Whiskies have several centuries of history that includes their storage in wooden oak barrels. Until a few years ago, beer was also aged and stored in wooden oak barrels. Tabasco hot sauce, balsamic vinegar, and other types of specialty foods were often aged and stored in wooden oak barrels. Observers may wonder about the specialty of wooden oak barrels and the reason oak is selected.
All wood is not appropriate for food storage, especially when liquids are being stored in the barrel. For centuries, coopers have preferred hardwoods, especially oak for use in creating these wooden barrels. Wooden oak barrels have remained the most popular and exclusive choice for use in creating whisky, wine or beer barrels.
A cooper is a person who makes barrels. The location where the wooden oak barrels are coopered is the cooperage. The cooper is a trained artisan who hand cuts and shapes the wooden staves that are held together with metal rings to create a vessel that is a bulging cylinder. A fire is maintained in the cooperage to provide the heat needed to bend the wooden staves into the shape needed for the barrel. The cooper will add the precise number of metal rings over the staves to ensure the staves remain in place. Becoming a respected cooper takes years of training and practice. Most learn the trade by serving a long apprenticeship under a respected cooper.
Coopering quality barrels requires the cooper to obtain the best oak, cut and shape the staves and then fire them to bend correctly while also giving them the desirable slight charring. Oak slowly leaches phenols that contain tannins to mix with the spirit stored in the barrel to add character and flavor to the drink.
Coopers prefer either French or American oak to flavor wine. Wooden oak barrel from French oak provide a more subtle flavor than those from American oak. Whiskey distillers use different types of oak according to the geographic location and type of spirit. For example, in the US, the law requires straight whiskies be aged for two years in new White Oak barrels. The law also specifies that Bourbon be aged in charred new White Oak barrels.
Drinkers may wonder about the significance of wooden oak barrels. For a Chardonnay drinker the use of barrel aging and fermentation results in wines with flavors that come from the mix of the tannins in the wood to produce flavors of caramel, vanilla and toffee. By balancing the time the spirit is in the barrel, surface area of wine contact with the wood and many other factors, the winemaker is able to produce wines that have a wide range of tastes and dryness.
For a connoisseur of red wines, tannins in oak provide a magical way to help the reds to evolve. Charring of the wooden oak barrel brings out aromas and flavors of spices such as cinnamon or clove, pencil lead, cedar, cream and mocha.
Fluctuations in humidity and temperature as the whiskey or wine ages in the wooden oak barrels allow the oak to infuse the flavor. During these times of expansion and contraction, part of the alcohol, known as the Angel’s share evaporate to concentrate the flavor even more. This helps to improve the character and dimension of the liquid inside and requires the distiller or wine maker take precautions to balance these effects on the finished product.
The full influence of wooden oak barrels on a spirit are only realized during the first three uses. Therefore, winemakers use both old and new barrels. While certain spirits require the manufacturer to use new wooden oak barrels, due to the requirements of the law above, others do not. As distillers must have new oak barrels every year, there is a global demand for more of the wood. Since oak and other hardwoods grow slowly it is easy for the demand to outweigh the available material. Harvesters must take precautions to replant and manage natural resources in order to ensure the supply for the beer, wine and whiskey industries remains sufficient.