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78 WINES&VINES August 2015 WINEMAKING WINE EAST right growth habit and balanced harvest chemistry, its tannins and anthocyanins are going to give it away. The problem has been that, like any good agent of disguise, science has just been one step be- hind the masquerade…until now! Tannins All grapes—vinifera and hybrid— produce tannins in their skins and seeds. In absolute numbers, the concentration of tannins in seeds is much higher than in skins, but only a fraction can be extracted without strong chemicals and physical manipulation. Subse- quently, most of the tannins found in wine come from grape skins. All grape-derived or "con- densed" tannins are long chains of smaller phenolic subunits, or monomers, called flavan-3-ols. There are specific types, combina- tions and ratios of monomers found in wine, and individual tannin poly- mers vary by types of initiator units (the flavan-3-ol subunit that starts the polymer chain), elongator units (the subunits that build on to the initiators) and the ways that the polymers branch (or don't). One frustrating thing about these con- densed tannins is that there's no good way to identify and quantify them. At present, all we can do is run some chemical reactions that cut the chains into little pieces, tag the ends of the pieces, and then measure their average size. This analysis gives us an idea of the mean degree of polymerization (or mDP) of all the tannins in a wine, but it doesn't tell us the concentra- tion of any given size of tannin. Why hybrids are different Hybrid red wines tend to have low tannin, and the tannins that they do have are generally smaller (less than 4 mDP) than those found in red V. vinifera wines (7-13 mDP). Since polymers with an mDP less than 5 are usually more bitter than astringent, the sensory im- pact of these small-chain tannins is likely to add unpleasant sensory characteristics to the wine. Wine tannin ≠ grape tannin The lower tannin concentration in red wines led to a long-held belief that hybrid grapes also had low tannin concentration, because if the tannins were there, they would eventually be extracted with ex- tended maceration, right? In fact, analysis shows that while many hybrid grapes may have lower tan- nin concentration than V. vinifera cultivars traditionally responsible for "big" red wines (e.g., Cabernet Sauvignon), there's no correlation between berry tannin and wine tannin (Springer & Sacks, 2014). To work around this difficulty, Springer and Sacks propose that cultivars be evaluated in terms of tannin extractability using the fol- lowing equation: (wine tannin/grape tannin) X 100 When tannin concentrations are plugged into this equation, the data makes a bit more sense. Cab- ernet Sauvignon, for instance, has very high tannin extractability, and almost all V. vinifera have higher tannin extractability than hybrid cultivars. All bound up; no place to go The question is: What dictates tan- nin extractability? If there's not a direct path from grape tannin and wine tannin, understanding the factors that govern the movement of tannin from grape to wine can make a big difference in winemak- ing choices. Recent research sug- gests that the biggest factor isn't extraction method but rather the re-uptake of tannin by compounds that occur naturally in the grape. Pectin plays a small part, but pro- teins—and likely the same ones that provide disease resistance— seem to have the largest binding effect. If this is found to be true, it suggests a big problem: that the same attribute that allows hybrids to thrive in challenging environ- ments inherently handicaps the winemaker. The solution seems easy: just add tannin! As it turns out, just adding more tannin isn't enough. If the binding compounds are still in the wine, any tannin that's added will just be sucked right back out. In order to make good red hybrid wine, then, there are two challenges: First: Tannin has to be added to the wine, and sec- ond: Sorption activity has to be avoided or defeated so that the tannin stays in the wine. Natural Corks Champagne Corks Twinline Corks Bartops VISION Synthetic Corks G-Cap® Screw Caps Sales Representatives: Chris & Liz Stamp info@lakewoodcork.com lakewoodcork.com 4024 State Route 14 Watkins Glen, NY 14891 607-535-9252 607-535-6656 Fax PIONEER INNOVATOR PARTNER