BEER AND WOOD
Part 2
Barrel-Raised, Fed Through a Spout.
Continuing the theme of the relationship between beer and wooden vessels, the next vital point is the ability of a wooden cask to allow the beer it contains to “breathe. Because wood is naturally porous, the beer has limited but continuous access to oxygen through the cask walls.
Many traditional brewers in Central Europe and the British Isles avoid oxygen as the devil avoids the holy cross. Apart from the yeast multiplication phase—when the wort needs sufficient oxygen to thrive—additional oxygen during fermentation, bottling, and storage is undesirable for almost all ales and lagers. Oxygen degrades the bitterness structure of the hops, gives the malt extractives a cardboard-like, stale taste, and turns the beer a dull grayish color.
The exception to this rule is the ever-clever Belgians, whose brewing tradition is so rich it includes seemingly archaic principles. Even their wort is “wrong” by modern standards for spontaneous fermentation: it is high in protein and starch, brewed with aged hops specially aerated to remove all aroma. Instead of being cooled as quickly as possible in a sterile environment, these beers are left overnight in large, open vats called coolships. Exposed to the night air, the wort is inhabited by the local yeast and bacterial “tribes” present in that moment. These are primarily genera such as Saccharomyces, Brettanomyces, and Lactobacillus.
While excess oxygen is undesirable for Saccharomyces after the initial stages, Brettanomyces requires a small amount of oxygen to develop its characteristic nuances—spicy clove notes, a touch of acetic acid, and a complex range of esters and phenols. The best way to ensure these microorganisms have the micro-oxygenation they need is through the walls of a wooden barrel. This is especially important since these ales often spend several years fermenting unhurriedly in wood before ever reaching a glass.
Consequently, the only branch of the brewing industry that did not abandon wooden barrels in the mid-19th century were the spontaneous fermenters on the banks of the Senne River, in the Lambic region outside Brussels.
Another factor that makes wooden casks ideal for this style of beer is that they can never be truly “sterilized.” Wood is porous, meaning its microbial inhabitants—a motley crew of different yeast strains—do not completely leave the barrel when the beer is emptied. A rearguard remains in the pores of the wood, patiently awaiting the arrival of the next sugary wort to begin the cycle anew.
If a cask begins to produce unpleasant flavors, it is dismantled, the inside is shaved down to a layer of fresh wood, and it is reassembled and re-fired. This is known as a reconstituted cask. Such a barrel provides fresh vanillin from the heat treatment, and the “rearguard” of previous occupants is wiped clean.
This is exactly the process undergone by our 2,000-liter wooden tank, which we acquired from an Italian cooper this spring. As our “Cask Number 13” was ready to start a new life, we paid special attention to the first wort introduced into the vessel. We were mindful of the cocktail of yeasts and bacteria that would lodge their rearguards in the pores of the wood for decades to come—indeed, a well-maintained wooden cask can last 100 years—forming the foundational flavor profile for every beer that will ever leave this tank.
A Detailed Description of the Loss of Innocence
To begin the life of our new vessel, we followed a specific ritual of inoculation:
– The Inoculation: We “seeded” the tank by blending one of our most promising batches—a two-year-old, spontaneously fermented beer from Eimuros—with our top-fermented Kilnbeer.
– The Wort: We brewed a fresh wort, rich in wild yeast delicacies – proteins and starches not converted into sugars – which we left to cool in a log in the open air for the local Eimur yeasts to inhabit. We did this during the growing month of Usiņi, traditionally considered to be the time when nature, including the yeasts, have woken up from hibernation.
– The Honey: We added raw, slightly “wild” organic honey from Latgale. Harvested slightly early, its lower sugar concentration allowed the sharp, floral “bite” of the wild meadow to shine through.
– The Juniper: We added juniper branches to the wort. In the Baltic region, juniper is more than a protector against evil spirits; it is a pillar of brewing history. Historically, juniper branches were used to store yeast between brews, acted as a natural filter bed during the mash, and served as a bittering herb.
In total, we have introduced yeasts from four different directions to our Kocene (wooden tank): Eimuru 2020, Eimuru 2024, Latgale honey, and the wild microflora of the juniper. We will discover the fruits of this labor at the end of the summer, when we might finally offer a few glasses from the Kocene to celebrate a new beginning.