Bourbon is made primarily from corn. By U.S. law, the mash bill (the grain recipe) must be at least 51% corn; the rest is usually a mix of rye, wheat, and malted barley. After distilling, it's aged in new charred oak barrels, which give bourbon its color and much of its flavor.
The mash bill: corn plus a supporting cast
Every bourbon starts with its mash bill — the recipe of grains that gets cooked, fermented, and distilled. Corn has to be the majority (at least 51%), and it's what gives bourbon its signature sweetness. The remaining grains shape the character:
- Rye adds spice, pepper, and a drier finish — the classic "high-rye" bourbon profile.
- Wheat softens things, giving the smooth, gentle character of a "wheated" bourbon.
- Malted barley is usually a small percentage, included mainly for the enzymes that help convert grain starches to fermentable sugars.
Water, yeast, and new charred oak
Beyond grain, two things matter enormously. Yeast ferments the sugars into alcohol and contributes its own flavors, and many distilleries guard their yeast strains closely. Then comes the barrel: bourbon must be aged in new, charred oak. That char is where a clear distillate picks up its amber color, plus notes of caramel, vanilla, and oak. No barrel, no bourbon.
The legal definition, in plain English
To be called bourbon, a whiskey must be made in the United States, from a mash of at least 51% corn, distilled to no more than 160 proof, put into the barrel at no more than 125 proof, aged in new charred oak, and bottled at no less than 80 proof — with no added coloring or flavoring. It doesn't have to be made in Kentucky, but roughly 95% of it is.
Taste how the grains change everything
The fastest way to understand a mash bill is to taste a high-rye next to a wheated bourbon, side by side. That's exactly what our Premium Tasting is built for — barrel-strength pours from multiple distilleries, straight from the cask. See all our experiences.
Keep reading: What is single barrel bourbon? · What is barrel strength? · Where does bourbon come from?