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USE OF OAK
The use of barrels is something which we take as being the norm. Enormously important in the process of winemaking, their use is due in part to happenstance. They just happen to be fitting vessels for transporting and storing liquids. Stone amphorae and animal skins had also been used but there were not many other possibilities prior to lined concrete tanks and stainless steel. Aside from their practical application, oak barrels also proved their worth in adding attractive flavour elements, texture and complexity, as well as allowing oxygen exchange.
Oak is extremely well-suited to barrel making. It is watertight, strong and yet malleable enough to be shaped. The flavour aspect results from the fact that oak interacts with the wines, impacting on taste and structure. Oak is a product influenced by both its cooperage and its environment. Soil, climate, annual weather and the construction method all influence the final product, in much the same way that these same elements influence a finished wine. It is this very variability which inspires, challenges – and sometimes confounds the winemaker. The best producers are, rightly, extremely particular about their barrels since they affect the taste of the finished wine. Used well, oak can improve structure and complexity in a wine, but if it is overdone hard-won nuances of flavour can be dwarfed by toasted notes and vanilla. Oak has to be respected as a form of seasoning and, as such, can enhance or spoil, depending on how it is used.
Four species of oak are used in winemaking Quercus Alba (American White Oak) Quercus Sessilifora, Quercus Robus (European Brown Oak) and, for cork, Quercus Suber. American oak has different characteristics from the European species, the latter being the more highly prized. Most valued of all is the tightly-grained French oak from the Nevers, Allier, Tronçais and Vosges forests. Having chosen the type of oak to be employed, the role of cooper is an important one. Every cooper will have their house style. Before making the barrels the oak must be seasoned in order to align the humidity of the oak with the humidity of its environment. This seasoning takes two to three years, during which time various positive chemical changes will take place. The process can be boosted artificially using ovens, but this does not allow for chemical evolution and tends to produce green, bitter notes in the finished wine. In addition to seasoning, the oak also needs to be heated, to allow the staves to be shaped. This toasting process also imparts flavour. The degree of toasting is just one more ingredient to add to the complexity and style of a wine and yet another element which a winemaker may employ harness to enhance his wine. Success relies heavily on the winemaker's knowledge, skill and experience if he or she is to create a balanced, harmonious whole from all the complex elements in both the wine and the oak.
A winemaker may choose either to ferment or mature his wine in oak, or sometimes both. Although barrels are watertight, they are air-permeable and the resulting slow, measured exposure to oxygen intensifies colour, softens tannins and allows for a gentle, natural stabilisation. Unsightly and unwanted particles, the lees, will steadily sink to the bottom of the barrel and the gradually clarifying wine can easily be racked off. Barrel-matured red wines are often racked several times and can sometimes be bottled without further need for clarification. For the rest, and especially for white wines, a fining agent will be used to render the wine star bright.
It should be noted that a labels which refers to oak, without mention of barrels, is generally an indication that oak flavour has been employed, by introducing oak chips or staves in the wine. Some worthy results can be achieved in this way but the subtle nuances, structural complexity and the seamless integration of fruit which results from time spent in a well-made oak barrel cannot be replicated.
OAK: THE OPTIONS
American or French: American oak is full, mellow and deep. Rich in tannin with prominent coconut, vanilla and bold spice flavours which some consider a little unsubtle. French oak is more subdued and takes longer to reveal its flavours and fully integrate with the wine.
Toast: Toast may be light, medium or heavy and the degree of toasting a barrel receives will affect the depth of flavour.
The proportion of new oak: New oak imparts the greatest intensity of flavour and the most wood tannin. 100% new oak or a high proportion of new oak should only be used for wines with structure and depth of fruit which will benefit from extended maturation. Too much new oak will dwarf subtle nuances in lighter wines.
Barrel size: Barrique (225ltr), Hogshead (300ltr) or Puncheon (475ltr) – the names are so much more poetic than small, medium or large, but the theory is the same – the smaller the barrel, the greater the oak to wine ratio, and the greater the oak's influence. Very large old oak barrels are used, for example, for maturing certain ports. Elements such as vanilla, toast and tannins have long-since dissipated and gradual oxygen exchange is the vessel’s prime purpose.
Time: Wine may spend anything from a couple of months to several years maturing in cask. Generally reds will mature for longer than whites although its not uncommon for sweet whites like Sauternes to spend up to three years in barrel. The tannins in the oak blend with the tannins in the wine; smoothing the structure, developing suppleness and texture, intensifying the flavours and acquiring complexity.