Article & Photos by Greg Gonnerman
Oak and wine are such a natural combination that it’s easy to forget that through most of the history of winemaking, this combination was virtually unknown. Although there’s evidence of wood barrels dating back about 2000 years, oak wine barrels weren’t widely used until the 13th century. French boat builders of that time were familiar with bending and shaping oak, and they applied this knowledge to barrel construction. Before that, a variety of wooden and animal skin vessels were used, and up until about the 7th century CE ceramic vessels, called amphoras, were ubiquitous. Ancient shipwrecks are frequently found with hundreds or thousands of these amphoras stacked in their decayed hulls.
Barrel makers (coopers) have experimented with other woods for barrel construction, but nothing has worked as well as oak. The early users of oak barrels likely discovered the benefits of barrel aging quickly. Not only does oak impart vanilla and wood flavors that complement most wines, but aging in barrels also allows for the slow infusion of oxygen which can be very beneficial. This natural micro-oxygenation can help soften the impression of tannins on the palate. Barrel aging also helps concentrate flavors due to evaporation through the wood.
Some home winemakers assume that barrel aging is the sole domain of commercial winemakers since the most common barrel sizes are quite large. However, there are a number of coopers now producing barrels in a range of sizes with some as small as three gallons. Home winemakers wanting to take the leap into barrel aging need to be prepared to test SO2 (sulfite) levels since the loss of SO2 can be dramatic and unpredictable when wine is aged in barrels.
There are several different species of oak used for barrels. American (Quercus alba) and French (Quercus robur and Quercus petraea/sessile) are among the most popular. Canadian oak is the same species as American, but some prefer it since trees grow more slowly and have a tighter grain when grown in a colder climate. Hungarian, Russian, and Slavonian oak are actually the same species as French, but differences in soil and weather can give these varieties their own unique qualities.
European oak varieties are generally favored among winemakers. American oak tends to impart stronger oak and vanilla flavors that may overpower some wines. Some suggest that the cause isn’t the species, but rather the way in which the wood is aged or the barrels are coopered. For some winemakers though, American oak is preferred. It has long been popular for barrel aging of Australian Shiraz and at least one maker of premium California Cabernet uses it exclusively.
To get the flavor of oak, winemakers need not use barrels. Oak additives or adjuncts are available in a wide variety of types and toast levels. The most popular forms are powders (sawdust), chips, cubes and spirals. Generally, the smaller the pieces the more quickly the oak imparts its flavor. Powders are often used pre-ferment while cubes or spirals are used for extended aging. Oak spirals have become increasingly popular among home winemakers in recent years as the flavor they impart closely matches that of a barrel. The least popular oak additive is liquid extract. While some report good results with these liquid extracts, most find that they impart undesirable creosote or synthetic flavors.
There are also a number of grape and oak tannin products that can be added to enhance wine structure or improve color stability. Tan’Cor Grand Cru and Fermotan are two such products. These can be used instead of, or in combination with, oak.
Oak aging is typically reserved for red wines. Some white wines may, however, be fermented on oak, with Chardonnay being treated this way the most frequently. Many white grape varieties have stronger fruit and floral notes that would compete with the vanilla notes imparted by oak. Chardonnay is among the least flavorful white grape varieties, and as such it takes oak quite well.
Woods other than oak have been used for wine barrels, including chestnut, pine, redwood and acacia, among others. Most were abandoned long ago in favor of oak, but cherry is still used in a limited fashion for aging Italian Amarone, and acacia barrels are gaining acceptance for the aging of certain white wines. Although commercial winemakers may be constrained by consumer expectations, hobbyists are free to experiment with different types of wood. Several in Texas have been using mesquite chips with great success and others are experimenting with apple, hickory, mulberry and other wood varieties. If you do decide to experiment, make sure to check its suitability (i.e. non-poisonous).
There are many options available for oak aging for both the hobbyist and commercial winemaker. The judicious use of oak can greatly enhance color and flavor — making a good wine into a great wine.
Greg Gonnerman is an amateur grape grower and winemaker in Mesa, Arizona, and he’s also a founding member of AZ Wine Makers
(www.azwinemakers.com). Check out his “Ask The Experts” blog here on Arizona Vines & Wines.