04/21/24
By Rebecca Herman McBrayer

As discussed in Bourbon Whiskey, there are some common flavors that are noted when tasting bourbon. We recently discussed the contribution of grains to the taste of bourbon. For this Sunday Spirit Note, the focus is on the impact of the yeast strain, used in fermentation, to the aroma and taste of bourbon.

Yeast and Aroma – Esters

During the fermentation stage of making spirits, yeast is added to the mash and it begins converting the sugars in the mash to alcohol and carbon dioxide. The aromatic compounds that are produced by yeast as a byproduct of fermentation are called easters. These esters vary among yeast strains, for example, some yeasts produce a fruity scent, while others leave a bourbon with a hint of spice, herbs, or flowers.

Yeast and Flavor – Congeners

Yeast also plays a vital role in shaping the flavor profile of bourbon. As yeast acts to convert sugars into alcohol, it creates flavor compounds known as congeners. Each yeast strain produces different congeners and at varying levels. These congeners can be fruity, floral, or strong aromatic flavors. This is similar to how grape varieties influence wine. This diversity in yeast strains and their congener production accounts for the wide range of flavor experiences found in different bourbons. Yeast, therefore, holds significant importance in determining the distinctive taste of each bourbon.

Distillery Proprietary Yeast Strains

Historically, distillers have been known to carry their prized yeast in a Yeast Jug. Some would never let it out of their sight. They wanted to protect and nurture it so their signature strain would be ready for fermentation. While this is often associated with moonshiners, there is a Yeast Jug on display at Jim Beam.

Proprietary yeast strains play a crucial role in shaping the distinctive individuality of bourbon brands. Many distilleries possess proprietary yeast strains that heavily influence their bourbon’s flavor profile, keeping their composition a closely guarded secret.

The preservation of yeast strains ensures the continuation of a distillery’s signature style, as seen in the case of Wild Turkey, which has used the same yeast strain for over 60 years, resulting in a renowned “boldness.” Jim Beam’s yeast has been used in their bourbon-making process since Prohibition ended, ensuring a distinctive and consistent flavor profile.

Distillery Yeast Examples

As mentioned above, bourbon distilleries use proprietary yeast strains to create unique flavors and aromas in their products. Bellow are a few examples.

– Old Forester uses a proprietary yeast strain called 1B, which gives the bourbon a fruity forward taste, especially banana.

– Wild Turkey has used the same yeast strain for over 60 years, and many say it gives the bourbon a “boldness” that’s “musty, punchy, nutty and rich.”

– Jim Beam’s yeast is known for giving bourbon a “foxy” taste, which is different from other producers. It’s a closely guarded family secret that has been used since Prohibition ended in 1933.

– Woodford Reserve Kentucky Straight Bourbon Whiskey uses a proprietary yeast strain called 72B, which was developed specifically for the brand and contributes to its distinctive flavor profile with notes of vanilla, nuts, oak, cinnamon, nutmeg, caramel, spice, leather, tobacco leaf, and maple.

– Maker’s Mark uses a strain of yeast that the Samuels family has used for generations, and the yeast gives the bourbon a mouthwatering, fruity taste.

– Heaven Hill Distillery’s yeast strain has a robust complexity that includes sweet, cocoa, oak, grains, fruits, and spices. Some say that yeast can create floral, nutty, or extra fruity flavors.

Four Roses – A Different Approach

Four Roses Bourbon produces a wide range of flavors by blending various yeast strains and mash bills. The use two mash bills – Mash Bill B emphasizes rye, while Mash Bill E prioritizes corn. Five yeast strains impart unique characteristics. These elements are combined to create ten distinct recipes as indicated on the table below.

	Mash Bill B – 60% Corn, 35% Rye, 5% Barley	Mash Bill E – 75% Corn, 20% Rye, 5% Barley
Yeast V – delicate fruit	1 – OBSV – delicate fruit and rye	6 – OESV – delicate fruit and caramel
Yeast K – slight spice	2 – OBSK – rye and baking spice	7 – OESK – baking spice
Yeast O – rich fruit	3 – OBSO – rich fruit	8 – OESO – rich fruit and vanilla
Yeast Q – floral essence	4 – OBSQ – rye and light floral character	9 – OESQ – delicate grains and floral character
Yeast F – herbal notes	5 – OBSF – delicate rye and mint	10 – OESF – light grain and mint

Conclusion

When you taste bourbon and pick up various flavors, connect to its source and consider the contributions made by the specific yeast strain used by the distiller(y).

There are many more sources of bourbon flavors. As noted in other Sunday Spirit Notes, this includes, grain selection, fermentation process, barrel selection and preparation (level of toast and char), entry proof into the barrel, the storage environment, and even decisions made for bottling. With so many variables, it is no wonder that there is such a wide range of bourbon flavors and why five people tasting from the same bottle may pick up different notes and have varied preferences.

Happy Tasting!
Rebecca