Although barrels were initially only intended to be a container for wine, it is general knowledge that the wood character thus imparted adds another dimension to wine.

It is also true, however, that the wood character of a wine is not necessarily complementary, but might even be excessive or unbalanced. The source of the wood character will certainly also play a role. If a wine is matured in a barrel of recognised quality, it will differ markedly from the same wine to which alternative wood products had been added. In a similar way the maturation circumstances such as temperature and humidity will also important roles. The question arises therefore, exactly how positive is the role played by wood in the vinification process

The English Institute of Wine Masters conducted a seminar on oak in 2005 in conjunction with the wine department at Christie’s and the Taransaud cooperage. Five tastings were held of different 2004 French and American wines that had been matured, inter alia, in specially made 30 litre oak barrels with different variables, to evaluate the influence of the variables.

Fermentation in stainless steel, new or used barrels

Ramey Wine Cellars of Carneros, California, compared the influence of Chardonnay fermentation and maturation in new and used oak barrels as opposed to stainless steel containers. In addition they also investigated the influence of lees maturation and battonage. Their results may be summarised as follows:

The wine matured in stainless steel has the least flavour with delicate grapefruit and grassy flavours. Wine matured in the second fill was most reminiscent of a Burgundy style accentuated especially by its milky cheesy flavours and soft taste. The new barrels obviously imparted a marked wood character on the nose and taste and on the latter in particular it was the most complex of all the treatments.

French, Polish and American oak

Chateau Malartic Lagraviere of Bordeaux, France compared the influence of French, American and Polish oak barrels to the vinification of Sauvignon blanc in stainless steel. Wood maturation took place extramurally in medium toasted barrels for 24 months. The results of that investigation may be summarised as follows:

The wine made in stainless steel was thin with little colour and had a coarse lemon and lime character. The grassy character of the wine resulted in an unpleasant aftertaste.
French oak maturation resulted in an integrated wine where the floral notes were complemented by the buttery oak character.
American oak resulted in overwhelming cucumber flavours and although the taste was also smooth, the prominent caramel and baked spice flavours confirmed the origin of the oak.
An unbalanced character was noticeable as regards the Polish barrels. Although caramel and spice flavours also occurred, the uniqueness of the oak, described by some of the tasters as cardamom, did not find favour.
The same cellar did the same comparison using red wine, but the tannins made the differences less obvious. The difference between the French and Polish wood in particular was more difficult to notice, but once again the aggression and cucumber flavours of the American oak were dominant.

Troncais, Vosges and Central French oak

Oak used for barrels may hail from Northern, Eastern or Central France. Oak from the cold eastern and northern parts usually belongs to the Quercus sessilis species and imparts more complexity to wines compared to the central Alliers and Troncais oak that result in a more spicy character and a better mouthfeel respectively in wines. Southern central Limousin oak imparts a more aggressive vanillin character to the wine.

Corton Charlemagne Grand Cru wine was matured extramurally in medium toasted barrels for 24 months and again compared to wine stored in stainless steel. Although the barrels from the cooler northern regions imparted more structure to the wine and the southern regions’ barrels showed more prominent oak, the tasting results were not consistent and nuances were the only difference among the wines.

Influence of air drying

If wood is not sufficiently dried, the green tannins of the wood can be observed in the resultant wines. It is not only the period of drying that plays an important role, but also the means of drying. It is therefore recommended that when buying cheaper barrels, made of wood that had been dried for a shorter period, a heavier toasting should rather be specified seeing that the green tannins will then be less noticeable in the wines. The drying of the wood is necessary to stabilise the wood before it is used for barrels. The moisture content of the freshly split wood therefore has to be reduced from 55 to 15%. The best quality barrels are made of wood that has been air dried for up to 4 years.

Red wine from Chateau Lagune and Sauvignon blanc from Chateau Malartic Lagraviere, also mentioned above, were matured in barrels made of wood that had been air dried for 24, 12 and 6 months respectively. In both instances the barrels that underwent drying for 6 months contributed least to the wines, those that underwent 12 months’ drying showed the most tannin and wood character and the 24 months’ drying resulted in the most complex wines with the best mouthfeel.

Toasting level

The toasting of wood develops flavours that are more or less noticeable sensorially depending on the intensity and duration of the toasting. The toasting levels may range from light or medium-minus, medium, medium-plus and heavy to intensive. Light toasting is for example at 120 – 180C, medium toasting at 200C and heavy toasting at 225C.

A Sauvignon blanc/Semillon blend from Domaine de Chevalier and a Merlot from Chateau d’Aiguilhe both in Bordeaux were exposed to no, medium and heavy toasting compared to a stainless steel control. In both instances the heavily toasted barrels produced the most complex wines. The red wines showed no difference in colour, but the white wines were increasingly yellow with increased toasting. Untoasted wood produced a coarse, short taste in the wine. Although vanilla, caramel and clove flavours were noticeable in the medium toasted samples, heavy toasting resulted in the most prominent flavours and taste characteristics, as could be expected.

In the light of the different influences that the above factors have on the character of wine, winemakers and cellars will always differ about their preference for a specific wood character in their wines (Canterbury, 2006).

Reference:

Canterbury, C. 2006. Oak’s Influence on Making and Maturing Wine. Wine Business Monthly December 2005: 34 – 37.

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