The wooden barrel, which succeeded the amphora, dates back to 350 BC. It was probably the Celts who were the first to develop and use these containers (almost exclusively used for wine) with rounded, watertight shapes that facilitated the transport, storage, sale and vinification of wine. It was in the 17th and 18th centuries that techniques of barrel vinification (maturation and ageing) began to be developed, particularly in Bordeaux where the wine was then sent to England in barrels and on lees.
In the 20th century, other materials replaced wood, such as concrete, fibreglass and stainless steel, for storing, conserving and transporting liquids. However, the use of barrels (barriques or foudre) was maintained both for vinification (in the case of certain white wines) and for the maturing of certain wines. Moreover, in the 1980s, the trend towards maturing in wooden barrels returned; the American wine critic Robert Parker probably had something to do with this, promoting wines with woody aromas resulting from maturing in oak barrels (tertiary aromas of spice, toast and vanilla).
The barrel is not only a means of storage but also a tool for wine making. It has a direct influence on the aromas and structure of the wines (the contribution of tannins for example) due to the molecules such as phenols, vanillin, aldehydes and lactones contained in the oak. The use of new barrels further amplifies this phenomenon. The size of the container is also a determining factor in the degree of these interactions. The larger the barrel, the less concentrated its molecules are and therefore the less virtues it will bring to the wine.
A wine matured in a 225L barrel will carry much more of the aromas from its maturation than a wine matured in a 500L barrel.
The wooden container allows a little air to pass through, mainly through the bung hole which allows it to be filled and causes very slow and limited oxidation of the wine. This softens the tannins (in the case of red wines), complexifies the aromas and sometimes enhances the colour. The “angels’ share” (small quantity of wine that evaporates) is also due to the exchange of air, so it is necessary to regularly fill the barrel to the brim, to proceed with topping up, if one does not want the wine to oxidise (except in the case of oxidative wines, such as certain Jura wines). Wood also helps the natural clarification and stabilisation of wines.
Nevertheless, maturing a wine in a barrel is expensive (the price of a 225l French oak barrel is between 600 and 650 €) and requires more handling than with other containers. It is therefore preferable to use it for “value wines” to give them that final effort of complexity and strength.
Care should also be taken, as although wood is intended to blend in and enrich the wine like a condiment with concentrated wines that already have structure, it may overwhelm certain small, too light wines with its aromas and tannins and may supplant those of the grape.
The virtues of barrel aging
During the aging process, tertiary aromas, mainly brought by the wood of the barrel in which the wine is aged, are revealed. The main tertiary aromas that appear thanks to the wood are :
The work of the Cooper
1 – The selection of the wood :
This is a fundamental step in the manufacture of a barrel. The wood is the raw material and will condition the quality of the barrel and the wine making process (aroma contribution, softening of the wine…). To make the barrels, we use oak wood, which is renowned for its nobility and the fineness of its grain. The oak must be at least 120 years old and have a diameter of 50cm. In France, the Sessile Oak is preferred for its aromatic qualities and its more discreet tannins.
Once the selection has been made, the logs (raw wood) must be cut into staves (wooden planks).
2- Drying the wood
Three years of rest in the open air (exposed to sun, rain and wind to dry naturally) are necessary for the staves to remove bitterness and astringency while refining the aromas and tone of the wood.
3 – Manufacturing
The staves are then shaped by hand to create the staves that form the body of the barrel. The wood is then softened by heating and moistening it, then the staves are bent and assembled with iron hoops. The cooper therefore assembles the barrels without nails or glue and holds them together only with the metal hoops.
4 – Heating or bousing
This stage consists of “burning” the inside of the cask in a more or less intense way. This allows the characters and aromas that the wood will transmit to the liquid to be modulated. Then comes the moment to insert the bottoms of the barrel, to pierce the bung and to check the tightness of the barrel. Finally the barrel is ready and will be signed (with a laser).