Wine and French oak generally imparts less strident flavours than American, though American reated in the same way as French (air dried rather than kiln dried; split rather than sawn) can be reasonably subtle, and the handling of American oak has improved. (French oak barrels are also approximately twice the price of their American equivalents.) Oak from Minnesota and Wisconsin is much used, though some winemakers find it too tannic; Oregon oak is now beginning to be used, though only on a small scale so far.

French oak, wine

French oak may come from a variety of different regions: Limousin oak is wide-grained and tannic and often used for brandy; Tronçais, Allier and Nevers is tight-grained and much used for wine; Vosges, too, is tight-grained. Oak from Slavonia in Croatia has long been popular with Italian producers, who favour it for their large old casks. German oak, which can give a spicy note, may also be used, and Russian and Hungarian oaks are making a reappearance.

Wine may be stored in a variety of materials, including stainless steel, concrete, fibreglass and wood. (Wood usually, but not always, means oak; in Savennières in the Loire, for example, chestnut and acacia are traditional. Italy also uses some chestnut. Austria and Croatia use some acacia.)

In most of these, except in wood, the wine, if it is kept at a low temperature and not allowed to oxidize, will not change or develop, and will retain its youth and freshness. Indeed, one Sauternes estate, Château Gilette, keeps its wine in concrete vats for up to a couple of decades before bottling it. At bottling the wine tastes almost as young as it did when first made.

But aging in oak barrels is different. First, there is a small exchange of gases through the pores of the oak; this slow oxygenation softens the astringency of the young wine and reduces the fresh primary aromas. Old oak barrels, which impart no flavour of their own to wine, are sometimes used to achieve this.

New oak barrels also give certain flavours to wine, most obviously vanillin. This has a delicious affinity with the flavour of some grapes, notably Cabernet Sauvignon and Chardonnay, and these are often aged in small new oak barrels (usually 225-litre barriques, often known as barriques Bordelais simply because they are the size traditionally used in Bordeaux) for maximum oak flavour. If overused, however, new oak can dominate the flavour of the wine and make all wines taste alike.
But it is not just the oak that imparts different characters to the wine: the choice of cooper is equally important. Winemakers experiment with different coopers, and settle on those most suited to their wines, just as much as with different oaks.

And then there is the question of toast. All barrels are bent into shape over a fire, and the fire inevitably toasts the inside of the barrel. Barrels given a heavy toast impart a spicy, toasty, roasted coffee flavour to wines, but give less oak flavour because the toast acts as a barrier between wine and wood tannins. Barrels with a medium toast will create wine with more tannin and vanilla; barrels with a light toast will impart more tannin again.

Obviously, the smaller the barrel used the greater the effect of the wood on the final wine. The most common size is the 225-litre Bordeaux barrique but this is beginning to lose popularity in favour of the 500-litre barrel as consumer tastes move away from profoundly oaky wines. The Burgundy pièce is slightly bigger, at 228 litres, and while most regions have their speciality sizes, few producers in Chablis still use the traditional feuillette of 132 litres.

Traditional German barrels are the Mosel’s 1000-litre Fuder and the Rhine’s larger 1200-litre Stück. Italian botti come in various sizes, as do the pipes for aging port in Portugal. In Australia hogsheads are commonly 300 litres, but nobody is bound by tradition these days and winemakers choose their barrel sizes according to the effect they want the wood to have on their wine style.

New oak barriques have another effect as well: they help to fix the colour of red wines, and polymerize the tannins. (In other words the molecular chains of the tannins are lengthened so that the tannins taste softer.) The sooner the wine goes into barrique, the better: the malolactic fermentation is often done in barrique for this reason. Oak chips or oak staves have the same effect of fixing colour and polymerizing tannins; in addition, if chips are added during racking they reduce the necessity of adding sulphur dioxide, since they actively protect the wine against oxidation.

They also give a touch of oak flavour, but they can’t imitate the oxidative effects of proper barrel aging. Oak chips are generally illegal in Europe for appellation contrôlée wines or the equivalent – which is not the same thing as saying they are not used.