How Wood and Toast Levels Affect the Taste of Bourbon and Other Whiskeys

The barrels in which whiskey is matured are just as important to the final product as the ingredients and the distillation process. New, charred oak barrels are required for the aging of all whiskeys, including Bourbon, rye, wheat, malt, and Tennessee whiskey. Nonetheless, there is a wide range of possibilities within this requirement that can significantly alter the appearance, smell, taste, and texture of the finished product. Within these constraints, distillers can create whiskey with their own individual flavor profiles by carefully adjusting the char and toast degree of the barrels. Wood terroir varies by area, with trees growing more slowly and densely in colder regions, resulting in wood with concentrated flavors that may be more difficult to access and absorb.

Wood Type

The whiskey's ultimate flavor can be greatly affected by the type of wood used in its production. White oak is the most common type of wood used to make barrels, yet each piece of oak has its own unique terroir. For example, the slower growth of trees in colder northern latitudes produces grains that are tighter and, thus, offer more concentrated flavors. Distillers have to strike a fine balance when trying to get the ideal flavor profile, as some flavors are more difficult to access and absorb than others.

Whiskey Taste


Several distilleries and barrel houses favor using natural seasonings because it results in a more nuanced whiskey. Naturally aged whiskey has a larger variety of flavor and aroma constituents because the wood's disintegration during seasoning creates a more porous structure that the whiskey can interact with. Furthermore, bacteria present during natural seasoning can help the wood develop its own distinctive flavors.

Nonetheless, kilning yields a more consistent and reliable product, but one with a simpler flavor character. Some of the chemicals in the wood can be broken down by the high heat employed in kilning, leading to a more streamlined flavor profile in the final whiskey. Kilning, on the other hand, may produce uniformly aged barrels more quickly than natural seasoning, making it more appealing to large-scale cooperages and distilleries.

The Effect of Charring on Whiskey's Taste

Charring occurs after the wood has been seasoned and a barrel has been constructed. This is a vital stage in establishing the char's depth, which can last anything from a few seconds to an entire minute. The charcoal acts as a filter, changing or eliminating different congeners from the distillate. Whiskey's flavor and aroma come from congeners, which are byproducts of fermentation besides ethanol. Unfortunately, not every congener has a positive effect. Some potentially toxic congeners are eliminated during distillation, while the charred barrel handles the rest.

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Several flavor profiles can be created in barrels used for aging spirits like whiskey by toasting the wood to a specified temperature for a set amount of time. Heat from the toaster allows the wood's hemicellulose to degrade into sugars, which may then be removed during the aging process. Caramel, chocolate, and vanilla are just a few of the tastes that can develop from this. The flavor profile can be altered by performing the toasting process either before or after the charring of the barrel.

Independent Stave Co. barrels are toasted for 43 minutes and charred to the deepest level in general use, resulting in a 60-second burn, which is used by Wilderness Trail Distillery in Danville, Kentucky. Brown-Forman, the parent company of Jack Daniel's and Woodford Reserve, crafts its own barrels according to its own toasting and charring criteria. The oak barrels used to age Woodford Reserve are pre-char toasted, which breaks down the lignin into synapealdehyde, syringealdehyde, and vanillin, all of which contribute to the whiskey's signature vanilla flavor. The finishing barrel used for the Double Oaked Woodford Reserve is only charred for 5 seconds, compared to the ordinary Woodford Reserve barrel's 25 seconds.

While most distilleries employ charred barrels, others experiment using toasted barrels to get a more distinctive flavor character in their whiskey. Instead of releasing heavy smoky notes from charring, toasting the barrels can release more sugars and aromas from the wood. In some cases, this can add sweetness and complexity to the whiskey. Old Potrero's 18th century-style whiskey, however, cannot be designated a "rye whiskey" because it does not fulfill the legal criteria of that category due to the usage of un-charred barrels.