Practical Winery
65 Mitchell Blvd, San Rafael, CA 94903
phone: 415-453-9700 ext 102
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July/August 2009
While the fermentation rates were generally similar between treatments, some differences in the wines were noted. There were no differences in alcohol percent (v/v), TA, pH, or tartaric, malic, or lactic acids, between pigeage and délestage-produced wines (Table IV).
Total tannin, total phenols, and total anthocyanins were greater in pigeageproduced wines. Differences in absorbance at 420 nm + 520 nm, and 420 nm/520 nm, were noted between délestage and pigeage. Table II provides the concentration of selected phenol compounds on aged Cabernet Sauvignon. Significant differences among treatments were not observed.
Tannin concentrations remained stable until active fermentation, then increased and were higher in pigeage-produced wines at most
sample periods (Figure IV). Total phenols (AU280) increased for both treatments during pre-fermentation maceration, and significantly during fermentation (Figure V).
At dejuicing, the total phenol concentration in the press wines averaged 14.5% and 9.8% higher than free run for délestage and pigeage wines, respectively (data not shown). At the completion of fermentation, free-run pigeage-produced wines had higher absorbance at 420 nm + 520 nm, and lower 420 nm/520 nmabsorbance than délestage wine (Table IV).
During the cold soak period, the percentage of color from monomeric anthocyanins declined dramatically in the juice, then declined or remained constant for the first threedays of fermentation(FigureVI).
By sampling on day-10 (completion of alcoholic fermentation), the percentage of
monomeric pigments had declined for both treatments. At dejuicing, day-22, the percentage of color from monomeric pigments in the pigeage free-run wine averaged 33% higher than the délestage wine.
Press wines showed a similar trend (data not shown). The percentage of color fromsmall polymeric pigments increased during the cold soak period, remained or declined during the first five days of fermentation for both treatments, then increased slightly (Figure VII).
The percentage of color from large polymeric pigments increased during cold soak and fermentation for both pigeage and délestage treatments, and was slightly higher in the délestage wines at dejuicing (Figure VIII).
Post-fermentation, free-run Cabernet Sauvignon délestage and pigeage wines demonstrated 34.6% compared to 43.5% color from monomeric pigments, 53.8% compared to 49.6% color from SPP, and 11.6% compared to 6.9% color from LPP (Table IV), respectively.
Following cold soak, total glycoside concentration was greater in the pigeage than délestage tanks by an average of 49% (Table V). Total glycosides increased during fermentation (cold soak to day-10) for both treatments. By the completion of fermentation (day-10) and at dejuicing, total glycoside concentrations were similar in pigeage and délestage wines. Phenol-free glycosides were in higher concentrations in pigeage wines post-cold soak and at dejuicing.
Discrimination sensory analysis of Cabernet Sauvignon délestage- and pigeage-produced wines indicated differences in aroma and flavor. The principal component analysis (PCA) for aroma indicated variation among treatment replicates that accounted for 59% of the variance (Figure IX). The first and second principal component analysis of flavor accounted for 63% of the variance (Figure X).
A relatively high concentration of extractable seed tannins has been shown to negatively impact wine quality in Virginia and other wine-producing regions. The study was conducted using 1,416 kg lots, and seed removal in conjunction with délestage, to help improve red wine mouth feel.
Table III: Effect of manual cap punch (control) and délestage on total (TGG) and phenol-free (PFGG) Merlot glycosides for two seasons.
Figure IV
Figure IV. Effect of pigeage and délestage on Cabernet Sauvignon - tannin concentration during cold soak, fermentation, and post-fermentation; n = 3.
Figure V
Figure V. Effect of pigeage and délestage on Cabernet Sauvignon - total phenols during cold soak, fermentation, and post-fermentation; n = 3.