Bourbon Basics

• In order to be sold as bourbon in the United States, whiskey must be distilled in the U.S. from at least 51 percent American corn. The amount of alcohol in the whiskey is regulated at every stage of the distilling and aging process, and the finished product should be no more than 80 proof, or 40 percent alcohol by volume. To be considered bourbon, the whiskey must also be aged in new charred oak barrels. By contrast, Scotch whisky is aged in barrels previously used to store wine or other types of alcohol.

Not Straight to the Shelf

• In order to be sold as straight bourbon, bourbon must not only meet these basic criteria but also a more stringent set of rules. Straight bourbon must be aged for at least two years. In fact, it is often aged for at least four; straight bourbon aged less than four years must specify its age on the label. Lastly, to be straight bourbon, a bourbon must be free of any additional colors, flavors or other types of spirit.

Blended Bourbon

• The main alternative to straight bourbon is blended bourbon, which combines straight bourbon with other spirits. This may be a mixture of multiple straight bourbons, or may mean that part of the mixture is made up of un-aged grain spirits. However, 51 percent of a blended bourbon must consist of straight bourbon. If the percentage of straight bourbon is below this level, it will be advertised as blended whiskey rather than blended bourbon.

Tasting the Difference

• Neutral grain spirits are usually added to bring down the cost of a whiskey; because they don't require the same lengthy aging process, they're much less expensive to produce. However, they lack bourbon's distinct flavor. As a result, the mixture may feel bland or diluted compared to the oaky or fruity flavor of straight bourbon. This doesn't mean blended bourbon is bad, however. It can be a good introduction to bourbon for first-time drinkers, as well as an ingredient in a wide range of cocktails.