Definition: Oak (origins of the wood)

Three species of oak provide most of the wood used in cooperage. In Europe, these are sessile oak and pedunculate oak (Quercus petraea and Quercus robur). In North America, they are white oak (Quercus alba and related species). Oak contains two main types of polyphenols: ellagitannins, which are water-soluble polyphenols and constitute the bulk of the extractables from oak wood; and lignins, which are insoluble polymers of a polyphenolic nature. Grain: coopers refer to two standard oaks to define the types of grain: Limousin oak with a wide growth (4 mm and above), coarse or loose structure and high porosity for coarse grain Allier oak (the archetype of the vintage being Tronçais) with fine growth (close to 1 mm), fine or tight structure and low porosity for fine grain (Pontallier 1981). Pedunculate oak is a pioneer and heliophilous species that finds its ecological optimum in all situations outside high forests (coppices, hedges and open fields) where it grows rapidly, as in Limousin, which is the benchmark for coarse grain in cooperage. In contrast, sessile oak tolerates high forests much better, where it grows slowly, as in the Tronçais forest. Its higher lactone content gives it a more powerful and complex aroma with notes of coconut and fresh wood. A: Troançais and Jupille; B: Allier and Vosges (the latter is recommended for Chardonnay) as well as oaks from the forests of the centre, in the Châteauroux region of Indre; C: Nevers (particularly the Bertrange forest). Oak is very well suited to Pinot Noir.

The wood preferred by winemakers for the production of barrels for ageing and maturing wines, particularly for the great red wines of Bordeaux, Piedmont, California and other noble regions, and for the great white grape varieties. Oak contains a whole range of polyphenols (substances that give rise to aromas), the most important of which is vanillin (responsible for the vanilla aromas that are easily detected in young wines that have been aged in new oak). The tannins provided by oak combine with those from the stems and skins, sometimes adding extra astringency. There is a whole alchemy surrounding barrels: depending on the origin of the wood, the thickness of the staves and the intensity of the toasting, the barrel will impart more or less tannins and aromas to the wine. The great French forests that produce the best wood are those of Berry and Limousin, the latter region where oak grows more quickly, providing more aromatic phenols.