Wine has been made in wood for hundreds of years. While woods like pine and chestnut have fallen out of favor, oak remains as the best and only choice.
Oak is easy to cut, yet very hard. It is good at holding liquids and helps clarify the wine by encouraging natural precipitation of sediment. Winemakers consider oak and the flavors it gives as a spice rack to flavor their wines.
There are two main types of oak that are used: The American White Oak (Quercus Alba) grows across the United States, although many feel that trees from the far north are too tannic, while oak from the south is too sappy. American Oak has a sweeter vanilla aroma, and it tends to work better with broader warm climate fruit. A barrel is generally in the $600 range, making it a less expensive option to European oak. Most barrels are sold to California, Oregon, South America and Rioja.
European Oak (Quercus Robur) can come from several different countries, including Slovakia, Russia or the Czech Republic, although France is the largest producer by far. Thanks to good land management, France has 40% of the EU forests, and about one third of these are planted to oak. These forests were planted about 300 years ago for ship building, as France needed to compete with the Spanish Armada and the Royal British Navy. There are seven reputable forests across the country, with Alliers, Nevers and Tronçais being the best. Individual trees are usually purchased in the 120 to 260 year range. European oak has a more taut and savory flavor than American oak, with barrels costing as much as $1500.
In the past, the most important thing when choosing a barrel was the forest was its origin. The wood from each forest had unique characteristics and identifying flavors specific to the region. Today, barrel technology has increased so much that choosing a Cooper (barrel-maker) is the most important. The oak is cut into staves, and a tighter grain is known to give more aromas with a slower evolution. A more open grain will give fewer aromas but more tannin. Most barrels are selected by grain rather than heritage.
Choosing a Cooper and the wood grain is just the beginning, as the wood will need to be dried and toasted. After an oaky 1990’s, the trend has been to have increasingly lighter oak and let the fruit shine through. This is achieved by leaving the cut staves outside for years. An environment with a lot of wind and rain will help leech out pronounced oak flavors after about 18 months. Coconut is also a flavor which can be desirable or not, and will disappear after 3 years. Flavors that are gained include clove and vanillin. The winemaker decides on which flavors they want (or want to stay away from) in the wine and order the appropriately aged wood.
The barrel is now ready for assembly. Staves are cooked with steam and bent to fit inside a couple metal hoops. Once one side of the barrel has been completed, a fire is lit inside and the wood is toasted. There are several levels of toasting, and more toasting generally means less oak flavor. Flavors developed during toasting are typically smoke, caramel and coffee. Once this process is finished, two metal hoops are fastened to close the barrel, and the construction is complete.
From the forest to the cooper, the barrel passes hands to the winemaker. New barrels give the most flavors, and are usually used for the heaviest reds, as they have the concentration to stand up to the strong oak flavor. This oak flavor diminishes with each use, with older barrels used for lighter, less expensive or secondary wines. Wine first out in a barrel will be toasty. In half a year , the wine reaches the 2nd layer of wood and will take on cinnamon and nutmeg aromas.
However, oak barrels do so much more than enhancing a wine’s flavor. They add richness to the texture, and make the wine more gentle and sophisticated. The oak also increase the rate at which sediment falls to the bottom. This t includes coloring agents which will make the wine more pale. It also removes sharp and astringent flavors, replacing them with a creamy mouthfeel. Older barrels give texture without flavor.
Sediment can harbor off-flavors and cloud the wine, so it is removed periodically in a process known as racking. Wine is siphoned into another barrel, leaving the sediment behind for disposal. Racking needs to be done about 2 or 3 times to result in a clear wine. Some producers rack several extra times to producer clearer wine with enhanced sweet vanilla flavor. Some wines are stored in a barrel for a couple months, while others for as much as 5 years. Fortified wines, such as Port and Madeira, can remain in barrels for up to 100 years!
As wood is porous, wine will evaporate over the course of time. This is known as the “angel’s share.” If the level of liquid in a barrel drops, the wine will be exposed to air and be ruined. To prevent oxidation, barrels are topped with the same or similar wine. About 5-10% of the wine’s total volume will be lost this way. The wine is also concentrated, giving it a longer shelf life.
One of the most shocking facts about barrels is that only 3-4% of wines are produced in them. Most white wines are produced and (minimally) aged in stainless steel which highlights pure fruit flavors. Many reds are simple wines consumed locally and need no adornment. As barrels are very expensive, alternatives have arisen. Staves can be removed from old barrels and resurfaced. They are then dangled in the tank to give oak flavor. Less expensive still are oak chips, or ‘sugar-cube’ sized blocks. The problem with these alternatives is that the oak will not fully integrate into the flavor of the wine, and always stick out. Chips taste like sawdust when young, and make the wine heavy and oily when aged.
As one can see, there are thousands of variations when it comes to how to oak your wine. Choices in forest, species, grain, drying, toasting, barrel age and barrel alternatives, all which affect the final flavor of the wine, need to be made. Well-judged oak can enhance and heighten an already great wine.