Stag’s Leap Wine Cellars

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Stag’s Leap Wine Cellars

Winemaking Articles

How Do You Like Your Tannins?

Take a sip of over-steeped tea. Now taste a fine Napa Cabernet Sauvignon. The drying, bitter sensation from the tea is due to tannin—the same organic compound that gives the wine a firm structure and long, beautiful finish.

Tannins are phenolic compounds that help stabilize the color and contribute to the textural qualities in many fruits. In wine, tannins come mostly from the grape skins and seeds and from the oak barrels in which wine is aged. They react with the proteins in our mouths similarly to the way they react with the proteins in animal skins. Hence the name "tannin," which derives from their use in tanning leather.

In addition to contributing texture and complexity to wine, tannins are powerful antioxidants and play a critical role in wine aging. The trick is to have enough of the right kind of tannins without overwhelming the wine’s fruit qualities. The winemaker must understand the sources from which tannins come and use a judicious touch in their handling, since an overabundance of tannins will make wine harsh and bitter.

Tannin control begins in the vineyard. As fruit ripens, the tannins increase but their more astringent and bitter qualities diminish. Hence the importance of grooming vines throughout their lives and during each growing season to direct their energies away from leaf production and toward fruit ripening.

Once the grapes are harvested, the stems are removed to limit their vegetal and bitter tannic influence. As fermentation proceeds the skins provide color and flavor elements, including tannins that leach into the juice (aided by the heat the fermentation creates) as the juice is pumped over the skins that form a cap at the top of the tank. The winemaker can influence the tannin content in the finished wine by varying the pumpover regimes, the fermentation temperature, and how long the grape skins stay in the wine.

Tannins are likewise an important consideration in the pressing process. A winemaker whose goal is outstanding wine will keep the free run—wine that drains off the skins without any pressing—separate from wine that is pressed out of the skins in the beginning. The wine lots from each level of pressing are also kept separate, since lighter pressing will extract fewer of the harsher tannins remaining in the skins and seeds. These lots are then used in the blend to enhance the wine’s structure and complexity.

The oak barrel in which wine ages is another source of tannins. The age of the wood and the way the oak was cured and shaped all influence the character of the wood tannins, so the winemaker has many choices to make in selecting which barrels to use for each wine.

Tannins react with oxygen, another factor the winemaker must take into account. Too much oxygen can cause premature loss of both flavor and color, leaving the wine tasting flat or flabby. But the small amount of air the wine is exposed to during barrel aging helps to soften tannins in positive ways.

The aging process proceeds after the wine is bottled, and tannins continue to develop inside the bottle. Over time, tannins may form larger molecular structures with other elements in the wine, causing them to fall out of solution and become sediment.

A well-made wine will continue to improve with age even after sediments begin to form. In the realm of connoisseurship, one of the great aesthetic pleasures is enjoying the silky tannins of a well-crafted, well-aged wine.