Practical Winery
65 Mitchell Blvd, San Rafael, CA 94903
phone: 415-453-9700 ext 102
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July/August 2009
Délestage: Step 1
Délestage: Step 2
Figure I. Effect of cold soak, fermentation, and post-fermentation on total phenols of control (cap punched) and délestage produced Merlot wines in season 3; n = 3.
was described. Evaluation was done based on olfactory (aroma) and retronasal aroma andmouthfeel (referred to as flavor). Evaluations of aroma and flavor occurred at different times.
Descriptive analysis was performed nine months post-fermentation on non-pooled Cabernet Sauvignon wine treatment replicates, using 11 trained panelists as described byM.Meilgaard et al.17 Panel members evaluated three replications of the two products (pigeage and délestage) six times.
Panelists had one to 10 years experience in descriptive or consensus sensory analysis. A list of descriptors was developed from three pre-evaluation training sessions with standards used for training prepared as reported by B. Zoecklein et al.43
Statistical analysis Results
The Merlot fruit averaged 21.5° Brix, 3.7 pH and 5.62 TA for the three years, typical of the region. Berries averaged 1.18 g, with 2.4 seeds, for the three seasons of this study. In years 2 and 3, Merlot fruit monomeric pigments were responsible for an average of 70.5%, SPP 19.7%, and LPP 9.8% of the total color.
By the end of délestage-treated fermentations, an average 25% of seeds had been removed each year. Fermentation rates were similar among treatments. Total phenols, estimated by the absorbance at 280 nm, increased linearly from crush until dejuicing for both délestage and control wines (Figure I). At day-six (dryness), control lots had a total phenol concentration slightly greater (7.7%) than the délestage (typical of this study).
CABERNET SAUVIGNON fruit (18,144 kg) grown in northern Virginia was hand-harvested at 23° Brix, and immediately destemmed, crushed, sulfur dioxide (30 mg/L) added, fermentable nitrogen levels were measured and adjusted, and itwas divided into treatment lots (as described above). Musts were given a cold maceration (cold soak) period of 48 hours at 10°C prior to fermentation, and yeasted (as described above).
Treatments consisted of 1) control, fermentation using a 10,000-Lmechanical pigeage, or 2) délestage, conducted in similar size and shape conventional stainless steel fermentation tanks (fill height to diameter ratio, 1:1).
Pigeage consisted of punching three times daily, 10 minutes per punch, with punching consisting of cycles of one minute down and 30 seconds up. Délestage was conducted daily as described above with the following exception: liquid was drained onto a flat tray (0.75 x 1.2m)with a screen (2.39mm diameter holes). Fermentationswere conducted at an average liquid temperature of 27°C(range 26° to 33°C) and an average cap temperature of 30°C (range 28° to 34°C). Mechanical punching and délestagewere conducted for seven days.
Pressing was performed post-dryness (2.0 g/L reducing sugar), 22 days following the beginning of fermentation,with a 5,000-L tank press, by allowing free drainage for one hour, followed by pressing to one bar. Free-run and press-run wines were not combined.
Chemical analysis
General fruit,must, and wine chemistries were conducted as described by B. Zoecklein et al.43
HPLC analysis was conducted 18 months post-fermentation on selected phenols in finished agedwines described by Price et al.19
Total tannins (catechin equivalents), and the percentage of color from monomeric pigments, small polymeric pigments, and large polymeric pigments was estimated using the procedures of Adams and Harbertson,1 and Harbertson et al.11 The concentration of total glycosides was estimated by the analysis of glycosyl-glucose in thawed samples as described by P. J. Williams et al.,41 and modified by R. S. Whiton and B.W. Zoecklein.40 Analysis of phenol- free glycosides was conducted as described by B. Zoecklein et al.44
Sensory analysis
Discrimination testing was performed on pooled wine replicates of Merlot and Cabernet Sauvignon, using triangle difference comparison described by M. Meilgaard et al.17 The wines were evaluated six to eight months post-fermentation in the Virginia Tech wine sensory laboratory, under controlled conditions that included red lighting to help eliminate color bias.
Panel membership required regular wine consumption (at least one glass per week) and attendance at two informational sessionswhere themethodology of evaluation