Regardless of whether it’s high-end, single origin or a simple cup of Folgers, the roast is the possibly the most important contributor to the overall flavor of a cup of coffee. The amount of time a bean is roasted influences the taste, aroma, body, and acidity of the resulting drink. Therefore, if you’re hoping to really get the most out of your coffee, it’s important to understand the difference between the various roasts and how they affect flavor.
The roasting process
Put simply, coffee roasting involves rotating the green beans in a rapidly heating chamber until they are cooked to the desired degree of doneness. During the roasting process the beans expand, which creates a cracking sound. Most roasts are determined not only by temperature but by the amount of times the beans have expanded, or “cracked.” Lightly roasted beans, for example, are often roasted to the point where the bean first cracks. Dark roasts on the other hand, involve roasting the bean until it has cracked twice.
Light roasted beans are cooked to an internal temperature of between 365°F and 401°F. During this process the beans expand and crack once when they reach around 205°F. Light roasted beans are light brown in color and have no visible oils on the surface.
Roasting beans to the first crack is commonly referred to as the New England Roast, while beans that are roasted to just before the first crack are categorised as Cinnamon Roasted.
For those who want to preserve as much of the the beans' original flavor, a light roast is the way to go. This roast is also used for milder coffees and single origin beans. Lightly roasting beans results in the coffee having very little body and a high acidity when compared with darker roasts. They also tend to taste fairly grainy and earthy as a result of the shortened roasting time.
The roasting process tends to burn away the caffeine content of coffee beans, therefore lightly roasted beans have a higher caffeine content than dark roasts.
This is the most commonly available roast around and in many ways offers the optimum balance between acidity, aroma, flavor, and body. Medium roasted beans are cooked to a temperature of between 410°F (American Roast) and 428°F (City Roast). The roasting process is stopped just before the second crack. These beans are medium brown in color and have no visible oils.
Medium roast beans lack the grainy taste of light roasts and also contain less caffeine. While it is muted somewhat, the origin flavors of the bean is still preserved in medium roasts, however the taste of the roast itself is also present.
Not quite a medium roast and not yet a dark roast, the medium-dark roast fits somewhere in the middle. This roast is often used on Indonesian beans and results in a dark brown bean with a small amount of oil on the surface. As beans are roasted the oils within begin to break through to the surface, which results in darker roasted beans having a oily sheen. These beans are cooked to an internal temperature of between 437°F (Full-City Roast) and 446°F (Vienna Roast). The roasting time will results in the beans cracking a second time.
These beans are notable for their heavy body, spicy flavors, and slightly bitter aftertaste. In the case of medium-dark roasted beans, a small amount of the original flavor is preserved, however the taste of the roast itself is dominant.
Finally we have the dark roast. These beans are either a deep dark brown or just shy of black and have a thick coating of oils. These beans are roasted far beyond the second crack to an internal temperature of between 464°F and 482°F. French Roast is the lightest of the dark roasts with Italian Roast being the darkest. Dark roasted beans are almost always used for espresso, although they can be enjoyed as regular brewed coffee.
Dark roast beans have the least caffeine of any roast, and none of the beans origin flavors are preserved. Instead the coffee is dominated by the flavor of the roast. Dark roast coffee has a heavy body and a smoky, burnt taste.