Opening a bag of freshly roasted coffee beans can take you straight to olfactory heaven. While certain qualities of the final brew are determined by the origin of the beans and the way they've been processed, it's roasting that most influences the taste and fragrance. However, terminology to describe various roasting methods can be confusing.

The most obvious and influential variable is the darkness of the roast. Beans held longer at a higher temperature become more caramelized, and more oils come to the surface. Traditionally, French roast is the darkest of the regular coffees (excluding espresso), followed by Italian roast and then Vienna roast, which is only slightly darker than the standard American roast. Within these broad categories are dozens of variations, preference for which is often determined by cultural factors. Americans on the West Coast, for instance, tend to drink a darker roast than people on the East Coast.

Before they've been roasted, coffee beans have no real flavor. The heat of roasting dries the beans and draws out a volatile, oily substance. This substance isn't actually an oil, since it is water-soluble. This is where the flavor of the bean resides. It evaporates easily and can absorb other less desirable flavors, which is one reason to be sure your beans have been freshly roasted. The more moisture is lost, the more this oil comes to the surface, which is why darker roasts have a shiny look.

Dark Roasted Coffee Beans Are Gaining in Popularity
With the spread of Starbuck's, Peet's, and other West Coast coffee franchises, a taste for darker roasted coffee beans has followed. The unfortunate side effect is that some roasters show their inexperience, and turn out a bean that is burnt, not dark. A dark roast should taste bittersweet, a flavor that results from the slight charring of the proteins and caramelizing of the sugars. A good rule of thumb (or nose) is not to buy beans that have too heavy a smoke odor. Some smokiness is desirable, but it shouldn't smell like a cold fireplace.