The Role of Oak in Winemaking

Do you want to know more about oak and winemaking? Here are the answers to some common questions…

Why is oak the preferred wood for making wine barrels in which wine is aged?
Oak is preferred because it is easily bent, strong enough to withstand wear and tear, slightly porous (which is desirable for aging wines since it enables gentle oxidation that increases flavor complexity), has an appropriate amount of tannin, and its aromatic qualities complement and enhance wine.

The impact that oak has on a wine depends upon not only the type of oak used, but also the way the barrels are made. For example, whether the wood is sawn or split, and the method used to dry the wood can reduce the amount of aromatic substances and harsh tannins in the wood. Barrel size is also a factor because it determines the amount of surface-area contact the wine has with the wood—the greater the oak to wine ratio, the more oak flavor imparted to the wine. Oak barrels generally lose their ability to impart flavor to wine after four to five years.

What types of oak are used in winemaking?
White oak is the preferred variety for winemaking; red oak is not used because it is too porous. Both American oaks (Quercus alba) and European oaks (Quercus robur and Quercus sessilis) are used, but different oak varieties impart different qualities to wine. For example, American oak has a looser grain, more pronounced aromatic qualities, and imparts a more “vanillin” quality to wine. European oak, by contrast, has a tighter grain and imparts flavors that are more subtle. Some winemakers even prefer specific varieties of oak from specific forests.

How does “toasting” as part of the barrel-making process impact the flavors imparted to wine?
Toasting refers to browning or charring the internal surface of the wine barrel. There are three degrees of toasting (light, medium and heavy), and the degree of toasting winemakers choose for their barrels is influenced by the type of wine to be aged and the qualities they want to impart to the wine being aged. The process of toasting accentuates the vanilla aroma of the oak and adds an additional smoky/spicy quality.

How much time should a wine spend aging in oak?
How much time a wine should spend aging in an oak barrel is a function of the grape variety, the intensity of the wine, and cultural flavor preferences. Oak flavors and tannins can overpower delicate wines, and such wines are not well suited to aging in oak for even a short period of time. Other wines can spend years aging in oak until they reach their peak. For example, Rioja can be aged in oak barrels for a decade.

Other than barrel aging, what methods are used to impart oak flavor to wine?
Oak chips or oak staves can be introduced into stainless steel tanks to impart oak flavors to wine. These methods tend to be used in the production of less expensive wines.