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August 2015 WINES&VINES 79 WINE EAST WINEMAKING How much tannin to add? Tannin vendors have always talked about "sacrificial tannins," or the percentage of any tannin addition that will be lost during wine processing. Empirical data from winemakers suggests that additions to hybrid wine fermen- tations should be anywhere from two to four times higher than the manufacturer's recommended ad- dition, which is geared for V. vinif- era wine production. In a study with Maréchal Foch, Corot Noir and Cabernet Franc (used as a representative V. vinif- era control), a condensed tannin product was added at crush at the recommended rate and at two and three times the recommended rate. Results showed that Caber- net Franc retained more tannin at all levels than did Corot Noir or Maréchal Foch, with the latter only retaining half as much as Cabernet Franc for the same ad- dition concentration. Further, a sensory panel showed no sensory difference in any of the wines, despite the vast range of addition, which suggests that higher additions can be made without contributing unpleasant flavor compounds. Appropriate addition rates and sensory impact will vary by grape cultivar and tan- nin product, however, so bench trials are always a good idea. And when to add it? Traditional wisdom dictates that winemakers apply all additions as early in the process as possible to allow wine components to "inte- grate." While this seems to make sense, in the case of tannin sorp- tion, it may run contrary to best practices. If the proteins that bind and remove tannin come from the grape, tannin sorption should de- crease as more grape material is removed from the wine. In other words, sorption activity is highest at crush and will decrease as press- ing and subsequent rackings re- move grape material. A series of studies at CEEL has shown this to be true, and that later tannin ad- ditions will result in a greater per- centage of tannin retained. Sensory studies are planned to see how addition time impacts wine aroma. But what about color? In addition to integration, wine- makers often voice concern about the formation of polymeric pig- ments, the anthocyanin-tannin complexes that are thought to provide stable color during wine aging. Since anthocyanins are at their highest concentration during the first few days of on-skin fer- mentation, one would deduce that tannin additions made early in the process would interact with more anthocyanins, leading to the most stable color. This may be true in V. vinifera, but we're unsure how stable color formation occurs in red hybrids. In addition to having different tannin compounds, most hybrid grapes have different anthocyanin compounds, and their binding af- finities and mechanisms are un- known. Until more research has been done, it's impossible to know whether early tannin additions will have any effect on stable color formation in red hybrid wines. Know your tannin additive Exogenous tannin additives are not created equal but fall into roughly three categories: grape- derived condensed tannins, plant (but non-grape)-derived con- densed or hydrolysable tannins, and any mixture of the two. Hy- drolysable tannins are commonly extracted from oak, acacia or the South American Quebracho tree. Producing high-purity tannin extracts is very difficult, so exoge- nous tannin products range from 10% to 45% tannin, with the re- mainder consisting of inseparable - B E C O PA D - Y E A S T & E N Z Y M E S - C R U S H PA D E Q U I P M E N T - S T E R I L E F I LT R AT I O N - W I N E R Y H O S E - O A K A LT E R N AT I V E S EASTERN WINE LABS Serving the Analytical needs of East Coast Wineries WWW.EASTERNWINELABS.COM Ph 609-859-4302 Cell 609-668-2854 chemist@easternwinelabs.com AOAC Member EasternWineLab_Mar09.qxp 1/22/09 9:47 AM Page 1 Bird Netting TANNIN RETENTION TRIALS Cultivar 400 ppm 800 ppm 1,200 ppm Maréchal Foch 30 55 110 Corot Noir 43 110 195 Cabernet Franc 50 110 220