September marks National Bourbon Heritage Month– a coveted time of year for Kentuckians and whiskey lovers everywhere. As a Louisville-based company, it’s in our blood to join in celebrations of the heritage and ongoing role Bourbon has played in our local economy, history, and culture. So grab a dram of your favorite whiskey and join us as we explore the magic behind some of bourbon’s signature flavors.

1. Yeast

Like many spirits, bourbon is distilled from a fermented mash of grain, yeast, and water. When in the presence of oxygen, this microscopic organism multiplies vigorously; but when all the available oxygen is used up, that’s when yeast begins converting sugar into alcohol and carbon dioxide. This process is called fermentation.

Sounds simple enough, but its actually a lot more complex than that. Even though they all essentially do the same thing, the type of yeast used has a huge impact on flavor– there’s a reason why some brands have been cultivating the same yeast strain for generations!

Yeast contributes many of the fruity, floral, green grass, soapy, sour, and sulfuric notes in a bourbon– everything from banana, green apple, and lavender, to wax, dill pickle, and egg. As The Bourbon Book describes, these profiles can be “fragrantly rich in the nose and add piquant tang to the palate; they can also bring a fresh, open quality that balances out the richness of other notes.”

Of course, changes in temperature, pH, oxygen, and nutrient levels, as well as competing bacteria, can impact the yeast and affect the consistency of all of these flavors. That’s why quality control, yield, and prevention of off-notes is incredibly important to the outcome of a bourbon.

2. Grain

To be a classified as a bourbon, the mash bill must contain at least 51 percent corn, though most bourbons tend to average about 70 percent.

Other grain staples– think rye, barely, and wheat– are typically added to the mash bill in varying amounts for flavor; though there’s plenty of examples of alternative grains like oat, brown rice, and triticale being used experimentally or in premium products. Here’s what you need to know about the four traditional grain sources:

  • Corn, bourbon’s dominant grain, provides much of the sweetness that the spirit is known for. With additional aging, vanilla and maple syrup flavors can give way to more complex notes.
  • Rye is responsible for many of bourbon’s spicier flavors, like black pepper, anise, and mint; and can also emphasize the clove and nutmeg profiles imparted by the barrel. Where mouthfeel is concerned, rye will sometimes create a leathery, dry experience.
  • Barley can be used malted or un-malted. When allowed to sprout (malt), it produces a distinctive character of the grain that many simply recognize as malt; however, it can also introduce nutty, smokey, or chocolatey elements. When un-malted, it is thought to add bright, sharp, and sometimes sour notes– think citrus or orchard fruit.
  • Wheat, though less common, acts as a “softening agent.” It can add undertones of subtle creamy, bready, and honeyed notes which nicely complement the bolder flavors derived from other sources.

The Bourbon Book describes how these grain aromas and flavors “provide structure for the subtler notes” of a bourbon which result from other parts of the production process.

3. Wood

One of the requirements for bourbon is that it must be aged in new, charred white-oak containers.

During its time in the barrel, bourbon gets much of its flavor from the wood itself. Everything from how much the barrel is toasted or charred to barrel size, rickhouse location, climate, and amount of time rested will affect what flavors are imparted on the bourbon inside.

The magic of maturation is that you can get a range of possible outcomes– which is why a master distiller is often tasked with monitoring the quality of the product that comes out of the barrel. Nevertheless, it is generally understood that the maturation process is both additive and subtractive, adding bold, spice flavors along with sweet aromatics to balance out harsher notes.

When toasted, heat causes a chemical reaction that allows for evaporation, extraction of tannins, and release of wood sugars. This process is what creates many of the sweet, warm, and woody character of a bourbon– think vanilla and caramel, coffee and baking spices, butter and walnut.

Similarly, charring can bring out more of a smokey, nutty profile while emphasizing equally complex and aromatic flavors– tobacco, coconut, licorice, black pepper, and more.

Nose, Taste & Finish

Now that you understand bourbon’s diversity of flavor, it’s time to explore.

Typically, bourbons are reviewed according to nose, taste, and finish. Nose and taste are easy to explain: nose encompasses the aromas of a bourbon while taste describes its flavors; but finish involves attention to the nature of a bourbon’s mouthfeel and flavor as you swallow– essentially how quickly a bourbon leaves your mouth and what happens as it does: is it smooth or harsh? Does it linger or fade quickly? Are there specific flavors to note? These would all be characteristics of the finish.

As you sip your way through new spirits this September, challenge yourself to try and identify some of these aromas and flavors of bourbon. You might just find a new favorite drink!

Have a beverage vision of your own? The beverage development experts at Flavorman would be glad to help you bring it to life! Just fill out this web form or give us a call at (502) 273-5214 to get started.

If you’re interested in learning the art and science of distilling, see our sister company and educational distillery, Moonshine University.


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Written on September 23, 2020.