According to Federal regulations, for an American whiskey to be labeled as bourbon it must be made from a mash containing between 51 percent and 79 percent corn. If the corn content is higher, the product must be designated as corn whiskey and, according to the law, must be distilled at 160 proof (80 percent alcohol) or less and must be aged a minimum of two years in new charred oak barrels. As a practical matter, though, most bourbon is aged at least four years and often longer. Since it is a straight whiskey, no blending is permitted and there are no additives, with the exception of water to reduce the proof. Most bourbons are marketed as 80-proof products, but some, particularly the newer boutique, small-batch, single barrel and barrel proof products are much higher in alcohol content.
Often associated with bourbon, the sour mash method is simply a technique of fermentation that uses part (at least 25 percent) of the spent mash from a previous distillation in the new batch of fermenting mash. A sour mash must ferment for between 72 and 96 hours. One of the advantages of the sour mash methods is that it provides a dimension of consistency from one batch of whiskey to another. The sweet mash yeasting method, on the other hand, uses only fresh yeast for fermentation.
By law, bourbon can be distilled anywhere in the U.S., but the vast majority of it is produced in Kentucky, where it must be distilled and warehoused for at least one year in order to carry the "Kentucky Bourbon" designation on the label.
In recent years, the emergence of a group of high-quality, high-priced, high-proof bourbons bearing designations such as "single-barrel," "small-batch," and barrel proof" have helped bring a new level of interest and excitement to the American whiskey category.
Another whiskey designation, similar to bourbon, is Tennessee whiskey. Although its grain content need only be comprised of at least 51 percent of any grain, corn is usually used. Basically it is made in a similar manner to sour mash bourbon but Tennessee whiskey also includes an extra step in its production process - the distilled spirit is filtered through maple charcoal in large, wooden vats before agin in order to remove impurities. The most prominent Tennessee whiskies are Jack Daniels and George Dickel.
The other large category of domestically-produced whiskey is American blended whiskey, which is comprised of brands which have been created by carefully blending straight whiskies with grain spirits. At one time this category, which didn't even exist prior to Prohibition, accounted for about half the domestically-produced whiskey consumed in this country. The category's share of the total market has been steadily eroding over the past 25 years, but it remains significant nevertheless, primarily due to its two biggest brand - Seagrams 7 Crown (2.8 million cases) and Kessler (1 million cases).
When considering blended whiskies, the important thing to remember is that they are built. The straight whiskies that go into them are distilled and aged to take a planned part in the blend. Every blend on a store's shelves has a number of straight whiskies in its formula. By law, a blended whiskey must contain a minimum of 20 percent straight whiskey. A premium brand may contain as many as 75 different straight whiskies and grain neutral spirits. The purposed of blending is to created a balanced, light-bodied whiskey, with a richness in taste and an individual character of its own. Balance is achieved because the blending art assembles a variety of elements into a unique and distinctive product. Another hallmark of whiskies is their consistency of taste.
