Off the vine: The role barrels play in aging of wine
By Gino L. Filippi
It has been written that if grapegrowing and fermentation are analogous to the birth of a wine, barrel-aging can be likened to its formal education. Wine is not made by formula, but by following preferences of taste and flavor.
Today we examine more closely oak barrels and their influence on finer wine production. Exactly who constructed the first barrel is not known, but the history of barrel-making is interwoven with the history of wine.
The practice of storing and transporting wine in wooden casks made its appearance in Europe in first century B.C. in the territories of the Celts and the Illyrians. In 92 A.D., in an early example of protectionism, the emperor Domitien decided to destroy the Gallic vineyards which had become a major force in wine production. Around the same time Pline the Elder noted the appearance, in the regions near the Alps, of an exceptional vessel specially conceived to hold wine: the wooden barrel. It was used in the colder countries, while elsewhere wine was stored in earthenware vases.
Why are white oak barrels used so extensively today? Because white oak is indispensable to the conservation and aging of fine wine, carbon dioxide and volatile ethers that cloak the aroma of the wine evaporate through the wood. Evaporation occurs because the barrel is similar to a filter, allowing water and alcohol to diffuse through the wood. Thus, the remaining wine becomes slightly more concentrated in flavor and character. A real transformation of the wine occurs. Slow oxidation, allowed by the porosity of the wood, helps the wine lose its astringency and harshness, giving way to softness and suppleness instead. Generally speaking, red wines take on a warmer color and lose their purple-blueness.
Around the 1950s, American winegrowers discovered French barrels. Afterwards, all wine-producing countries looked to improving the quality of their wine by keeping it in French oak.
Today, white oak barrels of French, American, Hungarian and other origins are commonly used throughout wineries worldwide. Each wood type offers a different flavor profile to the wine (more on this issue in a future article).
Utilizing wood to age wine is complicated as it must communicate a good taste, without allowing oozing; it must be resistant, but have a certain suppleness to allow the working (bending) of the wood while communicating some of its tannins. It is white oak that best fulfills these conditions.
Chestnut wood has all the necessary qualities but is too rich in tannin, bringing much harshness to the wine. It is also too porous and the evaporation is twice that of oak.
There are 400 identified botanical species of oak. The predominant species:
– Quercus robur or q. pedunculata. Other designations for this oak include English oak, robur oak and pedunculate oak. The Forest of Tronais is typically robur, but there are hybrids. The wood is of excellent quality; tender and fine-grained. This species prefers hills or even mountains and accounts for 14 percent of the total surface area in forestry.
– Quercus sessiliflora or q. petraea, also commonly known as sessile oak. The wood is also excellent quality, especially for the main trunk (the stave-wood.) This represents 19 percent of the total surface area in forestry. The local terrain and climate also determine the characteristics of the wood. All of the following regions in France provide oak for barrels, although three regions are best known: Argonne, Allier & Tronais (considered as the same forest), Bourgogne (Burgundy), Cantal, Cher, Nivre Creuse, Corrze, Gers, Haute Vienne, Indre, Limousin, Loir-et-Cher, (Nevers), Prigord, Puy de Dme, Rhne et Vosges.
What barrel for what wine?
The grape variety must be taken into account, and the nature of the vintage. When in contact with the wood, wine undergoes many changes. The choice of wine for aging must be taken into account because it is not the barrel that will determine the final quality of the wine. The aroma of the wine develops first and becomes more complex upon contact with the wood.
The wood yields many of its inherent substances to the wine, or substances that are formed during the heating of the barrels when manufactured. There then follows a range of transformations and slow, controlled oxidation thanks to the porosity of the wood. Then, in moderate quantities, the wood yields its extractable and aromatic components.
Louis Pasteur, at the request of Napoleon III in 1863, was the first to study the phenomenon of oxidation-reduction. He had been instructed to find the reasons for wine spoilage. He found that wine, even when carefully protected from contact with air, would absorb oxygen and this can happen through the staves but in particular during racking. He gave the example of a barrel in the Clos de Vougeot which would produce a younger tasting wine than other barrels because it had been painted. His conclusion was that excessive contact with the air allowed vinegar-producing bacteria to flourish. On the other hand he found that very slight amounts of oxygen helped maturation of the wine even during several years after bottling due to dissolved oxygen in the wine.
The structure of the wood has more impact than its geographical origin. The coarse grain gives a coarser and more “rustic” character with a touch of bitterness at the end of the taste analysis; the evolution of the phenolic compounds in a wine during the first few months of ageing is accompanied by a progressive reduction of the free anthocyanidins and virtual stacking of tannins to create larger, complex, heavy structures.
“A wine which is rich in these large tannin strings will respond well to the new oak at the beginning of maturation. A well-matured wine must focus on its own intrinsic characteristics.
Fine grain gives woodiness faster than coarse-grained wood. The fine grain is often preferable after some months of aging, then one notices that the coarse grain is preferable for the same geographical origin, the lowest appreciation is caused by excess woodiness which is accompanied by slight bitterness and dryness in the finish.
Fine grain is more appreciated for white wines. In red wines, the natural polyphenol composition means the effect of the grain has less importance.
New wines need a tannin support – useful for the first finings – this is why new casks are normally used.
“Bordeaux” barrels have a capacity of 225 liters min. (60 gal), “Burgundy” barrels 228 litres (60.8 gal), a “Mâconnais” 212 litres (56.5 gal).
Each different region has its barrel shapes and capacities which constitute a brand of origin and authenticity. When the metric system was adopted in France, there were efforts to apply the reform to barrel-making, giving fixed, uniform shapes and dimensions.
“La Chauffe” (heating): the barrel must be put back over the burner to reheat it. This second heating allows evaporation of the moisture used in wetting, but most importantly, to seal the fibers of the wood to avoid movement and breakage of the staves. Winemakers demand different degrees of toasting (the caramelization of the wood rather than charring) depending on their aims and experience.
Toasting may be light, medium or heavy. Certain winemakers request for the barrelheads only to be charred.
There is one issue that all winemakers unanimously agree, a sound cellar and barrel maintenance/sterilization program (more on this subject coming soon) is essential in maintaining a bacteria free environment.
Enjoy a glass of wine tonight!
Gino L. Filippi can be reached at Ginoffvine@aol.com