Fermentation takes place in large concrete-lined underground chambers, in tile-walled cellars, in stainless-steel vats and in wooden barrels of various sizes. All the vessels used are basically neutral in that they add nothing to the wine itself. All, that is, except wooden barrels.

Many types of barrels are used, such as acacia, redwood, pine, and chestnut, but it is oak which is the choice of most quality winemakers. Most used are barrels made of either American or French oak and the world-wide preference is for French oak, the export of which has brought generated large sums of money for the country's coopers (barrel makers).

Although a quarter of France is forested, there is a definite preference for oak from the forests of Vosges, Allier, Troncais and Bertranges, while the ideal wood is between 80 and 100 years old. It's then seasoned, either by being left out and weathered for a couple of years or by being dried in a steam kiln. How the wood is seasoned and for how long makes a difference to the quality of the barrels. The barrels are made by bending wooden planks over small fires, held by hoops and then beaten into shape. The extent to which the inside of the barrels are charred by this possess also influences the taste of the wine.

But, exactly what difference does the oak make to the wine? Oak brings its own flavour to the maturing wine, can change its colour and also adds tannins. Also, wine resting in oak barrels allows more contact with the air than the more inert materials mentioned above. A little air contact seems to work in the wine's favour, too much, however, and the wine could be ruined, so the amount is all important.

If the barrel is new, it will have a high quantity of tannins and oak flavour to add to the wine. But if it is used each year with a new wine, it soon losses these qualities, so there is a constant demand for new oak barrels. Size is also of great importance as a large barrel will have a lower ratio of surface area to volume, therefore the oak qualities will not be so pronounced. If you want a very oaky wine, then smaller barrels will obviously be preferable.

The important thing is balance. If a wine is made which has a good balance of fruit, acidity, and oak, then the winemaker has done a good job. If the acidity, tannins or oak are too predominant, then the wine is "out of balance". In some cases, this can change through time and improvements can occur, but by no means always. Some wine is fuller of flavour and can take more oak than a lighter bodied wine.

So, next time you raise a glass, can you detect the oak? Has the wine been oaked at all? Can you detect a slight vanilla or buttery flavour, a slight hint of sweetness? Can you detect whether the barrel was well burned? Is there a suggestion of toasting in the wine flavour? Think about it.