MS analysis was undertaken to determine PA distribution. Sensory properties were studied using Quantitative Flavor Profiling and Descriptive Analysis. Wines made from ripe fruit (ca. 24.5 Brix) extracted 16% of the available tannins (of which 79% were seed-derived tannins) whereas in unripe fruit (ca. 20 Brix) this extraction was 12% (76% of seed-derived tannins). Ethanol differences as high as 2.7% v/v during maceration had no effect on tannin and anthocyanin extraction, or in the proportion of seed- and skin-derived tannins. Wines obtained from ripe fruit were characterized by attributes such as viscous mouthfeel, sweetness and fruit-derived aromas. Wines made from unripe fruit were characterized by attributes such as fresh vegetal, acidic and lower color saturation. Wine PA distribution followed a non-normal, Rayleigh-type distribution, with concentration peaks at mean degree of polymerization (mDP) 2 (22 to 27% of total PA mass) and at mDP 6-7 (12 to 17% of total PA mass). The overall effect of EM resulted in increased tannin extraction from seeds (73 to 80% of seed-derived tannins), lower anthocyanin content, and decreased wine color saturation. This effect was independent of the maturity level and the EtOH concentration. EM increased astringency by 25 to 34% relative to control wines, and either did not enhance aroma, or was found to decrease fruity aromas. Saignée increased the anthocyanin and tannin content during maceration, promoting the formation of polymeric pigments while favoring a comparable proportion of skin- and seed-derived tannins.