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w i inneeGMAKIN GG w R O WIN Photo by Wendy Day, Vine Cliff Winery MERLOT AND CABERNET SAUVIGNON WINES WITH PARTIAL SEED REMOVAL BY Bruce W. Zoecklein,1* Lisa M. Pélanne,2 Sandy S. Birkenmaier,3 Karen Reed4 *Emeritus professor, former head of the Enology Grape Chemistry Group, Virginia Tech, 2,3Research Associates, 4 viticultural consultant D élestage (rack and return) with partial seed removal was compared with manual cap punch down (three years) using Merlot, and with a mechanical punch-down (pigeage) system usi ng Caber net Sauvignon (one year). Fermentation reduced the color derived from monomeric pigments and increased polymeric pigment color for all treatments. Délestage wines generally had more color derived from large polymeric pigments compared to cap-punched or pigeage wines. Total glycosides increased during cold soak and fermentation and were in greater concentration in cappunched Merlot, and similar among Cabernet Sauvignon treatments. Discrimination testing (triangle difference analysis) demonstrated Merlot wines generally differed in aroma and/or flavor. Cabernet Sauvignon wines difThis text edited from first publication: Jan./Feb. 2009. fered in both aroma and flavor. Principal component analysis (PCA) for aroma and flavor demonstrated the variation among control and délestageproduced wines. Analysis of wine volatiles indicated that aromatic esters were generally found in highest concentrations in délestage wines which also demonstrated a decreased level of long chain or fusel alcohols. Grape phenol compounds The color, structure and aftertaste of red wines are mainly derived from the varied and complex impact of phenolic compounds. It is estimated that 50% or less of the total phenolic compounds present in the skins, seeds and flesh of grapes can be extracted during conventional winemaking.12,36 The level of extraction depends on various factors, including fruit maturity, duration of skin contact, temperature, ethanol concentration,20 and vinification practices, including cap management techniques.7,16,22,31 Therefore, understanding the quantitative and qualitative influences processing has on grape and wine phenolic compounds is important in premium wine production. Monomeric and polymeric flavan-3-ols comprise the majority of phenolic con- Aeration across a screen with seed removal during draining of the fermentor. stituents in red wines,30 being extracted from the skins and outer seed coat during fermentation.38 Polymeric flavan-3-ols, referred to as proanthocyanidins or condensed tannins, arise either by addition of intermediates from flavan-3,4-diols to flavan-3-ol monomers, or by acetaldehyde-induced polymerization.8,35 Grape seeds differ from skins in that seed proanthocyanidins contain greater levels of monomeric flavan-3-ols, and those esterified to gallic acid.5,25,32 Additionally, seed proanthocyanidins generally have a lower degree of polymerization (dp) than those found in skins, and no trihydroxylation of the B-ring.9 Proanthocyanidins are reactive molecules that may form complex species thought to impact wine sensory features. Monomeric and polymeric flavan-3-ols induce both astringent and bitter mouth sensations. S. Vidal et al. demonstrated that overall astringency increased with increases in dp. 38 Additionally, they reported that galloylation increased tannin coarseness, while trihydroxylation of the B-ring decreased coarseness. Tannins in the skins and seeds can combine with anthocyanidin glycosides (anthocyanins) to form polymeric pigments.36 These pigments are believed to be formed by condensation products of malvidin-3-glucoside and various procyanidins created through acetyl bridges.9,26 Anthocyanin-tannin complexes can be produced by binding between the C-4 of the flavylium salt and the C-8 of catechin.21,27 D.O. Adams et al. reported extractable seed tannins in Syrah grapes declined by about half from véraison to harvest, and were about three times greater than skin tannin concentrations.2 Grape skin phenols are more easily extracted during fermentation than those of seeds and stems.18 Although skins contain a lower concentration of total and polymeric phenols than seeds,13 they may be the primary source of polymeric phenols in wine.14 For the first five to seven days of fermentation, phenolic compounds are extracted mainly from skins, followed by extraction from seeds.23 Several reports have suggested that seeds contribute significant concentrations of proanthocyanidins to wines,15,29 while others have reported the seed contribution to be limited.4,24,39 These contradictory observations may be the result of differences in cultivar, fruit maturity, and pr actica l win ery & vin eya r d JANUARY 20 14 45