Barrel Aging

New wine has a raw flavor and a strong, simple, fruity aroma. As the wine rests after fermentation, a host of chemical reactions slowly proceeds, and results in the development of balance and complexity in the flavor. If the wine is being held in a new wood barrel, it also absorbs various substances from the wood that either provide flavor directly—for example, vanilla-like vanillin and the coconut-woody oak lactones—or that modify the wine’s own flavor molecules. In traditional wine-making, the months during which the wine is racked and shifted from container to container are a time when the wine’s chemical evolution is directed by periodic exposure to the air. In the presence of oxygen, the tannins, anthocyanin pigments, and other phenolic compounds react with each other to form large complexes, so the wine’s astringency and bitterness decline. Some of the molecules that provide aroma break apart or react with oxygen and each other to form a new suite of aromas, so fruity, floral notes fade in favor of a more subdued general “wineyness.” White and light red wines are generally bottled young, after 6–12 months, with a fairly fresh, fruity bouquet, while astringent dark reds may require a year or two to develop and smooth out.