Paul Pontallier Bordeaux Wine Vinification, Wood or Steel

The Influence of Oak in the Maturing or Great Red Wine… Why Great Red Wine is Matured in Barrel

The technique of maturing great red wine in barrel was introduced at the beginning of the 18th century. The main principles have hardly changed, but the increase in knowledge has undoubtedly enabled it to be used to better advantage and to avoid cruel setbacks.
Nevertheless maturing in barrel is not an end in itself; strictly speaking it is not ‘ageing’. It is a phase in the life of the wine and its development, through which it acquires its capacity to age in bottle. The aim of maturing wine is, in fact. to favor and even to provoke a certain number of physical and chemical changes which arc indispensable to its ageing in the future. In the first place, the wine must acquire clarity and stability during its maturing stage. This point is fundamental for great red wines which are expected to keep perfectly for a long time (20, 30 years or more). This maturing must therefore create the conditions required for the various tartaric precipitations and those of the coloring matter which may be contained in the wine, so that they will not take place later on in bottle. Secondly, the maturing of red wine must lead to the stabilization of its color, as well as to a decrease in the astringency of the tannins. Lastly, during its maturing, great red wine must acquire an organoleptic complexity, which will allow the full development of the bouquet later in bottle.

Barrels made from cask oak, especially new barrels in the case of the greatest wines, provide a milieu very favorable to the evolution of all these transformations. To begin with, their small volume reduces the convection phenomenon which provokes a real drop in temperature in winter, and accelerates the precipitation of particles in colloidal solution. The barrel is thus a privileged milieu in which to obtain clarity and stability.
On the other hand, oak barrels ensure a slow and continuous oxygen penetration, estimated at 30-40 mg per year in new barrels. This leads to oxidation reactions, which, provoke a polymerization and condensation of the anthocyanin molecules and the tannins, which make lip the coloring matter in red wine. The following changes are the result of these chemical transformations:
-Increase in the coloring intensity.
-Evolution of the hue: the color of red wine takes on ruby nuances.
-Stabilization of color during ageing; the tannin/anthocyanin complexes formed during these reactions are more stable than the anthocyanin molecules which alone are responsible for the color in young
wine.
-Precipitation of the large tannin molecules (with various other elements), which in the long term guarantees the clarity of the wine.
-A decrease in astringency and hardness and the acquisition of ‘softness’, and smoothness, characteristic of red wine.
Furthermore there is the dissolution of certain elements in the wood which takes place during maturation in new oak barrels: first, the phenolic compounds, which exist in small quantity but are particularly reactive take part in the modification of the coloring matter of red wine; secondly, aromatic substances which contribute to the complexity or the bouquet of great wine. All of these elements that the wood imparts to the wine form, strictly speaking, ‘the taste of wood’. This follows a complex evolution: very pronounced in the first weeks after the new wine has been put into barrel, the taste of wood gradually blends into the wine as it matures in barrel and finally completely fades and becomes part of the bouquet of old wine. On putting into barrel, the ‘wood’ overtone often becomes severe; it is distinguishable on the nose alongside the fruit as a very pleasant vanilla aroma, which is sometimes a little green. The tannic impression is generally very strong on the palate; showing rather astringent tannins occasionally with a slight ‘dusty’ character. This initial ‘wood’ characteristic, disappears very rapidly, literally melting into the wine. After a few years of ageing in bottle, the wood can no longer be distinguished in the wine. The evolution of the aromas is astonishing and the bouquet develops and acquires superb complexity.

Therefore oak barrels add an important and complex contribution to the maturing of red wine. This cannot be limited to the fact that the wine acquires a certain ‘wood’ characteristic which should however be in balance with the other aromatic overtones and not dominant. I rests, above all, on the physical proper¬ties of the barrels and their aptitude to create an ideal milieu for the transformations that take place in the wine.

The Influence of the Origin of Various Oaks and the Techniques of Cooperage in the Success of Maturing in Barrel
Just as there are viticultural soils whose aptitude to produce wines of quality can vary very widely, so there are in a way ‘growths’ for oak, also of widely varying qualities. Here also France is very privileged. Numerous studies have shown the unequalled quality of its forests for the production of cask oak. With carefully chosen cask oak, coopers can put their ancient and ever mysterious art into practice. The drying, the shaping of the staves, the assembling of the barrels and the heating all make up the factors which will give each barrel its own personality. A work of art par excellence, each one is therefore the expression of the soil and the talent of the craftsman.

Influence of the oak’s Origin The coopers in the Bordeaux region use oak from two principal regions, the Limousin and the Centre of France (Allier). The Limousin oaks (essentially Quercus robur) grow on a soil of calcareous clay and granite covered in coppice-with-standard. Due to this the annual rings are large and regular; the structure is coarse; the porosity of the wood is high and the tannins represent 10% of the dry extract. The oaks from the Centre of France (Quercus sessilis being predominant) are on poorer silicious clay soil, which produces forests of full-grown trees, the most beautiful example of which is Tronçais. The annual rings arc narrow and the grain close, the porosity is not very high and the tannins represent about 6% of the dry extract.
There is very little significant analytical difference between two barrels of the same wine, one in oak from the Allier and the other from the Limousin. However, the organoleptic characteristics vary a great deal according to the origin of the wood. Experience shows that, in general, for red Bordeaux wines, oak from the Allier gives not only the most intense, but also the smoothest and the most pleasant ‘wood’ characteristic. In the case of Limousin oak, the woodiness is not only aromatically more discrete, but also sharper and bitter on the palate. Influence of the conditions under which, cask oak is dried. The mechanical resistance of the cask supposes that the level of humidity of the wood is in balance with that of the ambient milieu, about 14% to 18% in our temperate western regions. The use of oak in cooperage must therefore be preceded by ‘drying’ which can be obtained either by a natural or an artificial process. Natural drying is carried out in the open air over a period of at least three years. During this time not only does the drying itself take place but the wood is washed by the rain which leads to an overall reduction in the level of tannins. In addition a series of hydrolysis and oxidation reactions is provoked by the combined action of the enzymes in the wood and those secreted by micro-organisms which develop on the wood (ascomycetes, possibly)’ basidiomycetes and bacteria). These reactions lead to a condensation and polymerization of the tannins in the wood. Artificial drying is carried out by leaving the cask oaks for about a month in a ventilated drying room at between 40-60°C. This technique means that the drying time is considerably reduced without altering the mechanical qualities of the wood, but the above-mentioned reactions cannot take place.

The conditions under which cask oak is dried have a determining influence on the organoleptic characteristics of the wine in the barrels. Curiously, it seems that this influence varies according to the geographic origin of the oak. In the case of the Allier oak, only natural drying in the open air enables the wine to acquire the powerful ‘wood’ characteristic that is also fine, elegant and in harmony with the other organoleptic elements. When this oak is dried artificially, the ‘wood’ characteristic becomes aggressive, green, dusty and sometimes slightly resinous. This influence of the drying conditions seems less apparent in the case of Limousin oak. When this is dried naturally it gives the wine in the barrels a discrete olfactory ‘wood’ overtone, slightly bitter on the palate; in the case of artificial drying one finds the discrete aromatic woodiness, but the impression on the palate is often more pleasant and harmonious.

Influence of heat intensity during the curving of barrels: The curving of the staves is most frequently, carried out by using a fire. The heat from a fire of oak shavings gives them enough elasticity so they can be bent, thus giving the barrels their definitive shape. Sometimes, once the curving is finished, they are heated a second time, the degree of which varies a great deal depending on the copper. Each one jealously guards the ‘secret’ of his craft. A certain number of chemical transformations, notably the formation of aromatic aldehydes susceptible of modifying the composition of the wood, take place during this more or less intense heating, which sometimes amounts actually to burning the wood.
The degree of the char has a definite influence on the organoleptic characteristics of the wine in the barrels, to such an extent that more and more users are making specific requests for either a greater or lesser degree of char. In general the former gives the wine a more intense aromatic characteristic reminiscent of tobacco, smoke, sometimes even of tar, often to the detriment of finesse, of elegance and of the fruit. It is in fact a good example of the subjectivity of organoleptic analysis.
The origin of the oak, the conditions under which it is dried, the degree of heat and many other factors can therefore be very variable: as many different ‘tastes of wood’ as there are barrels; some more intense, some less so, some smooth, some vanilla flavored and some bitter. The technician is faced with a tempting choice, which makes it very difficult for him, because in a way it justifies his presence. But by choosing and therefore eliminating, docs not one run the risk of simplifying? In the same way our great wines arc the result of complex blends of grape varieties, soils, vines of different ages and perhaps the heterogeneity of the barrels also plays a part in the final richness of the bouquet.

Conclusion

Oak acts directly and indirectly, in a determining manner in the evolution of great red wine. But the wood in wine must be modest like the men who make wine and know how to hide behind the personality of that which it is there to help. Good wood does not make a great wine, it reveals itself. The wood plays a role in the process of evolution, but is not the end in itself nor the final result. Increasingly and especially among the new producer and/or consumer countries one associates the ‘taste of wood’ with quality in wine. But it is in fact the reverse. Wood only dominates mediocre wine. Its vocation is to disappear, to melt, to-be forgotten. It is the condiment which enriches the sauce without spoiling the taste. The man who has really managed to bring about the marriage of oak and “wine must work untiringly to render this union as harmonious as possible.

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