In an earlier post I wrote about the flavor and aromatic differences in two newly released La Rochelle Pinot Noirs. Though made from the same fruit and in the same way, the Pommard Clone in
American oak differed greatly from the same wine aged in
French oak.
While much of the differences in wine owe to the winemaker's hand, the actual structure of the trees made into barrels in France and the US is responsible for the "macro" characteristics of grain tightness, aromatics, flavors, and durability, among others. With the advent of improved curing regimes for American oak, qualitative difference between domestic and imported barrels are much less than they used to be.
Wooden receptacles have been used to store and age wine for hundreds of years, at least since the 1600s. We think of the 60-gallon barrel (or
barrique) when we think of wood, but large wood upright tank made of redwood are still in use today. Chestnut has also been used for aging wine, and
Balsamic vinegar starts as Trebbiano and is aged in a series of different woods to provide much of its flavor.
Oak is uniquely qualified for aging fine wine because of its relatively neutral aroma and flavor (compared to Redwood), its tightness of grain (Chestnut is not used much anymore because its porosity allows too much wine to evaporate), and its ability to bend without breaking (steam and fire are used to bend staves as barrels are being made).
White oak,
Quercus alba, is the species of oak grown in America used for barrels;
Quercus sessilis, is the European species. Midwest and Eastern states produce nearly all American barrels, with Missouri leading production. the map to the right shows production areas.
Quercus alba differs structurally from Q. sessilis in the number of tyloses it contains. A
tylose is a cellular structure in the xylem of the tree that blocks the nutrient-carrying tubes that run from the root up the tree, making the wood watertight. The American species has significantly more tyloses so the staves can be milled from larger sections of tree and up to 50% of the tree will be usable for barrel making. The European species, with fewer tyloses, needs to be handsplit into staves along the tylose lines, and up to 80% of the wood is wasted.
American oak barrels, as a consequence, are less porous than French oak and less tannic. At the same time, American oak is significantly more odorous than the French counterpart, contributing aromas of vanilla and coconut while the less powerful spice aromas of clove, and cinnamon are a feature of French oak.
French oak is used in large part because it tends to bolster the mid-palate of the wine, providing a sense of roundness and shape (just as it does in the La Rochelle Pommard clone Pinot Noir).
At La Rochelle, we tend to uses significantly more French than American oak. The aromatics of French oak and the structuring effects of French barrels work better with a majority of the Pinot Noir we harvest. For our Cabernet brand, American oak is often used because the depth of Cab fruit stands up well to the powerful aromatics.
A great deal of the improvement in American oak can be attributed to the air-drying of staves. French coopers have been doing this for centuries, but it is much newer for American coopers. In the early 20th century whiskey producers used newly sawn wood from which to make barrels. The extremely high tannin level and balsamy quality of the wood was overwhelmed by the product inside. Recently, American coopers have been air-drying their
barrel staves for 24-36 months, stacking the wood, open to the elements, so that as the wood gets wet then dries many times over the course of time, much of the tannin and sappy quality of the wood is leeched out.
Toast levels of the barrels also add significantly to the aromatics, flavor, and quality of wine. the better barrels are toasted over an open fire both to bend those staves into a barrel shape and to bring out specific flavors and aromas in the wine. It is known that specific flavor elements such as coffee and chocolate are created in the wood at various temperatures and toasting durations. Depending upon the type of wine being made, we will buy barrels that have undergone medium, medium-plus, and slow heavy toasting so that we can capture
these organoleptic elements in the finished product.
While American oak was originally seen as a poor man's alternative to French oak, its recent quality and the characteristics it brings to wine aging make it a very valuable tool in the wine maker's arsenal.
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