Roaster’s Notebook: How does barrel-aged coffee work?

I am not a scientist.

That’s probably obvious if we’ve ever met. But for those of you of whom I haven’t yet had the pleasure, I want you to know, right here up front, I am not a scientist.

In fact, when I’m not roasting coffee, I’m usually either teaching marketing or writing novels, so whatever the exact opposite of being a scientist is, I’m pretty close to that.

I lead with this just to set expectations. I’m about to describe to you my understanding of a rather scientific process, and in case any actual scientists read this, I don’t want you to find me on Twitter and @ me about coffee bean chemistry or the molecular properties of gin-soaked American oak. I’m on a journey of understanding, and what I’m about to type is my understanding of the barrel-aged coffee process at this point in that journey.

Please don’t @ me. I don’t like confrontation.

So! Onto the post about our barrel-aged coffee, and the magic—er, science, I guess?—that makes it happen.

I absolutely love when we bring Bootlegger out to sample at farmers’ markets. Almost no one can resist the mystery of a barrel-aged coffee, and almost everyone who tries it takes a literal step backward and says something like, “Whoa! You can really taste the whiskey!”

I love seeing that reaction. It fills a very specific joy-chamber in my heart. I’m proud of each and every one of the coffees I roast at Reconstruction, and they’ve all been met with extremely positive reviews, for which I’m so grateful…but the success of the Bootlegger series feels like a unique sort of victory.

When you roast a specialty coffee, you start off with a general idea of the flavor profiles you can expect. Different coffees from different regions tend to adhere to typical flavors (Want something chocolately? Go with the Guatemala! Looking for lemon? Try the Tanzania!). My job as a roaster is to try to unlock those flavors in a way that makes the coffee special, approachable, delicious, and very, very drinkable. But I have a guide to go by. I have a general sense of what I’m looking for, and all I need to do is dial it in.

But when we dropped our first batch of green coffee beans into that original Pinckney Bend American whiskey barrel…I had no idea what to expect. I didn’t have a roadmap for the flavors that would come out of it. I didn’t know if the barrel would have much impact at all.

I just filled it with beans, rolled it every day, and hoped against hope that we’d end up with something worth selling.

But I understood the general science behind it, and I had high hopes. Green coffee beans are extremely porous. Put them under a microscope, and they’re absolutely riddled with holes. In a good and natural way, not in a weird and defective way. They’re the perfect specimens for soaking up liquid and storing it deep within their bean-y little selves.

Which is what makes the prospect of aging them in whiskey barrels—or gin barrels, or wine barrels, or any barrels that have been soaked through with alcohol—so enticing. When we rest our beans in our barrels, we’re literally letting them soak in the whiskey residue that’s left in the wood after the barrel is emptied. You may not know this, but wood is also really porous, so when you put liquid into a barrel, it sort of flows in and out of the wood. That’s how whiskey and barrel-aged wines get that oaky flavor; the liquid goes into the wood and pulls out some of that woody goodness. And in that exchange, some of the liquid gets left behind too, so the wood of the barrel actually gets that good whiskey flavor.

If you broke apart a barrel and gnawed on it for a while, you’d probably get a pretty good buzz going.*

So here’s the timeline: Whiskey gets poured into the barrel. Whiskey seeps into the pores of the barrel. Whiskey is removed from the barrel, leaving behind trace amounts of whiskey in the barrel. Coffee beans get poured into the barrel. Some of the trace amounts of whiskey from the barrel seeps into the porous coffee beans. The beans soak up the whiskey. The whiskey beans are dropped from the barrel and roasted.

Because there’s only a trace amount of alcohol in the beans, and because that alcohol starts to evaporate at 172 degrees, the intoxicants burn off in the roasting process (I roast our barrel-aged coffees to temperatures just shy of 400 degrees). But the flavors are left behind, and the aromas are left behind, and what we get is a coffee that smells and tastes not unlike an Irish coffee! Add a splash of cream to it, and your taste buds might honestly not know the difference.

Voila! Bootlegger.

We’re currently working with small 15-gallon barrels from our generous friends at Pinckney Bend, and each barrel nets us between 25 and 35 bags of Bootlegger. Each batch tastes just a little different, because we’re always playing around with different beans. The Brazil seems to hold the flavor best, but the Guatemala gives it a slightly richer note; we haven’t tried the Ethopia in there yet, but we’re pretty excited about the possibilities!

Each batch rests in the barrel for two weeks before we drop it and roast it, and the barrels have to be turned daily, to mix the beans around and make sure all of them spend some good quality time with the whiskey-soaked wood. Crafting Bootlegger is a labor of love that takes time and patience and care (the beans roast differently than “typical” coffee beans, since they have a higher moisture content! It’s…a whole thing). That’s why it’s a special release, and only made available in limited quantities.

Our next batch of Bootlegger will be ready before long! The very complex science of past demand says it’s likely to sell out...why don’t you game the system by pre-ordering your bag now?



*almost certainly not scientifically accurate


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