Today, in many regions, the properties of new oak barrels are used for red wine and, to a lesser extent, for white wines such as Chardonnay. A wine that’s aged in oak gains spicy and toasted or grilled flavours.
Since the 1970s, when oaky flavours in wine started to become fashionable, ageing wine in new oak barrels became widespread. But it’s not just for the oaky flavours that a winemaker may decide to age wine in a barrel.
The word barrel is used generically to describe all wooden barrels. However, barrels come in different sizes. The most well-known barrels are the Bordeaux, which holds 225 litres, and the Burgandy, which holds 228 litres.
Over time and through a process of trial and error, the ideal size for a barrel was determined (an average capacity of between 200 and 230 litres became accepted) and the Bordeaux barrel became the standard.
New oak barrels provide the wine with the most aroma and flavour. When used for the first time, there is an exchange of elements back and forth between the wood and the wine. The wood imparts tannins and other substances to the wine and the wine deposits tartar crystals and a portion of the wine into the wood. Over years of use, the tartar crystals build-up which causes the wood to have less effect on the wine.
Older barrels do not impart tannins but instead offer slow oxygenation which helps to soften the tannins and blend the flavours of the wine.
Oak has proved a popular material in which to age wine because of its physical properties and its flavour contribution.
Oak contains 18 different phenols (aromatic organic compounds), which impart flavours to the wine such as vanilla, coconut, pepper, smoke, etc. Oak also provides the wine with tannins, known as noble tannins, which are different from the tannins transmitted by the skin and stalks of the grapes, which are known as vegetable tannins. The tannins provided by the oak help strengthen the structure of the wine.
Winemakers carefully consider the source of the oak for their barrels.
Oak from the Limousin forest in France is strong and firm with a coarse grain and powerful tannins, making it well suited to brandy.
Other oaks, such as the Sessile, have a finer grain which produces softer tannins and is more suited for maturing wines such as Barolo.
The demand for oak in the wine industry is high and it takes around 180 years for an oak tree to mature sufficiently before being used to make barrels.
French oak is no longer sufficient to meet the ever-increasing demand so the coopers, who make the barrels, now source their oak from countries such as Poland, Russia, and Slovenia. American oak is also used but is not so suitable for wines that need a long period of ageing.