Wine may be fermented and aged in a variety of materials including stainless steel, oak and ceramic vessels, including concrete. The use of oak barrels is very common and its use dates back to the early days of Roman wine making.
While stainless steel imparts no additional flavor to a wine, and ceramics and concrete can add hints of minerality, oak barrels can have influences that range from subtle to intense.
When wine is aged in oak barrels, it develops flavors from the wood. Most commonly, oak barrels result in vanilla flavor that works well with many white and red wines. Oak barrels may also be toasted on their insides to varying degrees, and that adds smoky or toasty flavor to the wine.
If a wine is aged in 100% new oak, it will likely be very bold, rich, spicy and, of course, oaky. But, wines pull these flavors out of barrels relatively quickly. After the first year of use, a barrel loses much of its flavoring ability and, after three vintages, the wine has extracted most all of the oak's flavors, thus it is considered neutral oak.
Wines may still be fermented or aged in neutral barrels. Such aging tends to soften wines, particularly tannic wines, without adding the extra flavors. Neutral oak is typically used to maintain the fruit qualities in a wine while still getting some of the other benefits of aging in oak.
Next time we'll look a bit further into the process of 'toasting' the inside of an oak barrel. Until then, Cheers!