The Aging Process
So, once we have influenced the flavor of your favorite whisky through ingredient selection and through variations in the distilling process, all that remains is aging. The big one. The one that will ultimately determine whether or not you like the taste of that dram.
But, first things first. That age statement on your whisky bottle. That’s how long it spent in a wooden cask tucked away in some warehouse. Once the whisky is in the bottle, that’s it. No more aging.
But, while it’s in the cask, there’s lots and lots going on. For a closer look, we’ll need to dive back in our chemistry world to see what’s happening between the whisky and the wood in the cask. Let’s start with the wood itself. It’s almost always oak. That’s because oak is nice and hard and durable, but it also has lots of little pores in it. So how does chemistry come into play? Lots of ways. First, they set the cask on fire before they use it. This creates a thin charcoal layer on the inside. And charcoal is a friend of whisky flavor, because it’s really just melted cellulose sugars from the wood. This melted sugar dissolves into the whisky and gives it a caramel and vanilla flavor. And sometimes a nutty taste, too. At the same time, some of the whisky seeps into the little pores in the wood. In there, chemicals in the oak called lignin slowly dissolves into the whisky. This makes it taste like fruit and flowers. Lastly, there’s other stuff in the oak called tannin. Over time, this adds a coconut flavor and adds to the spiciness of the whisky. And of course, the longer the whisky spends in the cask, the more flavors get transferred.
So what else happens during aging? Well, if the casks are made from American Oak, the chemicals tend to make the whisky taste sweeter and more vanilla like. If they’re made from the more porous European Oak, the whisky tends to be a bit spicier. As well, the speed of the aging process is affected by how big the cask is. Small casks accelerate the process because there’s more surface area to interact with the whisky.
But perhaps the biggest impact on flavor is what was in the casks before the whisky people get their hands on them. We’re not talking pickles or fish. Wrong flavors. It’s stuff like sherry, or wine, or port, or rum, or bourbon that really makes the difference.
This part isn’t really chemistry. It’s just flavor transfer from whatever was previously soaked into the wood. But bourbon doesn’t get of that flavor transfer. That’s because bourbon can only be aged in new, unused casks. Why? Way back in the early days of American whisky, someone decided that only new, unused casks could be used for aging. So charring and time are the only real aging weapons available to American whisky and bourbon. Which is good news for all the other whiskies out there, because they have access to all the old bourbon casks. And old bourbon barrels have lots of old bourbon hiding in the pores of the oak, which adds lots of flavor to the Scotch or Irish whisky that uses them for aging. In fact, over the years, as supplies of port and sherry casks have diminished, the bourbon industry has become the chief source of barrels for aging everyone else’s whisky.
And that’s where it gets really interesting, because many modern distillers (except American) now incorporate a process called ‘finishing’ into their aging process. Thats where the whisky spends part of its aging life in ex-bourbon casks, followed by a shorter period in other casks. Distillers such as Highland Park, Redbreast, and McCallan love to finish in ex-sherry casks. Sometimes, they even skip the ex-bourbon casks and do ll of their aging in sherry. Other distillers, like Glenmorangie and Balvenie, prefer the port finish, or the rum finish.
Bottom line? All of these aging choices make for an endless supply of flavor combinations, with you as the chief beneficiary.
So, no matter what your taste preference, there is sure to be a whisky out there that will satisfy it. It’s all about the search. And that’s the fun part. Cheers and enjoy!