Not long after the emergence of metal kegs in the sixties, wooden casks vanished from commercial packaging almost completely. Some microbrewers still employ them in the making of cask ales in the UK and other parts of the world, but that’s it. Whilst the beers filled into wooden barrels for transport and serving have a very short shelf life, the gas-sealing metal kegs can keep their contents fresh even for several years. Not only that, but these are easier to handle, to transport, to work with in general. Nevertheless, wooden barrels are becoming a more and more common sight in craft breweries, but in a different application.
It's 2022, and the majority of breweries employ closed-system fermentation, just like the wineries making reductive wines. This modern approach to clean fermentation has numerous advantages over the old-school way of fermenting in open top vessels, and wooden fermenters. Think about the ease of cleaning and sterilization, and also the fact that it is possible to ferment under pressure, which is good for the yeast, and thus the beer. Modern styles, like NEIPAs, couldn't be brewed without these advancements on a reliable, commercial scale. This, however, doesn’t mean that techniques from the past can’t be employed in this new age of brewing. In fact, for certain styles there is no other approach.
During the barrel aging process we are working with a previously finished beer that is stable. At this point I would like to highlight that Fehér Nyúl’s facilities are close to brand new, and our products - for the most part – are not stabilized beyond waiting for the fermentation to completely finish in the tank. Our beers are unfiltered, and unpasteurized. The fermented beer, rich in carbon-dioxide and alcohol, is introduced to a wooden barrel, usually around 200 liters in capacity. Due to the fact that wooden barrels don’t hold pressure, the CO2 escapes quickly, and as pressure equalizes, air from the surrounding room is let into the vessel. The speed of this process is determined by factors such as ambient temperature, moisture in the air and also pressure. In the case of spirits, where the aging process can last decades, these factors change based on the seasons’ weather. The change in temperature also changes the volume of the liquid inside the barrel. The expanding spirit can move into the wood’s pores, leaching out flavor compounds in the process. Usually, the harshest compounds are the first to be extracted, but over time, with the help of oxidations, these flavors and aromas develop into more harmonious, mellow counterparts.
In the case of our beers though, we are looking at shorter aging times, usually between six months to a year. This is primarily because the barrels we use have already been used to fully age, or finish a spirit or wine. These used barrels are mature in a sense that most of the harsh compounds – tannic acid for example – had converted into the mellow molecules responsible for the flavor of the drink that was previously aged in the vessel. Of course, there are still important compounds left inside the wood that are responsible for vanilla, caramel and spicy notes in the aged beer.
Then there is the spirit or wine that was aged in the particular barrel beforehand. Residual liquid inside the wood’s pores mixes easily with the beer, so there is no need for a multi-year, or even decade-long maturation process. In general, what we are waiting for is the mixing of flavor compounds arriving from the wood, the spirit and the base beer. Once the concentration of these flavor-, and aroma molecules are sufficient, we arrive at a point that the brewer and blender is looking for. The peak, after which further aging would tilt the balance, and potentially ruin a perfect beer.
To put it simply, this is the artistic side of brewing. Modern brewers have a previously unimaginable amount of control over the developing beverage, which is only going to improve with new scientific discoveries. We understand the majority of fine details regarding mashing, sparing, boiling, cooling, fermentation and packaging. And yet, when a brewer decides to barrel age his precisely planned and fine-tuned beer into a wooden barrel, said person gives up his immense control, and lets nature take its course.