Bourbon whiskey is synonymous with Kentucky, but it can legally be produced anywhere in the United States. Its distinctive character is shaped by a clear set of production rules. Bourbon must be made in the United States from a mash of at least 51 per cent corn, distilled to no more than 160 proof, and filled into new charred oak containers at no more than 125 proof. Unlike Scotch, it does not require production in one particular state, even if Kentucky remains its historic and commercial heartland.
If matured for at least two years and produced according to the legal requirements, it may be labelled Straight Bourbon Whiskey. Any straight bourbon aged for less than four years must display an age statement on the label. Bourbon itself must be made from a mash containing at least 51 per cent corn.
The use of new charred oak has a significant influence on bourbon's flavour. The interaction between spirit and heavily toasted wood helps create the vanilla, caramel, toffee and sweet spice notes that are so commonly associated with the style. Because the barrels are always new, oak tends to play a more immediate and prominent role in bourbon than it does in many other whiskies.
Most of the world's bourbon is still produced in Kentucky, and the state remains the centre of the industry in both scale and reputation. Its hot summers and changing seasonal temperatures help accelerate maturation relatively quickly, which is one reason extremely old bourbons are much less common than very old Scotch whiskies. Even so, well-aged bourbon does exist, and at its best can deliver great concentration with remarkable balance.
