Coming in various forms, barrels can play a crucial role in a wine’s conditioning, adding not only texture and body but also the widely cherished seasoning characters of vanilla, cedar and tobacco. They have been in use since at least the third millennium BC in ancient Egypt, where tubs with wooden staves were used during harvest. There is also evidence of barrels being used for storing wine in ancient Babylon, Iron Age Britain, Gaul and ancient Rome.
A barrel is constructed from several components: the head (the round ends which form the top and bottom of the barrel), staves (the shaped lengths of wood that form the sides of the barrel), and hoops (the metal parts that hold the staves together).
Not all barrels are created equal, however, with the origin of the oak trees that provide the wood being one of the key factors in determining the style of the finished wine. Other significant elements include the barrel’s dimensions, age and level of toast (see below).
The most common wooden vessel used in modern-day winemaking is the traditional oak barrel, usually made from either European or American oak. European oak is tighter-grained, resulting in firm but ‘polished’ tannins and more restrained flavours. They are considered to result in a finer outcome compared to their American counterparts, which are cheaper to produce and contain more vanillin compounds, therefore delivering more overt, sweeter characters such as coconut.
As to dimensions, the winemaker has at their disposal a smorgasbord of sizes whose capacities are often based on tradition: the Bordeaux barrique holds 225 litres, for example, while in Burgundy you’ll usually find 228L barrels.
Enormous vessels are an important part of Italy’s winemaking heritage, most notably in Piedmont where the Slavonian oak botte – generally holding anything from 1,500L-10,000L of wine – is woven into the region’s history.
In between these two extremes you will find puncheons or demi-muids, which hold 500L and 600L respectively. Even larger than that are French foudres, which compare with Italy’s botti.
Size is crucial as it determines the ratio of surface area in direct contact with the wine: the smaller the barrel, the higher the proportion of oak in contact with the wine, which results in stronger oak-derived aromas and flavours.
It is that surface area, the inside of the barrel, where toast comes into effect, with the level of toasting determining the flavours imparted into the wine. Taking place in the cooperage where the barrel is crafted, the barrel’s interior is charred with flames, which caramelises the sugars within the wood – the longer the exposure to flame, the higher the toast and the richer the flavours.
However, the flavour components released by this process into a wine diminish with time, which brings us to age. By the time the barrel has been used in four or five vintages there is little flavour left to give, though barrels will continue to be used, with winemakers keeping them as an option when in pursuit of a gentler touch of oak.