It is more complex (and interesting) than you think.
One would be forgiven for assuming that light roast coffee means mild-tasting; medium-roast coffee means, well, medium-strong tasting; and that dark roast has the strongest flavor. Simple, right?
But those people would be wrong — kind-of. If reaching peak coffee has taught us anything, it is that nothing about coffee is as simple as it appears.
Some Coffee Basics
As explained by the National Coffee Association (NCA) — an organization whose website will (you’ve been warned) quickly send you down a bottomless hole of coffee facts, information, and arcana — coffee beans come off the coffee tree as the green and spongy seeds of a coffee cherry, arabica being the most high-quality varietal. According to the NCA, arabica makes up 70 percent of the world’s coffee bean market. Its high quality and sensitive growing process also makes it the most expensive.
Those seeds, i.e., the coffee beans, are then separated, dried, and milled for bulk sale as dried green coffee beans. This is how they arrive at coffee roasters all around the world. Coffee only begins to degrade once roasted, so the closer the timeframe between roasting and selling to the consumer, the fresher it will be.
Coffee Roasting 101
Much like roasting food in an oven, roasting coffee brings out flavor, aroma, and character; it also evaporates moisture. Everything in the roasting process, however, is a matter of degree, as anyone who has ever had a raw roast chicken or an overdone pot roast can attest.
At its most basic, the level of roast (light, medium dark) simply reflects how long the coffee beans have been roasted. But it is the effect of those roasting times that makes things interesting.
Light roast has the lightest color (surprise, surprise) and produces coffee with less body, but more complex, delicate flavor. Because subtle aromas and flavors have not been cooked out of the beans, light roasts will show individual notes like caramel, nuts, fruit, and cinnamon. Light roast also has a little more caffeine than medium and dark roasts.
Medium-roast coffee is also known as American roast or city roast, and is the most popular in the U.S. In medium roast, some flavor notes are still there, but with a more toasted flavor that may also have a little bitterness.
Coffee’s version of a charred, well-done steak, dark-roast coffee beans are dark, shiny, and bitter tasting. Many European-style beans are dark roast (French roast, Italian roast). Dark roast has the least acidity and most body, which is why it is commonly used for espresso.
Though not always, lower-quality beans can be used in dark roast. The beans’ inherent delicate flavors have been roasted away, leaving only the smoky or carbon flavor of the roasting itself.
No one roasting level is right or wrong. It is all just a question of preference.