It is hard to argue with the idea that we are in the golden age of barrel aged beer. There are so many great breweries like Side Project, Toppling Goliath, Hill Farmstead and so many others putting just about every beer style in barrels of all kinds and the result is usually a great tasting beer. When there is a barrel aged beer that someone is particularly excited about, what seems to impress them the most is all the flavors that the beer offers when nothing has been added to the beer. So how do they get all those flavors in that beer? Why does it taste like coconut, vanilla and brownies when they didn't add any of those things? Barrels, much like hops malt, yeast and water, is another ingredient at the brewer’s disposal for making beer and here are some of the ways flavor is extracted from barrels and makes its way into the finished beer.
One of and if not the most important source of flavor that a barrel offers is the wood structure. There are parts of the oak structure and compounds within the oak that give us many of the flavors that we enjoy in barrel aged beer and they are lactones, lignins and hemicelluloses. The key to unlocking the flavor potential in each of these compounds is heat. When barrels are being produced at a cooperage, they usually undergo heat treatment. The two most common treatments being toasting, which is a low and slow process lasting anywhere from 20-40 minutes and charring which is a 10-60 second heat treatment to form a layer in the barrel and is often done in conjunction with toasting. The amount of time that a barrel is toasted and charred will determine what kinds of flavors the barrel will provide to its resident.
Barrel Room at Beachwood Blendery, Long Beach, CA
Alright, let’s look at those structural pieces of the wood and look at what they have to offer now that the barrel has received its heat treatment. Lignins are one of the building blocks of oak and if you have tried a barrel aged beer you have likely tasted the wonderful gift that lignins provide, vanillin. When lignins are subjected to mild heat or acid they can be converted into vanillin, which obviously gives a vanilla like flavor. As the amount of heat increases, the amount of potential vanillin in the finished product decreases and a heavier toast and/or char will bring about more smoky or medicinal flavors.
The next compound that makes up a good portion of the wood structure is hemicelluloses. These are made of simple sugars that, when subjected to heat, break down into their individual form and caramelize. This can give flavors of caramel, burnt sugar, almonds, baked bread and in some cases smoke or leather.
The last compound, lactones are contained within the wood structure and is the main source of that general herbaceousness that one can get from oak. And you guessed it, when subjected to heat, these flavors become more present, with it potentially expressing a rose like aroma or in higher concentrations bringing a coconut flavor to the forefront.
This is just a short list of ways that barrels offer some of the range of flavors that we all enjoy in finished beer. There are many other decisions a brewer can make to control how the beer will eventually turn out like storage temperature, amount of time spent in the barrel, size of, number of times and how long a barrel has held liquid, oxygenation and of course choosing the barrel in the first place and its previous contents. The world of barrel aging is vast, fascinating and we are all lucky that we have countless different beer styles to try that have been aged in barrels by some of our favorite distilleries that contain our favorite spirits like Pappy Van Winkle, Heaven Hill and Woodford Reserve. I hope this helps you enjoy your next bourbon barrel aged imperial stout just a bit more.