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Tannins Are Important in Red Wine Production
Terry Sullivan

James A. Kennedy presented two sessions that dealt with tannins and red wine. Dr. Kennedy is a Professor and Chair of the viticulture and enology department at Fresno State University. Although his presentation slides contained images of the molecular structure of tannins, that can intimidate some, his presentation was very understandable.

Tannins are influential on all aspects of red wine including the color, aroma, taste, flavor, body and texture. Generally the higher concentration of phenolics influenced by tannins, the higher the price of the wine. Winegrowers and winemakers can control tannins in the vineyard, during fermentation and during aging. It is determined that seed tannins cause bitterness in the wine while skin tannins are more approachable.

In the vineyard, skin tannin development occurs prior to verasion. In a study done by Dr. Kennedy at Archery Summit Winery in the Willamette Valley of Oregon, two blocks of Pinot Noir were identified. Wine from one block currently sells in the $60 range while wine made from the Pinot Noir in the other block sales in the $100 - $120 range. The researchers concluded that skin tannin was more developed in the block where the vines had lower vigor. Since light exposure can influence vigor, light exposure between the two vineyards was studied. Skin tannins are more responsive to the environment than seed tannins. A question to ask is how much light exposure is needed in a particular area for the development of skin tannins.

Once the juice begins to ferment in the winery, skin tannins begin to change. The tannins are affected by acidity and oxidation. Studies indicate that the higher the skin tannins in wine the higher the price the wine will sell. Crushing the berries can optimize skin tannins. Optimal extraction of skin tannins levels off after fermenting for ten days. Tannins will soften with age. They also evolve over time. When tannins in a ten tear-old bottle of wine were compared to the tannin structure pre-verasion, the tannins only represented 10 percent of their pre-verasion structure.

In the vineyard, growers can take advantage of light to optimize the skin tannin development prior to veraison. In the winery, the winemaker can crush berries and closely monitor acidity and oxidation. Skin tannins yield to desirable phenolics and mouthfeel. The more developed skin tannins will fetch higher prices for the wine.

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