Tannin alert: a new tool to improve wine quality

 For a great take on tannins, look to none other than Beppi Crosariol, the Globe and Mail’s wine columnist.

How does that taste? Richie Roberts (L), winemaker for Fielding Estate Winery, compares notes with owner-grower Curtis Fielding and Belinda Kemp, senior scientist, oenology for Cool Climate Oenology and Viticulture Institute (CCOVI). Mid-October was a good time to sample these Merlot grapes, still two weeks away from harvest. CCOVI is developing a tannin alert for Niagara peninsula growers that could eventually be rolled out across the province. Photo by Denis Cahill.

“They’re astringent, sometimes furry-tasting compounds found mainly in red wines,” he wrote in an October 2012 article. “They’re never a bad thing where quality is concerned. In fact, some of the greatest, most cellar-worthy wines are strongly tannic. But like the bristly texture of a wool sweater, they can bother some consumers. Naturally produced by plants, tannins get into the juice by way of grape skins, seeds and stems.”

For Richie Roberts, winemaker at Fielding Estate Winery, massaging those furry-tasting compounds is totally in order depending on the growing season at Beamsville, Ontario. If the right balance isn’t reached – too much tannin from seeds and not enough from skins, for example-- the results are light-coloured wine, lack-lustre flavours and green aromas.

Belinda Kemp is trying to help winemakers find the best way to tweak tannins. As the senior scientist in oenology for the Cool Climate Oenology and Viticulture Institute (CCOVI), she’s testing the tannin concentrations in skins and seeds so that she can suggest different wine-making techniques. With the first season of testing complete, she’s looking to launch a tannin alert service in 2014 that would be the first of its kind for the Niagara region. If successful, it could be rolled out across Canada.

To date, winemaking decisions have been based on sugars, titratable acidity and pH levels. She plans to add more critical data with vineyard sampling and laboratory testing of tannin concentrations in three red varietals: Pinot Noir, Cabernet Sauvignon and Cabernet Franc.

As she demonstrated in the Fielding Estate vineyard, brown seeds do not give a clear indication of ripeness.

“There is no such thing as tannin maturity,” she says. “Just a difference in extractable tannin concentrations. There can be a tiny change in brix level and yet a big change in tannin levels. We want more skin and less seed tannins. We want a high per cent of brown seeds rather than green ones that can negatively impact flavour with green, unripe notes.”

With more information at harvest time, winemakers can employ a number of techniques to soften the impact of tannins and to improve wine quality at all ripeness levels. Kemp is now analyzing the samples to set a benchmark. Based on concentration data, grape skins and seeds will be classified into one of three categories: low, medium or high tannin levels.

A year from now, base-level wines from the three grape varieties will be made at the low, medium and high tannin levels using the same winemaking technique. A second set of wines will be produced using the most suitable winemaking techniques for each tannin group which can then be compared to the base wines. Next year, winemakers should be able to taste and see the differences in wines.

As more knowledge of Niagara grape tannin is gained, Kemp plans to issue a best practices guide for managing tannin concentrations in red wine. Curtis Fielding, for one, is looking forward to a tannin alert as a tool in addition to the varietal information that’s available on brix, acidity and pH levels.

“We watch that barometer closely to gain a good perspective on what’s happening in the Niagara peninsula,” says Fielding. “We’re very pleased with the research coming out of Brock University. Their researchers are working hand-in-hand with growers and winemakers.”


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