Since antiquity, a wide variety of woods from the tree species acacia, eucalyptus, chestnut, cherry, palm, pine and cedar have been used to make wine barrels. Wooden barrels were hardly known in ancient Greece, but the Greek historian Herodotus (482-425 B.C.) reports of such barrels made of palm wood in the city of Babylon. It is considered fairly certain that the Celts were already using wooden barrels for transport two to a thousand years before the era, and that the Romans took over this craft from them. However, the most suitable wood for wine storage or barrique ageing is oak. It is one of the hardest woods, is tough, very durable and yet easy to work. In addition, the nature of the ring-shaped pores prevents liquids from passing through the wood. This is ideal for building all kinds of vessels, especially barrels.
Last but not least, oak wood has a natural affinity to wine. The French recognized this very early and have been using it for centuries for the barrel type Barrique created in Bordeaux. There are about 300 oak species worldwide, but only three white oak species belonging to the taxonomic genus Quercus are used for the wooden barrels. Two of them grow in Europe. These are the winter oak, holm oak or sessile oak (Quercus sessiliflora or petraea), and the summer oak or pedunculate oak (Quercus robur or pedunculata). The third is the American white oak (Quercus alba) with numerous species. Generally, the American oak produces more astringent and aromatic wines than the European one. For the sake of completeness, we should also mention the oak species Quercus suber, from the bark of which the corks come.
For the oak barrels, wood from trees that are at least 80 to 100 years old is used. After completion, they are subjected to toasting (barrel firing). There are three groups of wood phenols that are added to the wine during the barrique ageing process. The primary ones are directly leached, the secondary ones are formed chemically and microbially from the wood phenols and the third group consists of those which are formed by the decomposition of the oak wood component lignin. The most important of these aromatic substances are eugenols, furfurale, lactones, tannins, terpenes and vanillins. Fine-pored woods release these substances slowly and in small quantities and coarse-pored woods release them quickly and in larger quantities. In French, for example, the grain is expressed as "grain fin" for a fine-pored wood and "grain gros" for a coarse-pored wood.
Until the beginning of the 20th century, oak wood came mainly from Poland, Latvia and Estonia. Today the wood comes mainly from France and North America. The American oaks of the Quercus alba species grow mainly in the dry forests of eastern North America. The most important producing countries are Arkansas, Iowa, Minnesota, Missouri, Oregon, Pennsylvania and Wisconsin. The wood has a distinct, perfumed aroma. It is particularly suitable for red wines with a strong taste made from Cabernet Sauvignon, Syrah or Tempranillo (Rioja). In addition to the country of origin, it is often grown in Australia and in Europe, especially in Spain. Increasingly, oak trees from Croatia (Slavonia), Romania, Russia, Belarus, Ukraine and Hungary are also being used. Small quantities also come from Austria (Manhartsberg and Ybbstal in Lower Austria) and Germany.
The type of wood preparation in barrel making plays a very important role. Optimum barrel stave boards should be produced in such a way that the annual rings are at right angles to the wine side and the medullary rays are parallel to them (the medullary rays lead from the core in a star shape outwards to the bark). If the medullary rays are aligned differently, the wine can diffuse (evaporate) to the outside. This is not taken into account in the production of construction timber, where the so-called gang cutting is used in order to have as little waste as possible. An alternative in barrel building is splitting the trunk along the medullary rays. This makes the wood less permeable to gas, which results in a lower sulphur dioxide input.
However, this advantage is partly lost again by planing. Since splitting is more cost-intensive due to the amount of work and the large loss of wood, the so-called star cut (also mirror cut) is often used, which is carried out along the medullary rays. When drying the staves, the water content of the staves is reduced from 45% to 15%. In order to be able to shape the staves accordingly, the half-bound barrel is heated over an open fire at a heat of approx. 200 °Celsius. This results in a browning and in extreme cases in a distinct charring or roasting, the desired toasting for barrique maturation.
Worldwide, French oak is considered the best due to its fine aromas and is most commonly used in Europe. The areas of origin are not too humid and the soils do not contain iron. The two European oak species relevant for barrel making occupy an area of over four million hectares (40,000 km²). This makes France by far the largest European supplier of oak wood. Every year, the Tonnelleries produce around 200,000 barrique barrels here. The most common designations listed below refer to the origin. However, as there is no AOP(Appellation d'Origine Protégée) for oak wood, it is not possible to derive the exact origin from the name under which the wood is marketed. In addition, there is oak wood from the two regions of Jura and Burgundy, as well as from the Argonne Forest near Champagne. A speciality are barrels bound from woods of different origins (wood mix).
Allier: Département in central France named after the river of the same name (a tributary of the Loire) The Saint-Pourçain appellation is also located here. The Nièvre department, also important for oak wood, borders to the north. The particularly fine-pored Allier oak is considered the highest quality oak. The tannins, which are rather less present, have a pronounced, sweet taste of vanilla. Dreuille, Gros Bois and Tronçais are considered to be the best forest forests (see also below). In addition to the general name Allier, the woods are also marketed under the name of these forests. By far the most commonly used oak wood is equally suitable for red and white wines.
Bois du Centre: General term (Engl. "wood from the centre") for oak wood from central France, which can refer to products from different départements.
Cher: The wood is named after the département of the same name in central France, the forests are around the capital Bourges. To the south is the department of Alliers. The fine-grained wood is less tannic than that of Allier, so it produces milder wines.
Limousin: The name of this oak wood is derived from the region (landscape) of the same name in central France to the west of the Massif Central. It covers the départements of Corrèze, Creuse and Haute-Vienne. The extensive woodland area adjoins the département of Allier to the southwest. The soils containing granite, clay and limestone provide a large-pored wood with fewer aromas, whose rich tannins are released very quickly. This results in highly astringent wines. It is mainly used for wine spirits such as Armagnac and Cognac, and to a lesser extent for powerful red wines from, for example, Cabernet Sauvignon, Grenache Noir(Garnacha Tinta), Syrah and Zinfandel.
Nièvre/Nevers: The wood is named after the Département Nièvre or its capital Nevers, which is situated on the Loire. The department of Allier borders to the south. Here is also the appellation Pouilly-Fumé. One of the most famous forests is called Bertranges. The oak wood is also often used for the barrel type Pièce. It has medium-fine pores which release the tannin relatively slowly. The wood is soft and sweet, but slightly more tannic than Allier, beside which it is one of the best. It is used especially for wines made from Cabernet Sauvignon, Carignan Noir(Mazuelo), Grenache Noir, Sauvignon Blanc and Syrah.
Tronçais: The wood comes from the forest of the same name in the north of the Allier département. It is particularly fine-pored and rich in tannins and is particularly suitable for red wines from Pinot Noir (Blue Burgundy) and white wines from the Chardonnay and Pinot Gris (Grey Burgundy) grape varieties.
Vosges: The wood comes from the département of the same name in the region of Lorraine in the north-east of France on the western foothills of the Vosges. The very light-coloured, almost white wood has fine pores and is rich in tannins. Due to the large differences in altitude, however, there are slightly different types of wood. It is particularly suitable for white wines from the Chardonnay and Sauvignon Blanc varieties.
As an alternative to the relatively expensive and time-consuming barrique maturing process, wood chips (pieces of oak wood) and staves (oak battens) as well as special containers under the brand names rebarriQue and Stakvat have been used in the New World for a long time during vinification and/or aromatic essences have also been added to the wine. Within the EU, such techniques have so far only been partially permitted on an experimental basis by way of derogation. The trade agreement between the EU and the USA, signed at the end of 2005, resulted in a liberalisation (see under Wine Act). Within the EU, the addition to wine of oenological tannins (in solid form) and, since 2007, the use of wood chips is permitted. See also under Barrel and barrel.
Oak tree: from RegalShave on Pixabay
Allier River: by Jean-Pol GRANDMONT - Own work, CC BY 3.0, Link
Allier map: from Boerkevitz, CC BY-SA 3.0, Link
Barrique cellar: by MPW57 - Own work, in the public domain, Link