By Tim Korby

With whiskey ~ and specifically, bourbon ~ sales being at an all-time high and taking a bite out of families’ household wine budgets, I’ve decided to find out what all of the hullabaloo is about. Single-malt scotch sales started surging in the ’80s and continue to grow today, but the bourbon boom is a more recent phenomenon. What exactly is whiskey and what are the differences between bourbon and scotch?

In general, whiskey or whisky (the latter spelling usually used for Scotch) is a distilled alcoholic beverage made from fermented grain (corn, barley, rye and/or wheat), which is usually aged in charred, white oak barrels. The first and most obvious difference between scotch and bourbon is that Scotch whisky must be produced solely in Scotland and bourbon must be made in the United States (mostly in Kentucky). Another difference is the grain that is used as the base for each product. Scotch is made predominantly from malted barley (single-malt scotch from 100 percent malted barley), and bourbon is made from corn (at least 51 percent but usually more than 70 percent). The barrel aging for the two whiskeys is also different; bourbon is aged for a minimum two years in only new barrels, whereas scotch must be aged for at least three years but in barrels that may have been previously used. In single malts from the northern Scottish islands, the malted barley used to make scotch is dried in kilns that are fired by peat. It is the peat smoke that imparts the strong and distinctly smoky/earthy flavor to the final product.

There are many more types of whiskey than just scotch and bourbon. Irish whiskey was the fastest-growing whiskey category in the U.S. last year. It is made exclusively in Ireland, where barley is used as the base grain. Irish whiskey must be aged in wooden casks for at least three years. Canadian whiskey (of course, made only in Canada) has a blended multi-grain base that contains a large percentage of corn, but it is the rye in the grain mix that imparts the unique flavor. Canadian whiskey is typically lighter and smoother than other whisky styles. It may also contain caramel (as may Scotch whisky, but not bourbon).

Rye is also used in the U.S. to make American rye whiskey, another fast-growing category. Rye whiskey must be at least 51 percent rye, to which corn and malted barley are usually added. Rye whiskey must be aged for at least two years in new barrels. Rye whiskey tends to be a bit spicier and fruitier than corn-based bourbon, which tends to be a bit sweeter and more full-bodied.

The newest commercial phenomenon on the whiskey shelves is white corn whiskey, which is marketed as a form of legal “moonshine.” Because white corn whiskey sees no barrel aging, it has no taste resemblance to any of the brown whiskeys.

I have merely scratched the surface here with the multitude of styles of whiskey available. Knowing this, next time I go to the bar, I’ll be more specific than just saying “Bartender, give me a shot of whiskey.”

Tim Korby is the director of Julio’s Liquors and the-AngelShare.com online wine store. He started in the wine industry in California in 1976 and moved to the Boston area in 2000. In addition to being a retail wine buyer, he has taught wine courses since 1984 and has regularly written newsletters, articles and blogs since 1981. Tim travels the world several times a year to find just the right wines for his customers and to learn the true romance of the wines he sells.