Oak

Why oak matters

Oak contributes four things to a wine. It adds flavour compounds, including vanillin (vanilla), lactones (coconut and spice), eugenol (clove) and various phenolics. It allows a slow, controlled micro-oxygenation, which softens tannins and stabilises colour. It contributes tannins of its own, which build structure. And it provides a physical vessel that can be reused for several years.

The choice of oak, the toast level, the age of the barrel and the time the wine spends in it all shape the final result. A new French oak barrique adds more oak character than a three-year-old barrel. A medium toast adds more spice than a light toast. American oak adds more vanilla and coconut than French oak. These choices, taken together, are a major part of a winemaker's signature.

French vs American oak

French oak, from forests such as Allier, Tronçais, Vosges and Limousin, is the most popular choice for premium English wines. It is tight-grained, low in harsh tannins and contributes a refined, complex flavour. American oak, mostly from the Appalachians, is wider-grained and more aromatic, with stronger vanilla and coconut notes. Many winemakers prefer the subtlety of French oak, but American oak has its fans.

Hungarian and Slavonian oak sit in between, with their own character. Slavonian oak, in particular, is favoured for large old casks that are used to age wines without adding much oak flavour. For the English market, where the dominant style is a delicate Chardonnay or Pinot Noir, French oak is the most common choice.

Barrel sizes and shapes

The standard Bordeaux barrique is 225 litres. The standard Burgundy pièce is 228 litres. Both are used in the UK. A larger 500-litre puncheon is becoming more popular because it gives a gentler oak signature and works well for Chardonnay that is intended to spend a long time on lees. Smaller barrels, like the 114-litre Burgundy roll fermage, give a more intense oak character per litre of wine.

The choice of size is a stylistic decision. A premium still Chardonnay from a top English producer might spend 9 to 12 months in a mix of new and used 500-litre puncheons, getting complexity without the heavy oak signature of a barrique programme. A prestige cuvée might be entirely in new barriques, with the oak doing more of the talking.

Oak in the UK industry

All major English producers use oak. The main cooperages supplying the UK include Seguin Moreau, Taransaud, François Frères, Tonnellerie de l'Adour and Damy. A new French oak barrique costs around 800 to 1,200 pounds, and the UK industry spends several million pounds a year on barrels.

The industry has become more sophisticated in recent years. Forest of origin matters: oak from Tronçais tends to give more structure, while Allier oak is finer and more aromatic. Toast level matters: most English producers use light to medium toast, with a few trying heavier toasts for specific cuvées. And the age of the barrel matters: producers typically use a mix of new, one-year-old and older barrels to balance oak and fruit.

Alternatives to oak

Oak alternatives, including oak chips, staves and stainless steel barrels with oak inserts, exist and are used in some UK wineries. They are cheaper and faster than real barrels, and they can add oak character without the investment. The critics argue that they give a more one-dimensional oak flavour. The defenders argue that they allow oak character in wines that are sold at lower prices, where a full barrique programme would be uneconomic.

For premium wines, real oak remains the standard. For entry-level wines, oak alternatives are a viable compromise. The label does not have to specify which was used, but most premium UK producers are happy to declare their full oak programme on the technical sheet and the website.