When you read the labels of wine bottles, sometimes it seems there is more attention paid to oak than to grapes. It's no surprise, because the use of oak can dramatically influence the liquid in the bottle.
Two important things happen to wine in oak barrels. First, the wine is exposed to a bit of oxygen. This is a good thing, softening reds especially. Second, the barrel may directly transfer flavors to the wine, increasing the complexity and appeal of the finished product.
Customers in the past couple of decades have approved of the use of oak. It's a rare day at most wine shops and restaurants when a guest doesn't request a chardonnay with noticeable oak flavor.
The creation of a wine barrel is an art. Wood is aged outside for a couple of years, formed by hand into a watertight vessel, then toasted over an open flame. When filled with wine, aromatic compounds released by the toasting process are transferred into the wine.
Barrels can be toasted lightly or deeply for desired flavors. The best known (and most loved) is vanilla, but oak can impart aromas like caramel, clove, coffee, cocoa, roasted nuts, coconut, butterscotch, cinnamon and toffee.
Like an artist, a winemaker chooses what kind of oak, when and to what degree to use it. Simply put, the newer the oak, the more flavor it gives, and the more the oak is in contact with the wine (meaning smaller barrels), the more flavor from the wood is imparted. As barrels get used over and over, their influence on the wine diminishes. Older or very large barrels may not impart much, if any, flavor.
Oaks from different parts of the world have different qualities. French oak is often considered the finest. Tightly grained, its flavors are subtle but distinct. Some connoisseurs can even tell from which forest in France a barrel was sourced by the flavors.
American oak tends to have a slightly bolder and more pronounced vanilla flavor, and is prized by winemakers working with full-flavored grapes. Oak also comes from other places in the world, notably Hungary, Slovenia, Poland and Russia.
When the winemaker uses oak also is important. Some use an oak barrel for fermenting wine, while others mature wine in oak after fermenting it in another vessel, such as stainless steel. A winemaker also might divide the wine, placing some in new oak and some in older oak, then blending the results. This is what winemakers mean when you see terms like "50% new oak."
Using oak has one huge drawback: It's terribly expensive. One new, top-of-the-line French barrel can run upward of $800. With an expensive oak barrel adding as much as 35 wholesale dollars to every case of wine, the use of new oak is a commitment. No wonder so much back-label copy is devoted to it.
