Wood and winemaking

Spice, smoke, vanilla, coconut... wood can be a game-changer for a wine. Producers who use it face myriad decisions: specific type, place of origin, size of vessel, toasting level – all key to what you smell and taste

- NANCY GILCHRIST MW

Wood and winemaking. It might sound prosaic; after all, wine has been made in wood for centuries. What could be more quotidian? But scratch just below the surface and a world of alchemy and wonder awaits.

Mostly, wood for wine is made into barrels. These practical vessels are resilient, easy to repair, transportable and more or less water (wine?)tight. They also come in many shapes and sizes, which is important because when it comes to wood and wine, size really does matter.

Wood is semi-porous, meaning that air can permeate through it, and the vaporous elements of wine in the other direction. In a small barrel, the wine-to-surface ratio is relatively high, so the oxidative impact will be greater than in a tonneau of 900 litres or more. Here, the process of micro-oxygenation slows to a sedate, sometimes almost imperceptible pace. Ellagitannins (oak tannins) help to limit the formation of sulphur compounds during fermentation and protect the wine from oxidation. Fruit flavours appear purified, mineral characteristics are polished, malolactic conversion is encouraged, and any tannins polymerise into a fine mesh of integrated elegance that gives the wine true ageing potential.

But if size matters, so too does the type of wood. Traditionally, winemakers would use what was close to hand. Chestnut, cherry and acacia were – and still are – used to a limited extent, but it is the mighty oak that reigns supreme.

ALL ABOUT OAK

Of the hundreds of species of oak (‘Quercus’), only three are used regularly for wine. Quercus robur (known as common oak, pedunculate oak, European oak, English oak or, particularly in the wine world, French oak); Quercus petraea (sessile oak or eastern European oak – found in Hungary, Poland, Slovenia, Croatia and elsewhere); and