Production and aging of wine in the small oak cooperage

Wines & Vines, March, 2001 by Richard H. Graff, Andre Tchelistcheff

The U.S. wine industry today is confronted with perhaps its greatest challenge since the lifting of the pall of prohibition. The people of the country are at last awakening to the "pleasures of wine," and there is developing a larger and larger group of discriminating wine consumers. The doubling in ten years of table wine consumption in the U.S. is only one indication of a dramatic trend, but this increased is marred by the fact that the consumption of foreign table wine has increased at a much faster rate than that of our own table wine. Our wine industry, if it is to maintain or better its position in the domestic and world markets, must respond effectively to the rapidly increasing and as yet unsatisfied demand for wines of high quality.

It is particularly appropriate at the present time, therefore, to examine one of the extremely important factors in quality wine production: the use of small cooperage.

As there is a dearth of information on this subject, especially in the English language, we feel it important not only to present our own findings, but to amplify them with material gathered from prominent French sources. Our procedure has been to examine the French methods as regards the use of small cooperage, specifically in the Burgundy and Bordeaux regions, and to apply them in California--both in a small winery (Chalone) and a comparatively large one (Beaulieu).

In France we visited the forests in which the trees for cooperage wood are grown; the fendeurs who split the oak into the stavewood or merrains, the coopers, and the winemakers. In California we used and tested the methods and procedures described in the sections entitled Treatments and Winemaking Techniques and confirmed through practical experience the observations and conclusions presented in the sections entitled Mechanisms, Economic Aspects and Quality Control.

Materials; Manufacturing Processes

The classical quality classification of oak [1] based on sensory evaluation of wines produced in barrels made from different types of oak is as follows: First quality: French oak, Second quality: Austrian oak, Third: Russian oak, Fourth: American oak. It has been observed [1] that freshly-cut French and Austrian oak give off a slight perfume of vanilla, whereas freshly-cut American oak has a rather harsh and disagreeable odor. This classification and observation are not well documented, however, as to the effects of treatment, aging and exact source of the wood. Some further experimentation is certainly indicated using American oak in the classical process of cooperage manufacture, although there are indications that much of its heavy oakiness remains and can impart an objectionable flavor to wines and brandies.

Outside of oak, other woods important in the cooperage industry are Chestnut and Locust. The former is considerably cheaper than oak, but is very porous, with an evaporation loss twice that of oak. For this reason it must generally be sized on the interior. Locust (or false acacia) is very tough and resilient with a very limited porosity. Its evaporation loss is only about half that of oak. It produces extremely stout barrels which are excellent for the shipping of wine. It is not generally recommended for the aging of fine wines, however, as its effect on the wine is almost negligible. It is commonly used for Muscadet and the wines of Anjou.

Oak Species. Of the nearly 500 species in the genus Quercus, there are three principally employed for cooperage, vis. Q. robur and Q. pedunculata, in Europe; and Q. alba in the United States.

In France the two species, Q. robur and Q. pedunculata, are generally found together in the forests and there are countless hybrids. The number and extent of the hybrids is ever increasing due to the practice of using random sprouts from the forests for replanting. Only in such forests as that of Troncais has any effort been made to maintain a single species (Q. robur). In general, however, Q. pedunculata tends to prefer the moist, deep soils of the valleys and plains, while Q. robur is more common in the hills and mountains and generally requires less moisture.

French Oak Characteristics. Although it was attempted at first to relate the different regional characteristics to species differences, it soon became apparent, after visiting a great many forests, that the regional characteristics of French oak are determined principally by soil and climate, the two main species being pretty well mixed and hybridized.

1. Limousin Oak--named after the former province of Limousin--comes principally from the department of Haute-Vienne near the city of Limoges. The region is rough and hilly, the soil granitic, saliceous and sandy, with a complete absence of lime and iron. The perfume of this oak is said to derive from the soil. Q. robur tends to predominate, and both the trees and the forests themselves are quite small and widely scattered. The toughness and very course grain of the wood results from the poor growing conditions, which tend to restrict vertical growth in favor of lateral expansion. The trees are thus stocky and tortuous, and the irregular grain renders the wood more difficult to work satisfactorily by high-speed machines. The forests of Rochechouart and Brigueuil are typical examples.