The Celts are considered to be the inventors of the wooden barrel made of staves (= longitudinal timbers). Long before there were stainless steel or plastic containers, wooden barrels were the preferred transport and storage containers for all kinds of liquids. Often it was wine, but water, rum, oil or beer were also transported from one place to another.
In the past, pitch was used in breweries to seal the barrels. It was heated, poured into the barrel and spread as thinly as possible by turning. This layer was tasteless and also served to protect the beer from wood aromas. The process is called pichen and is only practiced by a few breweries today.
Today
At present, wooden barrels have one main purpose: to add flavor to beer. Spurred on by the craft beer movement in the USA, many breweries in Europe also began to mature their specialty liquid creations in barrels. There are basically three types of barrels and their influence on the aroma of the beer: Firstly, new, untreated barrels can be used. These mainly release the flavor of the wood and tannins used. Secondly, there is the option of toasting new barrels. In this process, the cooper heats the inside, which breaks down the tannins that are perceived as astringent.
Depending on the strength and duration of the heat exposure, the wood develops a different flavor profile. Oak, for example, can produce notes of vanilla, coconut, caramel or spices. The third and probably most common method is the use of used barrels, as the aromas from the pre-seasoning are desirable. Whisky or rum barrels are particularly popular. However, there are no limits to creativity; beers made from Calvados, cognac, wine or tequila barrels are also available.
During storage
Handling wooden barrels is not easy for breweries in the initial phase. You have to leave the comfort zone, especially in the microbiological area, because a wooden barrel cannot be cleaned like a stainless steel tank, as the wood has a microflora that contributes significantly to the flavor profile of the stored beers. In addition, a wooden barrel will never be completely airtight. However, the resulting oxidation is desirable.
It promotes notes of honey, dried fruit, sherry or port wine in the beer and increases with the length of storage. This ranges from a few months to years and depends on the taste you want to achieve. The contents of the barrel are therefore regularly tasted. Most breweries fill the wooden barrels twice. After that, they are "exhausted", but sometimes they are returned to a distillery, which in turn benefits from the beer's aroma.
Beers for the barrel
Due to the strong aromas that come with wooden barrel ageing, most breweries tend to prefer heavy, high-alcohol beers for this, such as a Doppelbock, an Imperial Stout or a Barley Wine. Depending on the beer style and type of barrel, there are countless possible combinations. In some places, the rule of thumb is that nothing below 10 percent alcohol by volume is put into the barrel, because the higher the alcohol content, the better the protection against unwanted microorganisms.
Characteristics and shelf life
Barrel aged beers are not comparable to a lager or pilsner. They are not thirst quenchers, but a complex aromatic pleasure. They are most enjoyable when drunk from a long-stemmed, wide glass at room temperature. They are excellent accompaniments to food, can hold their own with hearty dishes or can even ensnare a dessert. However, many beer fans prefer to drink a wooden cask beer just like that, after a meal.
You could say they are ideal when the fire is crackling in the fireplace. One interesting aspect is the shelf life of these creations. If you have the patience and allow the bottle to mature in a cool, dark place for a few more months or years, you will often be rewarded with a drink that has gained even more complexity.
