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58 WINES&VINES September 2016 WINEMAKING PRACTICAL WINERY & VINEYARD fruit with 21 o Brix in the cooler 2011 vintage, but only marginally higher visual seed maturity at 25 o Brix than the unripe fruit at 21 o Brix during 2011 (see "Comparing Seed Maturity and Tannins"). Artificial manipulation of the sugar con- tent in both unripe and ripe fruit by means of chaptalization and water-back allowed us to tease out the effect of fruit maturity on tannin extraction independently from that of ethanol levels resulting from Brix increase in ripe fruit. Differences in EtOH as high as 2.7% (v/v) during maceration had no effect on tannin extraction in the EtOH (11.7%-14.4% v/v). However, previous research in model wines suggest counter, indicating that increas- ing EtOH from 0% to 6.5% and then to 13% EtOH (v/v) facilitates both anthocyanin and tannin extraction. 4 Contrasting findings in model wines with those obtained in actual winemaking condi- tions bring about a new set of observations and yet-to-be answered questions. First, model wines—while useful to model extraction of selected phenolics—disregard the effect of temperature and other wine matrix compo- nents such as anthocyanins and polysaccha- rides that may, in turn, affect the fate of tannins into the wine matrix. In the present work, we assimilate this matrix effect as the proportion of missing tannins that cannot be found in the pomace after maceration and in the wines. We found that the proportion of tannin "bound" was more prominent in ripe fruit than unripe fruit and in extended-maceration wines rather than in control wines. We have evidence that this matrix effect also occurs in Cabernet Sauvignon wines. 7 Our findings suggest there may be a certain threshold of required EtOH to allow effective tannin extraction from seeds. Above that threshold, further increases in EtOH cause little effect. We observed tannin extraction at EtOH levels as low as 11.7%, and the longer the maceration length, the higher the propor- tion of seed-derived tannins both at 11.7% and 14.4% EtOH, suggesting that maceration length and not differences in EtOH was the factor responsible for the observed changes. Either 11.7% represents the lower end of EtOH required to dissolve the lipidic outer coat of the seed and/or it presents the mini- mum EtOH level to disrupt hydrogen bond interactions between previously extracted tannins and cell wall materials toward the end of extended maceration, thereby furthering seed tannin extraction. While we evaluated an ethanol range be- tween 11.7% and 14.4% EtOH, it is unclear if EtOH levels above 15% will yield similar results. Ethanol levels as high as 15.5% and even 16% are not uncommon in warmer viticultural re- gions, and thus seed and skin tannin extraction under these conditions should also be studied. Expected outcomes of extended maceration include lower anthocyanins and wine color saturation and higher extraction of seed tannins into wine (and higher perceived astringency); these outcomes were confirmed in this study. Extended maceration results in lower color saturation due to progressive loss of anthocya- nins, perhaps due to oxidation; polymerization of monomeric anthocyanins into polymeric pigments and pyranoanthocyanins, and pro- gressive binding of anthocyanins to fermenta- tion solids (skins, seeds and stems, if present). Extended maceration decreased fruitiness and shifted aromas toward cooked and vegetal overtones (see "Sensory Attributes of 2011 Merlot Harvest"). The practice of extended maceration may have resulted in the accumula- tion of acetaldehyde, which may decrease perceived fruitiness. Increasing skin contact time may result in the loss of fruity nor-iso- prenoids such as β-damascenone. 2 One question this study sought to answer was whether the outcome of extended macera- tion would be contingent upon fruit maturity at harvest. Our research suggests that tannin extraction into wine during extended macera- tion is not only independent of EtOH (in the range of 11.7%-14.4%, as stated above) it is, more importantly, also independent of fruit maturity in the range of 20 o -24.5 o Brix. In practical terms, even if harvest is delayed, extended maceration should extract a predict- able proportion of skin- (about 20%-25%) and seed-derived tannins (about 75%-80%). An increasing body of research has shown the critical role that grape maturity plays on the sensory profile of a resulting wine. Riper fruit has been found to yield wines of improved chemical and sensory features than wines made from unripe fruit. 2,10 It is not without reason that winemakers devote substantial effort to chemically and sensorially gauge fruit maturity and establish precise harvest decisions. These results support both this prevailing notion in our industry along with previous research on the topic. Tannins, aroma and aroma precursors, anthocyanins, native polysaccharides, sugars and acids all evolve during ripening. Expect- edly, and consistent with the above research, we found that wines made from ripe fruit had higher color saturation, more fruit-forward aromas, less vegetal and earthy aromas, less sourness and a more viscous mouthfeel (but not less astringency than wines made from unripe fruit (see "Sensory Attributes of the 2011 Merlot Harvest). Early Harvest Late Harvest 2011 Season 2012 Season Concentration: 3.14 ± 0.2 b Seed color: 4.20 ± 0.07 c Concentration: 2.97 ± 0.1 c Seed color: 5.45 ± 0.20 a Concentration: 3.69 ± 0.3 a Seed color: 3.78 ± 0.03 d Concentration: 3.15 ± 0.1 b Seed color: 4.76 ± 0.08 b COMPARING SEED MATURITY AND TANNINS Visual seed maturity and tannin concentration of Merlot seeds at two maturity levels in 2011 and 2012. Concentration values in mg/g fresh weight (purple) and seed color values (black). Letters (a, b, c, d) within a type color are significantly different.