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January 2015 Wines&Vines 155 wine east winemaking Eaton's BECOPAD ® depth filter sheets provide excellent filtration while maximizing throughput. It's the choice for winemakers who demand high capacity, minimal drip loss and virtually no color adsorption. Visit www.eaton.com/wine or contact Marge DeAngelis 732-212-4703. Get the Clear Advantage F I LT R AT I O N P R E C I S I O N and elongate the tannin chains and the fre- quency and linkage type of any branches. At present, scientists are unable to isolate indi- vidual condensed tannin compounds for iden- tification and quantification. Instead, condensed tannins must be measured indi- rectly by chemically breaking apart the chains and looking at the pieces—a bit like trying to figure out what a jigsaw puzzle looks like by examining each puzzle piece individually. For this reason, tannin content in grapes and wine is generally reported as overall concentration and mean degree of polymerization (mDP), since it's impossible to quantify individual tan- nin compounds. The second type, called hydrolysable tan- nins, is wood-derived and historically found only in barrel-aged wines. Grape and wood- derived tannin types aren't interchange- able; condensed tannins bind with proteins at a rate of about 20:1 in reac- tions independent of temperature and ethanol content, and have the potential to bind with anthocyanins in color- stabilizing reactions. In contrast, hydro- lysable tannins bind with proteins at a rate of around 40:1 in reactions that increase with temperature and decrease as ethanol content increases, and are not known to participate in polymeric pigment reactions. In short, condensed tannins should aid in color stabilization and provide a higher perception of astringency, while hydrolyzed tannins will be less likely to stabilize color but may promote fuller mid- palate and a softer mouthfeel due to lower, slower protein interaction. Starting at véraison, tannin length (mDP) increases and perception of bitterness de- creases as grapes mature, but extractability decreases, making optimal harvest time a bal- ance between tannin quality and quantity. Ex- traction during maceration and fermentation is another balancing act, as skin tannins are extracted rapidly during early alcoholic fer- mentation but eventually plateau, while seed tannin is extracted slowly and consistently throughout. Since a higher proportion of skin- derived tannins has been found to enhance perception of red wine quality, winemakers must optimize both quantity and proportion of skin and seed tannins extracted. Additional studies suggest that warmer fermentation and saignée favor overall extraction, and that the latter results in higher average mDP. Both punch down and pump over enhance tannin extraction, but the degree and type seem to vary by cultivar and method. Tannin woes Low tannin concentration and poor tannin quality are common complaints of red wine producers, and at least one study suggests that this emphasis on polyphenolics is well founded, since as much as 70% of total vari- ance among red wines as been attributed to tannin astringency. Unfortunately, recent re- search suggests that both of these pa- rameters are more complicated than traditionally thought, and means of both assessing and influencing tannin quantity and quality are anything but straightforward. While it would seem that final wine tannin concentration equals whatever percentage of tannin can be extracted from the grape, a number of obstacles prevent a direct translation from grape to wine. A recent survey comparing wine tannin to tannin per berry in a range of EFFECT OF TANNIN TYPE grape derived wood derived Tannin: protein binding ratio 20:1 40:1 Impact of temperature Temperature independent binding Temperature binding Impact of ethanol Ethanol independent binding Ethanol binding Impact on color stability Potential color stabilization activity No known potential for color stabilization