Photo by Sara Matthews
Wine aging in barrels at Chateau Margaux in Bordeaux. Barrel aging helps the flavors of blended wines knit together.
After racking, many wines are blended and barrel aged.
Blending: Grapes from different vineyards are frequently vinified separately. Some vineyards may yield more acidic wines or more fruity wines or wines with different flavors. Blending can also unite wines made from grapes at different ripeness levels and different clones, each with their own nuances. Blending these wines together can yield a single, more complex wine. On the other hand, if a vineyard or growing area has a distinctive character, also known as terroir, that can be conveyed by the wine, that wine is normally bottled separately and labeled with the vineyard name.
Barrel Aging: Prior to bottling, wines may be aged for a number of reasons. First, barrel aging allows the flavors in newly blended wines to knit together and become harmonious, losing the disjointed flavors that can appear immediately after blending. Second, with the highest quality wines, careful barrel aging can increase the wine's ability to age in the bottle.
Slight exposure to oxygen during barrel aging can add more flavors to red wine and soften the tannins. The tannins soften as tiny, angular tannin molecules agglomerate (or polymerize) to form larger, less angular molecules. The result is a more complex, weightier, silkier wine.
Exposure to oxygen during winemaking can cause white wines, on the other hand, to age prematurely, darkening and losing their fresh fruit flavors. White wine must therefore be protected from oxygen as much as possible. For this reason, whites are only minimally aged in tanks or barrels.
Filtration: Winemakers aiming to produce a crystal clear wine often filter the wine before bottling, while others avoid filtering because it may remove some flavor components. In this case, "Unfiltered" may appear on the label, indicating that the winemaker has opted to retain the fullest flavors possible, and that the wine is not expected to be brilliantly clear in the glass. Large production wineries frequently use filtration to produce crystal clear wines or to remove bacteria that might cause the wine to spoil in the bottle.