Everyday alchemy, coffee roasting coaxes golden flavor from a bland bean. Unroasted beans boast all of coffee’s acids, protein, and caffeine—but none of its taste. It takes heat to spark the chemical reactions that turn carbohydrates and fats into aromatic oils, burn off moisture and carbon dioxide, and alternately break down and build up acids, unlocking the characteristic coffee flavor.
A note on flavor: Describing the tastes of different roasts is as subjective as putting a wine into words. In both cases there’s no substitute for your own personal taste, so sample away! (Many descriptions below are based on Kevin Knox and Julie Sheldon Huffaker’s Coffee Basics: A Quick and Easy Guide.)
Light
Aliases: Cinnamon roast, half city, New England
Roaster Watch: After about seven minutes the beans “pop” and double in size, and light roasting is achieved. American mass-market roasters typically stop here.
Surface: Dry
Flavor: Light-bodied and somewhat sour, grassy, and snappy
Medium
Aliases: Full city, American, regular, breakfast, brown
Roaster Watch: At nine to eleven minutes the beans reach this roast, which U.S. specialty sellers tend to prefer.
Surface: Dry
Flavor: A bit sweeter than light roast; full body balanced by acid snap, aroma, and complexity
Dark
Aliases: High, Viennese, French, Continental
Roaster Watch: After 12 to 13 minutes the beans begin hissing and popping again, and oils rise to the surface. Roasters from the U.S. Northwest generally remove the beans at this point.
Surface: Slightly shiny
Flavor: Somewhat spicy; complexity is traded for rich chocolaty body, aroma is exchanged for sweetness
Very Dark
Aliases: Italian, espresso
Roaster Watch: After 14 minutes or so the beans grow quiet and begin to smoke. Having carmelized, the bean sugars begin to carbonize.
Surface: Very oily
Flavor: Smokey; tastes primarily of roasting, not of the inherent flavor of the bean