These days, brands such as Pappy Van Winkle, Weller, and Elijah Craig with age statements reaching up to 20 years and beyond have the consumer crazed for extra-matured whiskey. This is a relatively new phenomenon, but as the demand for these whiskeys continues to skyrocket, producers are trying to figure out how to age their whiskeys for longer.
You might think this is as simple as leaving whiskey in the barrel, but that is far from the case. There are a lot of things to consider if you want to age a whiskey that’s worth the wait.
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The Seasoning of the Oak
Let’s start with the wood.
The most popular wood used in American whiskey is American white oak, or Quercus alba. It is mostly composed of cellulose, hemicellulose, lignin, tannins, proteins, fatty acids, and polysaccharides. Obviously, you can’t just cut down an oak tree and rush it into a barrel—first, you have to season the wood.
Broadly, the point of seasoning the wood is to change the chemical composition in a way that will develop more desirable color and flavors for your whiskey. Seasoning is the process in which the wood is dried to adjust the moisture content. There are two common forms: kiln-dried and air-dried. The kiln is quicker, while air drying can take from six months to more than three years in some cases.
The upside to kiln drying is expedience. It is less expensive and more readily available. The downside is that it doesn’t allow the time for the chemical compounds in the wood to break down and develop. In air drying, ultraviolet rays from the sun penetrate the wood and travel through the lignin to the cellulose and hemicellulose. This energy transfer is crucial to the breakdown of the wood sugars in the hemicellulose into simple sugars.
While the goal of seasoning is to lower the moisture content in the wood, the process is more complex than that. Some moisture is necessary to promote microbial growth that will continue to help break down these wood sugars. Lignin—famous in the whiskey world for transforming into a number of flavor compounds such as vanillin, which gives whiskey its recognizable vanilla notes—requires fungal influence to degrade the presence of microorganisms linked to chemical transformation of wood. Seasonal changes such as temperature swings also help in the process.
If you plan to mature your whiskey for decades, make sure you have wood that has been properly seasoned to avoid green notes or other off-notes that could hinder your product over time.
Virgin Barrels
In the United States, we tend to use new (or virgin) oak barrels to mature our whiskeys. That means that the barrel has never been used for anything else. We do that to extract a deeper color and richer variety of flavors, but it also means that we have more access to the bitter tannins in that wood.
Temperature and humidity play a huge role in this. As temperatures rise, the wood expands, and that makes it easier for the whiskey to enter the staves and dissolve the wood sugars and tannins. When temperatures drop, the wood contracts, which pushes the whiskey back into the barrel. I like to think of it as the barrels breathing in and out as the seasons change.
This seasonality is critical, and it’s why most barrel warehouses are not temperature-controlled. In some parts of the United States, these seasonal changes can be extremely dynamic, especially compared to the likes of Ireland and Scotland, where the temperature is relatively consistent throughout the year. It takes longer for those barrels to breathe, which is why you see such elevated age statements on Irish and Scottish whiskeys.
Because Irish and Scottish whiskey have to sit in a barrel for so much longer, producers often opt to put it in used cooperage, to avoid what we call “over-oaking.” Over-oaking occurs when the whiskey spends so much time in a barrel that you move past any semblance of balance or complexity, and everything starts to taste like a pencil.
Fermentation
Besides the choice of your grains and their proportions in your mash bill, fermentation is where you’re going to cultivate the flavors for your whiskey.
These flavors are called congeners and esters, and it’s important to develop a lot of these for a product you plan to mature for a long time. They will evolve and change into complex flavors that can balance out the influence from the tannins.
One way to to produce more congeners is to use multiple yeast strains. Each individual yeast strain will produce a different set of congeners and esters. Longer fermentation can also help—in that case, the idea is to allow the yeast more time to finish their job, focusing more on the production of flavors than on yield. That might also mean controlling the temperatures of your fermentations, to keep the yeast from dying off.
Distillation
Once you’ve produced a distiller’s beer jam-packed with congeners, you don’t want to throw all that hard work out in the distillation process.
Consider what kind of still you are using, and take a wider hearts cut. To be clear, I’m not saying to include harmful alcohols such as methanol or acetone into your hearts; instead, lean heavier into the tails cut. The tails contain higher alcohols and fusel oils. While these can lead to off-flavors in a clear or young spirit, they can also turn into something really amazing over a longer maturation period.
Barrel Treatment
We’ve already discussed the importance of proper wood seasoning. When constructing the barrel, consider a longer char to create a deeper layer of caramelized wood sugars.
The deeper the penetration of the char, the longer it will take for the whiskey to get to green wood that could lead to over-oaking. However, avoid extreme char levels, such as a number four or alligator char. The charcoal layer is there to work as a filter for the whiskey. As the whiskey moves in and out of the staves throughout the seasons, it moves through that charcoal layer, which works just like a Brita filter does in your home: It is removing impurities from your spirit.
If you’re trying to put out a whiskey more quickly, perhaps you could consider a heavy char that will filter your spirit in a shorter period of time. However, that isn’t necessary with long-term maturation, where the whiskey can filter slowly.
Barrel Size
If possible, consider using larger cooperage.
When a lot of craft producers first start making whiskey, some opt to use smaller cooperage because in small barrels, there is more spirit-to-wood interaction, which can help speed up part of the maturation process.
The same can be true in reverse, with larger cooperage having less spirit-to-wood interaction, and therefore slowing down the aging process. The industry standard barrel in America is 53 gallons, but that doesn’t mean you couldn’t go with something bigger, such as 59 or even 79 gallons.
Barrel-Entry Proof
The strength of the spirit going into the barrel matters, and going in with a lower proof can help with long-term maturation.
The U.S. Alcohol Tax and Trade Bureau (TTB) says the maximum proof you can put into a barrel for American whiskey is 125 proof. Many distillers go right up to that mark because it helps with maximizing yield on the back end.
However, different wood sugars and tannins dissolve in alcohol versus in water. At a higher proof, you’re going to dissolve more alcohol-soluble elements, including tannins. Softer and fruitier elements tend to be more water-soluble, so by going into the barrel at a lower proof, you set yourself up for a more balanced flavor profile over time.
Warehouse Conditions
Finally, the type of warehouse you use—wood or metal or brick—can impact the way that your whiskey matures.
The ventilation of that warehouse is important, and barrels stored near the top of a warehouse are going to be exposed to more heat than those stored at the bottom. The humidity level inside that warehouse is going to impact your evaporation rate and whether you are losing more alcohol or water over time. All these factors are going to impact your whiskey.
The angel's share is inevitable, but if you want there to be anything left in that barrel when it’s time to bottle, you have to figure out how to control these factors. Plus, if you’re going into the barrel at a lower entry proof, you won’t want to lose so much alcohol that you drop below whiskey’s legal 80-proof minimum.
There’s a lot to consider, but with these factors in mind, you can set yourself up for success in the long run. That said, always be tasting your barrels—and remember that older doesn’t always mean better. Bottle your whiskey when it’s ready to be bottled, not based on a preconceived age statement.
