Bourbon, among its many codified restrictions, must be at least 51 percent corn. After that, though, the bourbon distiller has some discretion in picking the mix of secondary grains. Most use rye and barley. A few, like the Van Winkle brands, use wheat. That was made popular by Julian’s grandfather. His biggest contribution to modern bourbon is that he was the first to make and sell a mass market fine whiskey with wheat as its dominant secondary grain.
