Roll Out The Barrel
When you’re talking about bourbon, the discussion usually starts with grain. It’s got to be 51% corn, that’s the big rule you’ll hear first. After that you can have a combination of grains including rye, malted barley, and wheat. And of course, it has to be made in ‘Murica! You’ll also learn that it has to be aged in new, charred oak. A fact that doesn’t sound all that interesting; I can’t remember the last time I was at a party and struck up a conversation about cooperage (challenge accepted!). But once you start leaning into the science of aging whiskey, you’ll find that it’s one of the most fascinating aspects of bourbon production.
Almost all of the American white oak for Kentucky bourbon is grown in the Ozarks. One tree typically yields two 53 gallon barrels (the industry standard size for most distilleries), and the trees are typically harvested at around 100 years of maturity. That’s pretty crazy right? Now think about the fact that there are more bourbon barrels aging in Kentucky than there are residents of the state. That is a metric heck ton of trees ya’ll. (And you better believe they’re planting just as fast as they can.)
What makes the wood so important? American oak has hundreds of flavor compounds, and as those interact with the distillate over time, the liquid absorbs those qualities. Vanilla, caramel, cinnamon, allspice, coconut -- none of those flavors come from the distilled grains themselves, these are all a gift from the wood.
To access those flavors, you must first char the barrel. That involves a very hot flame that essentially cooks the inside of the barrel, caramelizing the sugars from the sap. The most intense form of char that many distilleries use to accomplish that “classic” bourbon profile is called Alligator char (No. 4.) Imparting color as well as flavor, this is where your white dog officially becomes bourbon. Now you can see why the type of wood used is so important, and why using it is mandatory for the spirit to be labeled as bourbon.
And then we go down the rabbit hole. What about other kinds of wood? How do they affect the spirit they interact with? Where do we start? Probably with French oak, the next most commonly used wood in barrel making. But Limosin or Monzelum black oak? Then we have native woods such as Mizunara in Japan, Garryana (a type of white oak) in Oregon, Chestnut in Germany, Amburana in Brazil. Each has its own specific flavor profile, and those profiles can be changed based on how much you char or toast the wood. It’s not just the salt and pepper, it’s the dry rub and the sauce. What comes off the whiskey still is raw, savory and sweet, and not at all unpleasant. But it is immature, and lacking in depth. In the life cycle of whiskey, this “new make” is the caterpillar, and what emerges from barrel is the butterfly.