A wine barrel has become one of the most recognized symbols associated with wine. As a society we have romanced the wine barrel to the point where we have turned it into tables, benches, planters and candle holders. Case in point, I have two barrels in my wine cellar as leg supports for a table and I have a candle holder made from a barrel rib on my bar.
The Romans discovered that oak could be more easily bent into the traditional barrel shape than palm wood; the oak only needed minimal toasting and a barrel could be created much faster. Oak was also the most abundant in the forests of continental Europe and its tight grain made it waterproof.
The Romans learned that oak has a tendency to soften and smooth the flavour of wine and provide it with a more complex taste. Slight toasting of the wood added scents such as cloves, cinnamon, allspice or vanilla, as well as flavours such as caramel, vanilla or even butter.
Today wine barrels are made from a variety of materials; European oak (often referred to as French oak), American white oak, stainless steel, aluminum and HDPE (high-density polyethylene) plastic. These barrels typically come in 3 standard sizes:
- Bordeaux type – 225 litres
- Burgundy type – 228 litres
- Cognac type – 300 litres.
Barrel aging is the main element of what is referred to as the élevage process, which is a French term meaning “raising” or “upbringing”. This is what occurs 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 flavours integrate and mature.
The winemakers’ choices during the aging process include how long to age the wine for and how much to manipulate it. which has a major impact on the taste of the finished product. One of the most important choices is what type of barrel to age the wine in.
When oak barrels are manufactured they 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 smoky, roasted aromas.
An oak wine 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 flavour compounds with use so they must be replaced every few vintages.
In addition to adding oak flavours, new oak aging changes the tannin structure of red wines. Tannins from the wood barrel transfer into the wine, giving it a stronger structure. This contributes to a wine’s aging capability, 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, the oak will no longer provide flavour or tannin to the wine. The older barrels still allow for slow oxygenation, so they can be used to age wine that needs to mellow without the addition of oak flavouring.
Oak influences both red and white wines by adding the aroma of:
- Baking spices like cinnamon, clove, nutmeg
- Coconut (especially from American oak)
- Dill (especially from American oak)
Red wines may also present additional aromas of:
- Burnt sugar
Steel barrels, on the other hand, add no flavour to the wine. Steel simply stores the wine for a few months while it stabilises and the grape flavours 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 disappear when exposed to oxygen.
Stainless steel aging is used for wines that would not benefit from the addition of oak flavours or the softening effect that oak has on tannin. It is used for white wines not having tannins to manage. Stainless steel is the usual choice for aromatic and semi-aromatic white grapes including:
- Unoaked Chardonnay (often aged in oak as well)
- Grüner veltliner
- Pinot grigio
- Sauvignon blanc
For red wines, stainless steel is a good choice for lower tannin, fruity grapes such as:
- Baco Noir
Red wines aged in stainless steel are straightforward and juicy, with no oak flavours obscuring the flavours of the grapes.
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.
Since oak barrels can be used only two or three times for the purpose of adding flavour to the wine, the cost of buying new barrels is built into the higher prices of oak-aged wines. Some producers try to mimic the flavours of oak aging by adding less expensive oak chips to wines that are aged in stainless steel vessels. Oak chips add vanilla and spice notes but have no effect on a wine’s texture like oak barrels do.