Rethinking American vs. French oak

Wines & Vines, Nov, 1992 by Jordan P. Ross

Many of the world's prized wines are aged in wooden casks or barrels. While there are other determinants of a wine's quality, such as the vineyard and the skill of the winemaker, the period of up to several years in wooden "cooperage" or barrels has a tremendous influence on ultimate wine character.

Wine is aged in wooden barrels as opposed to stainless steel tanks for two principal reasons: to enhance the flavor, aroma and complexity of the wine through the extraction of substances from the wood into the wine, and to allow air (oxygen) to come in contact with the wine to allow a slow, gradual oxidation process. The particular influence of barrel aging on the character of a wine varies, based on several factors, including the type of wood used, the age of the barrel, the techniques used to make the barrel, barrel size, thickness of the staves (the individual strips of wood which form the barrel), cellar humidity and the length of aging. The factor on which winemakers disagree the most, however, is the type of wood used.

The type of wood the winemaker chooses is a question of tradition, wine variety, economics and personal taste. Due to its strength, resilience, workability and lack of undesirable flavor or color extractives, oak is most commonly used. Redwood, while commonly used in the construction of puncheons or uprights which are many times larger than the traditional 60-gallon oak barrel, is too rigid to allow bending of the staves and imparts an unpleasant flavor. Acacia imparts a yellow tint to the wine and is no longer common. Chestnut, although high in tannin (a by-product of the wood which in proper amounts improves the taste and allows a red wine to age by gobbling up oxygen which would otherwise spoil the wine) is too porous and must be coated with parafin to prevent excessive wine loss through evaporation.

Oak, on the other hand, has a relatively tight grain which permits a more gradual extraction of wood flavors and minimizes wine loss through evaporation. It also is resilient, enabling staves to be bent without braking, strong, durable, high in tannin and, unlike other hardwoods such as apple or cherry, has a neutral wood smell. As a result, oak is used almost exclusively in barrel aging of fine wines.

Coopers demand higher quality and pay higher prices for oak than furniture manufacturers. As a result, oak barrels are expensive. However, they are not necessarily appropriate for all grape varieties. The world's great wines from Bordeaux, Burgundy and California command a high-enough price and have sufficient aging potential to justify the expense of oak barrels. Less expensive wines and wines made with lighter, more delicate grape varieties such as white Zinfandel, Chenin blanc, Gewurztraminer, Riesling, some Sauvignon blanc and certain red grape varieties such as Gamay (Beaujolais) are bottled and intended to be consumed when still young and fruity. Aging these wines in oak would diminish their fruity appeal and would certainly not be justified in terms of cost. Instead, these wines are aged in stainless steel tanks under cool temperatures and for brief periods.

Among wineries which use oak, a difference of opinion exists between the majority who insist on French oak and the growing minority using American oak.

In the United States, white oak, grown in Virginia, Missouri, Kentucky, and Ohio, is the species used for barrels. White oak is preferred over red and black oak for several reasons, including tighter grain which minimizes evaporation of wine from the barrel; its resistance to shrinkage after wine is removed, an important feature in preventing wine from leaking out of a newly-filled barrel; and its high tannin content which benefits the wine and helps prevent decay of the barrel (tannin deters wood-boring insects and mold).

French white oak is harvested from several different forests in France. The most common forests are Limousin, Alliers, Vosges, Troncais and Nevers, each producing oak which imparts slightly different nuances of flavor and aroma to the wine. The tightness of the grain which determines the rate of extraction of these flavors and aromas, also varies among forests. Winemakers typically use a blend of barrels from different forests to take advantage of the unique characteristics of each.

This notion of regional character does not exist with American oak. Winemakers using American oak are more concerned with the reputation of the cooper than exactly which state the oak was grown in.

Beyond the variation among forests, the character of oak can vary among trees within a given forest due to factors such as growth conditions and age. The traditional 60-gallon oak barrel contains, approximately 31 staves from a variety of trees. A cooper's reputation is established on the basis of his ability to make a uniform product from year to year. While winemakers may welcome a degree of variation from vintage to vintage, consistency in the new barrels they purchase from one year to the next is critical.