If you think about it, wood is pretty miraculous stuff. Just take a moment to ponder all the wonderful things you can do with it. It provides shelter in the form of homes. It can be whittled into a snazzy phone case. If you have enough wood, it could be dug out into a canoe so that you can paddle downstream, get lost and therefore have to use your phone that is well protected by its wooden case. Hell, you could probably make trees from the stuff ... maybe I have that one backwards.
Personally my favorite use for wood is for making barrels. Despite what your hippy-dippy neighbor has told you, barrels are meant for alcohol -- not for collecting rain water or for planting patchouli. As a whiskey distiller, I’m usually found neck-deep in barrel, which to most people sounds like an enviable position. Those people would be correct. (You may now take a moment to join in their envy.)
Barrels can theoretically be made out of a variety of woods, and on occasion I will chance by one coopered oddity or another, but there is good reason why oak has been the wood of choice for whiskey production for so long. For whiskey production American oak is most often the wood of choice. The wine guys love their French and Hungarian varieties and those wood types certainly have their place, but the effects and flavors are different. So what’s the deal here? Why oak and more specifically, why American oak?
For people who really love Latin and sounding “science-y” the American oak is of the genus and species Quercus alba. It grows well throughout the Eastern U.S. from Missouri to the coast and from northern Florida (aka NoFlo for people who are too busy for actual words) to southern Canada (aka SoCan). Historically its ubiquity in this part of the country played an important role: being so common, it was a natural choice for coopers to transform into barrels.
But there’s more to the story than that. Oak and particularly in our case, American oak, maintains all the qualities that coopers and distillers require. It is very strong and durable, yet with the proper tools can be relatively easy to shape. Also, unlike so many other tree types, oak has no resins that would otherwise contribute negative flavors and aromas.
So essentially we have a wood that can be easily shaped into barrels and does NOT smell like grandpa’s couch cushion after Thanksgiving dinner. That’s great for your neighbor’s rainwater, but for booze it’s about as interesting as listening to Lindsay Lohan’s thoughts on anything requiring more than a bean sprout’s IQ. There’s still one more important ingredient for a great whiskey barrel: fire. For American oak to really work its mojo on the whiskey, we need to char the inside of the barrel.
Charring is a process where the cooper burns the inside surface of the barrel with direct fire for a period of time. Obviously the longer the flame contact, the more burnt or charred the inside. No one is really sure exactly how the process of charring barrels came about and numerous origin stories abound. However I have a favorite and therefore “correct” version of events so be sure to bust this little ditty out at your next whiskey tasting.
Once upon a time in the backwoods far far away, a distiller was about to fill some barrels after a long day of stickin’ it to the taxman, but he realized said barrels had last been used to take some fish to market. So he flamed the inside of the barrel to hopefully remove any of that fishy aroma and flavor. Months later when he decanted the spirit, he noticed a marked color and flavor change. So naturally the entire whiskey industry started doing it and everyone drank happily ever after. The end.Anyway, the charring has a profound chemical effect that in turn affects how the flavors of whiskey form and mature. The fire breaks down compounds called hemicelluloses into simpler sugars which are then caramelized adding sweetness in flavor and aromas. These caramelized sugars are also what give whiskey its color (for those who don’t know, whiskey initially comes off the still looking like water).
Another set of compounds in oak, called lignins also change during the charring process. Upon heating these compounds vanillins form, which as the name implies, taste and smell like vanilla. Further heating of oak lignin releases volatile phenols which can smell smoky, burnt, or medicinal.
Perhaps one of the most prominent effects that charring has on American oak is increasing the amount of oak lactones. These compounds are naturally present in all oaks, but American oak has an abundance of the more flavorful lactones. These are the compounds responsible for the woody, coconutty aromas that are so prominent in American malt whiskies and bourbons.
Lastly, the charring process breaks down the oak tannins that would normally cause bitterness or astringency. This makes the effects of oak on whiskey a bit more palatable to the average person. The tannins also play a role in oxidizing whiskey and give it a more delicate and “mature” aroma. This effect takes time to properly achieve, but as many of you know, a properly aged whiskey is certainly worth the wait.
American oak and its effects on whiskey are not completely understood and certainly things get a quite a bit more complicated than the simplified version that I’ve presented here. Things like the temperature and humidity of the barrelhouse, thickness of the barrel staves, size and geometry of the barrel, and even whether the barrel is laying on its side versus standing up straight can all have enormous effects on how the finished spirit hits the bottle.
Now when beer is laid onto that new oak, will we taste the same notes and flavors as we'd find in the spirits that go in these barrels? That just might be a call that you make when you try our anniversary variations.
|Matt Strickland is a brewer, distiller, and all around nice guy for Corsair Artisan Distillery, a small craft distillery located in Nashville, TN. Recently voted Craft Distillery of the Year by Whisky Magazine, their smoked whiskey (Triple Smoke) was also named Craft Whiskey of the Year by Whisky Advocate Magazine. He, too, is located in Nashville because living somewhere like New York would be one serious drive to work.|