Wine 101: What Is Barrel Aging? Understanding the Barrel Aging Process in Winemaking and the Difference Between Steel and Oak Barrels

Barrel aging is the cornerstone of the process called élevage, which is the French term meaning “raising” or “upbringing” used to describe what happens to the wine between fermentation and bottling. The wine’s élevage can last for a few months to many years, during which time the wine’s flavors integrate and mature. The winemakers’ choices during the aging process, including how long to age the wine and how much to manipulate it, will have a huge impact on the taste of the finished product. One of the most important choices is whether to age the wine in steel or oak barrels.

There are two main types of oak that can be used to make barrels for use all over the world.: American white oak and European oak. However, European oak barrels are not exclusive to European winemakers and vice-versa. For example, American oak’s stronger flavors are a key component of the wines of Rioja in Spain.

Oak barrels are made from staves, which are long pieces of oak wood that are fitted tightly together with metal hoops. The barrels are toasted over a fire to either a light, medium, or dark toast level. New barrels with a light toast will give lots of vanilla and caramel notes, while a darker toast will give smokey, roasted aromas.

For oak wine barrels, the barrel’s age and size affect the amount of oak flavor that will be transmitted to the wine. Smaller barrels impart more oak flavor because they allow more contact between the wood and the wine. Oak barrels lose their signature flavor compounds with use, so they must be replaced every few vintages.

In addition to adding oak flavors, new oak aging changes the tannin structure of red wines. Tannins from the wood transfer into the wine, giving it a stronger structure. This contributes to a wine’s ageability, or longevity in the bottle. The wood also helps stabilize the tannins from the grape skins, giving them a silkier texture.

After a few years of use, new oak becomes “neutral,” and no longer imparts flavor or tannin to the wine. These neutral barrels still allow for slow oxygenation, so they can be used to age wine that needs to mellow without any oak flavor.

Once the wine barrel has lived its full lifespan in the winery, the creative wine enthusiast can repurpose a used wine barrel into a table top, a bar stool, or a wine barrel planter. Along with wooden wine boxes, solid oak barrel staves make great fuel for a backyard fire pit.

New oak aging adds these aromas to both red and white wines:

• Vanilla
• Caramel
• Baking spices like cinnamon, clove, nutmeg
• Coconut (especially from American oak)
• Dill (especially from American oak)

Additionally, you may find these notes in red wine aged in new oak:

• Smoke
• Chocolate
• Coffee
• Toffee/burnt sugar

Steel barrels are a type of barrel made from stainless steel used to age wine. The steel imparts no flavor to the wine: it merely holds the wine for a few months while it stabilises and the flavors integrate. Steel barrels also don’t let any oxygen come into contact with the wine. This kind of aging helps wines retain the fresh fruit aromas that degrade with exposure to oxygen.

Winemakers use stainless steel aging for wines that would not benefit from the addition of oak flavors or the softening effect that oak has on tannin. It is more popular for white wines, which, unlike reds, do not have tannins to manage. Stainless steel is the usual choice for aromatic and semi-aromatic white grapes including:

• Sauvignon blanc
• Riesling
• Gewürztraminer
• Pinot grigio
• Albariño
• Grüner veltliner
• Chardonnay (a versatile grape that is commonly aged in oak as well!)

For red wines, stainless steel is a good choice for lower tannin, fruity grapes like:

• Gamay
• Grenache
• Cabernet franc

Red wines aged in stainless steel are straightforward and juicy, with no oak flavors obscuring the flavors of the grapes.

The main difference between stainless steel and oak aged wines is the absence or presence of oak aromas and flavors. Certain grapes respond better to the different aging regimens. Neutral grapes (like chardonnay, which doesn’t have much aroma), will often be aged in oak to give them more complexity. Stainless steel aging is more appropriate for aromatic grapes (like riesling) whose distinctive aromas would be lost under the flavors of oak aging.

Another difference between stainless steel aged wine and oak barrel aged wine is price. Stainless steel aging is significantly less expensive than using oak because unlike oak barrels, steel barrels can be reused indefinitely and are much easier to clean. Stainless steel aging also takes less time than oak aging, which saves winemakers crucial space in the wine cellar. These factors mean that wines made in stainless steel are likely to cost less for the consumer.

New oak barrels can be used only two or three times to impart flavor to the wine, so the cost of buying new barrels is built into the higher prices of oak-aged wines. Some producers try to mimic the flavors of oak aging with less cost by adding oak chips to wines that are aging in stainless steel vessels. Oak chips add vanilla and spice notes, but have no effect on a wine’s texture like oak barrels do.

Learn more about wine appreciation in James Suckling’s MasterClass.