Here in the heart of bourbon country, it's the time of year when people start to grow weary of the heat and humidity and look forward to the cooler days of autumn. Harvest season in Kentucky brings colorful fall foliage, crisp temperatures, and evenings spent gathered around backyard fire pits.

The smells and flavors we associate with this time of year begin to change as well. Menus shift from corn on the cob to sweet potato pie. Juicy cheeseburgers give way to sliced turkey topped with a hefty amount of homemade gravy that almost seems unreasonable. Store bought candles start to transition from honeysuckle to pumpkin spice.

Smells and flavors are at the heart of our work in the whiskey industry. What matters most is how the liquid in the bottle tastes. Oak chemistry can be complex, but one thing is clear: charred American oak barrels can contribute an incredible range of flavors. Many familiar flavors found outside the world of whiskey can be derived directly from oak.

There's even a degree of seasonality to some of those flavors. Much like brewers create seasonal beers, whiskey makers can create seasonal expressions by extracting specific flavor compounds from the oak. The result is a whiskey that captures the same tastes and aromas people gravitate toward as the seasons change.

With that in mind, let’s highlight a few familiar fall flavors and see which ones we can get directly from oak:

Cinnamon ☑

We get cinnamon from different combinations of lignin degradation byproducts.  Lignin makes up approximately 25% of the oak tree.

Clove ☑

Notes of clove come directly from eugenol, a byproduct of lignin degradation and the main component found in clove oil.

Baking Spice ☑

Isoeugenol can present itself as a bouquet of different baking spices. As part of the eugenol family, this also comes directly from the pyrolysis of lignin.

Smoke ☑

Guaiacol is our key marker for smoky aromas and flavors. This is near the end of the lignin degradation pathway.

Roasted nuts ☑

Unlike the above, this comes from the degradation of hemicellulose, which makes up about 22% of the oak tree. Furanic components have a wide range of sweeter flavors and toward the top of the temperature scale we get furfural, which provides those nice nutty flavors.

Pumpkin Spice ⮽

Sorry Starbucks fans, but there isn’t a whole lot we can do to get this iconic (some might say overused) flavor of autumn.

Five out of six… not bad, right?

We capture these seasonal whiskey flavors using our patented toasting technology. This allows us to concentrate these flavors to more perceivable levels in the oak.

The science here isn't overly complicated. Heat white oak to a specific temperature, and specific flavors begin to emerge. Lighter toasts generally produce sweeter notes (there are some exceptions), while hotter toasts create richer, darker flavors. By carefully controlling the toasting process, we can emphasize specific flavors in the finished whiskey.

Much of this is driven by the breakdown of lignin within the oak. As heat increases, lignin transforms into a variety of aromatic compounds that contribute familiar flavors and aromas to whiskey. The lignin pyrolysis pathway is shown below.