European or American oak barrels?

The choice between European and American oak barrels is a pivotal decision in winemaking, profoundly influencing the aromatic and taste profile of the wine. This distinction stems not just from the barrels serving as vessels for wine storage but as integral tools in the wine's maturation process. Oak barrels facilitate the wine's evolution through oxygen ingress and their role in the transformation of polyphenols, alongside imparting specific aromatic and flavor compounds to the wine during the aging phase.

Although various wood types have been or are used for barrel-making, such as chestnut, acacia, mulberry, ash, cherry, beech, birch, poplar, elm, pine, fir, and others, oak wood is the material of choice for constructing wine barrels today. Only certain species of oak are deemed most suitable for this purpose, highlighting two or three species of European oak and several American oak species.

The type of oak used in barrel construction and its cultivation location, alongside the wood drying techniques and the intensity of heat applied during the construction process, are significant factors in how the barrel interacts with the wine it holds.

Most cooperages today source oak wood from controlled forestry operations, where a meticulous cultivation and selection process of trees includes primarily two phases: the growth phase, from seed rooting until the trees reach about 100 years old, achieving a diameter of around 25 cm and a height of 10 to 12 meters, and the exploitation phase, yielding about 70 to 100 trees per hectare, reaching heights of 30 to 40 meters at 120 to 160 years old, when they are felled.

For barrel construction, only the heartwood or duramen, the central part of the trunk, is used.

The American and European Oaks

The genus Quercus, with over 600 species, falls under the Fagaceae family in the Quercoideae subfamily. Its cultivation spans the Northern Hemisphere, extending south to Central America and Ecuador. Out of these, only about fifteen species are utilized in cooperage for the storage of alcoholic beverages, owing to their liquid-tight properties.

European Oaks

In Europe, oak species are widely mixed and grouped into four subgenera: Quercus, Oersted, Erythrobalanus, Cerris, and Sclerophyllodrys. The most commonly used European oaks in barrel making are Quercus petraea (or sessilis), found in central France in areas like Allier, Argonne, Burgundy, Center, Nièvre, and Vosges. This species thrives in poorer, sandy soils and requires less light, resulting in trees that are taller, thinner, and have a finer grain and lower polyphenol content.

Another significant European oak is Quercus robur, grown in the fertile soils of France's Limousin region, requiring abundant sunlight. This results in shorter, broader trees, producing a more porous wood with a coarser grain and higher polyphenol content.

France is the leading producer of European oak, with about three million hectares of oak forests managed by the Office National des Forêts (ONF), although significant quantities are also found in Eastern Europe, like in the former Yugoslavia, Hungary, Russia, etc., with Quercus frainetto being notable for its similarity to Petraea.

American Oaks

In America, particularly in the United States, a vast array of oak species are cultivated, divided mainly into two subgenera: Quercus (white oak) and Erythrobalanus (red oak). Red oaks are primarily found in the eastern United States, overlapping with white oaks, and in Canada. North America is known for its production of red oak, Quercus rubra, which, due to its high porosity and lower resistance, is not used in barrel making. However, white oaks, which are less porous, are utilized in cooperage, particularly Quercus alba, known for its excellent properties.

In the U.S., oak wood is often referred to by its geographic origin rather than its botanical name, hence terms like 'Missouri oak', 'Ohio oak', and so forth are common.

Differences Between American and European Oak

While both oak types are suitable for winemaking, they offer distinct differences that can significantly affect the intended wine style, both in terms of physical qualities and the compounds they transfer to the wine.

American oak tends to be denser, offering greater strength and rigidity, ideal for storage and transportation. In contrast, European oak provides higher permeability and porosity, facilitating better micro-oxygenation and wine evolution.

In terms of tannins, American oak contributes predominantly gallic tannins, which are less 'sweet' and more astringent. European oaks, on the other hand, impart ellagic tannins, which are sweeter and result in a smoother astringency.

Additionally, American oaks are characterized by slower drying but boast high durability, whereas European oaks dry quicker and also have high durability, each bringing their unique influence to the wines they age.