What is bourbon made from

Bourbon is the classic American whiskey, distinguished by its specific production requirements and geographic origins. 

To be legally labeled as bourbon, the spirit must adhere to several criteria, namely that it must be made in the United States (not just Kentucky), be distilled to no more than 80% ABV, matured in new, charred oak barrels, and have no additives other than water.

Its mashbill must also be at least 51% corn. In this article, we’ll explain what bourbon is made from, why corn is so important, as well as covering the roles of water, yeast, and wood. After all, it’s these strict guidelines that help ensure that bourbon maintains its distinctive character, differentiating it from other types of whiskey. 

If you like your American whiskey, be sure to check other recent articles on the distilling tradition of bourbon and rye and Is Jack Daniel’s bourbon? 

The grains that make bourbon: corn

Bourbon history is intertwined with the agricultural practices of early American settlers, particularly in Kentucky, and owes its unique character and global reputation to its primary ingredient: corn.

The late Ova Haney, former master distiller at Four Roses, was once asked “Why is bourbon made from corn?” His reply was “Because that is what grows in Kentucky. If Kentucky grew rice it would have been made from rice.” 

In Kentucky, and the wider American South, corn was a staple crop in the early days of the country. The fertile lands of the American frontier were well-suited for growing corn, which became a surplus crop for many farmers. 

Throughout the 18th century, the significance of corn in bourbon production increased. At the time, distilling the excess corn into whiskey was a practical solution for preservation and transport. It also offered an alternative source of income. 

What began as a practical solution for farmers to make money became the bedrock (or, if I may, the cornerstone) of bourbon’s style. Corn contributes a creamy, mellow, natural sweetness while creating a foundation for other grains in the mash bill to add complexity and depth.

A legal requirement for bourbon to be made from a grain mixture that is at least 51% corn was implemented with the passage of the Federal Alcohol Administration Act in 1935, as part of the United States government’s efforts to regulate the alcohol industry following the repeal of Prohibition in 1933. Bourbon was further recognized in 1964 by the U.S. Congress as a “distinctive product of the United States”. The mandatory mashbill preserves the traditional recipe of bourbon and means it can be differentiated from other types of whiskey. The regulation ensures that bourbon retains its sweet, full-bodied flavour profile, a direct consequence of corn’s natural sweetness.

The grains that make bourbon: rye, wheat, and barley

While corn is the cornerstone (sue me) of bourbon, other grains play crucial roles in shaping its flavour too. Namely rye, barley, and wheat, all commonly used as secondary grains in the mash bill. 

While we’re on the subject, a whiskey mash bill is the specific recipe of grains used to produce whiskey, dictating its flavour profile and character. It’s basically the recipe. Everyone clear?

Now let’s talk through each of the secondary grains that contribute distinct characteristics to the bourbon:

Rye: Known for adding a spicy, peppery note to bourbon, rye brings a complexity and depth that balances the sweetness of corn. Rye-forward bourbons, such as Bulleit Bourbon, are celebrated for their boldness and vibrant spice profile, appealing to those who favour a whiskey with a bite.

Wheat: Wheat offers a softer, smoother contrast to rye, with a gentle sweetness that complements the robustness of corn. Wheated bourbons like Maker’s Mark are prized for their mellow, accessible flavours, often described as having hints of caramel, vanilla, and bread-like warmth.

Barley: Malted barley is primarily used in bourbon production for its enzymes, which are crucial for converting starches into fermentable sugars during the mash process. Beyond its functional role, barley imparts a slight nuttiness and richness, enhancing the overall complexity of the bourbon.

Water and yeast

Depending on who you ask, the amount of ingredients whisky has will differ. Grain and water are absolutes, a lot of people also say yeast, and some even count the barrel as an ingredient. We’re going to cover all bases here and treat all four as factors that make bourbon what it is.

First then is water, which plays a crucial role in the production of bourbon. Initially, water is mixed with the mash of grains to facilitate the conversion of starches into fermentable sugars during the mashing process. There’s also water used in fermentation, and some place a great deal of emphasis on the purity and mineral content of this water and how it can influence the fermentation efficiency and flavour of the final product. After distillation, water is often used to dilute the bourbon to the desired proof before ageing, affecting its smoothness and taste. In Kentucky, the water is limestone-rich and often naturally filtered, which some bourbon producers will say contributes to the distinctive smooth and sweet profile of bourbon by removing iron and adding beneficial minerals.

Onto yeast. The reason we have booze at all is thanks to yeast, as it converts the sugars of the grain into alcohol (and carbon dioxide). Over approximately three to five days, the yeast ferments the sugars, producing a beer-like liquid called “distiller’s beer” or “wash,” with an alcohol content around 7-10% ABV. This stage is not just about alcohol production; it’s also where distinctive flavors start to develop, influenced by the grain composition, yeast strain, and fermentation conditions. The choice of yeast and the fermentation environment are closely guarded secrets among distillers, as these factors significantly contribute to the bourbon’s final taste profile, adding fruity, floral, or spicy notes that distinguish one bourbon from another.

Finally, wood. As we’ve explained in the intro, bourbon must be aged in new, charred oak barrels. This law further distinguishes bourbon, as the charring process caramelizes the sugars in the wood, contributing to the whiskey’s flavour and colour, giving the whiskey notes of vanilla, toffee, and oak. There is no minimum aging period for bourbon as a whole, but to be called “straight bourbon,” it must be aged for at least two years. 

This interaction between the wood and the spirit, combined with the foundational flavors provided by the grain and fermentation, results in a whiskey that is deeply American in its heritage and taste: bourbon.

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