When you think of a Thanksgiving turkey, the image in your head probably doesn’t include the raw, unstuffed bird sitting on your countertop. I bet you’re actually picturing a perfectly basted, golden brown turkey featured on the dining room table among your mashed potatoes, green bean casserole, and maybe even some cranberry sauce. To achieve that golden brown bird, your house chef likely has a very specific roasting process. It goes in at a certain time and at a specific temperature, it is brined before and then basted every so often, etc. It is also likely that many factors go into the production of this formula: the bird’s weight, the cook’s roast preference, stuffed or unstuffed. Where was I going with this? Oh yeah – coffee. Like the turkey, roasting is responsible for much of what produces an exceptional (or terrible) cup of coffee. This process is constantly manipulated to bring out the very best in different types of beans from all over the world. It takes years of experience working with a coffee roaster to master the art. If your bean-reading capabilities are still lacking, you could ruin hundreds of pounds of coffee within a matter of seconds.
The chemical reaction that occurs during the roasting process transforms the coffee bean from the soft, green, grass-scented seed into the crunchy, brown, aromatic bean you are accustomed to grinding. After roasting, the beans are cooled to room temperature and are ready to be ground.
The degree to which they are roasted, however, is a totally different story. The “perfect roast” is a personal choice, like grilling a steak. If you enjoy bloody, red center- say ‘medium-rare,’ then you will likely believe it is a sin to order a well-done steak. However, if you prefer the charred smoky flavor that comes along with a “well-done” steak, you might look at a rare one and wonder how somebody could possibly enjoy meat that appears to have been cooked with a light bulb. These principles also apply to preferred coffee roast, and the dogma seems to be simple: “people like what they like.” Nobody is wrong about personal preferences.
As for the roast classifications themselves, there are four main categories:
Contrary to popular belief, lightly roasted coffee contains more caffeine on average than a dark roast. As the roasting process goes on, caffeine content decreases. Each roaster may have their own sacred names for their roasts of coffee, but some defined ones for lighter roasts include “Light City,” or “Half City.” Like a rare steak, lightly roasting coffee provides an opportunity to taste some of the most subtle characteristics that differentiate beans from various parts of the world. The darker you roast coffee, the less able you are to discern these subtle characteristics.
A “City Roast,” or medium-roast, describes a bean that is dark brown in color but has not quite yet started producing oil on its surface. It is widely suggested that a medium roast provides the ideal balance of flavor between the beans and the roasting process itself. In other words, a medium roast allows for the full-flavor potential within the beans to be released.
The medium-dark roasts, “Full City” roasts, describe when you can first see some oil on the surface of the beans. They appear are darker, and may provide a slightly bittersweet aftertaste when cupped. A roast like this is commonly preferred toward the end of the day, or after meals. During these times, your palate has likely experienced some wear and tear, providing you with an opportunity to enjoy a darker, bolder cup.
Dark roast coffee seems to have many more aliases than the other roasts. They are commonly referred to as “Continental, European, Espresso, Viennese, French,” and the list goes on. If you examine dark-roast beans, you will notice a consistent oily surface spread throughout the batch. Going along with the steak reference, you will always taste part of the roasting process itself by drinking a dark roast coffee. It will lack acidity, but provide smoky, charred flavors that many consumers are seeking.
After roasting, there is a gassing off period for coffee beans. This process can take anywhere from 1-10 days to complete, depending on roast color. Dark roasted beans take longer to gas off than lighter roasts. During this time, carbon dioxide and other trace gasses are released from the bean. If you’ve ever ground and brewed coffee fresh out of the roaster, you’ve likely experienced an overflow of grounds inside of the filter basket. This is caused by a reaction between the hot water and trace gasses within the coffee.