The primary grain ingredient in bourbon whiskey is corn.
Bourbon is an American whiskey whose mash bill must contain at least 51% corn. Distillers combine the corn with other cereal grains, commonly rye, wheat, or malted barley. Corn supplies much of bourbon’s characteristic soft, sweet flavor, while the secondary grains shape its spice, fruit, malt, and texture notes.
After fermentation and distillation, bourbon must be aged in new, charred oak containers. The charred wood contributes color and flavors such as vanilla, caramel, toast, and spice. Bourbon can be produced anywhere in the United States, although Kentucky is historically and commercially associated with the style.
Rye, wheat, and barley are common sources of confusion because all may appear in a bourbon mash bill. Rye bourbon tends to taste spicier, while wheated bourbon is often softer and rounder. Barley is usually present in smaller amounts because malted barley helps convert starches during mashing. Bourbon has no general minimum aging period, though “straight bourbon” must be aged for at least two years.