I like to usually compare roasting coffee to popping popcorn, but honestly that is a gross oversimplification. Roasting coffee is truly a more complex process than heating kernels of corn into delicious puffs of buttery goodness. And because I am not an expert in roasting I am going to link this informative article about coffee roasting basics by Counter Culture Coffee, one of the premier roasters and coffee educators in North America.
What I would like to briefly share is what tends to be a misunderstanding because of a lack of knowledge of the degrees of coffee roasts: light, medium, medium-dark, and dark. Dark roasts is where I will start because this degree of roast may carry more myths than any of the other roasts and shed light on the potential of the lighter roasts. For centuries coffee beans have been roasted dark, largely because people knew no other, but also because the roasting resources, like equipment and software, were not invented yet.
Today’s roasting equipment and software technology allows roasters to understand coffee roasting on a deeper level. Through scientific processes it was discovered that the coffee bean itself undergoes chemical changes that highly influence taste. It helped roasters to have greater control over roast time, temperature control, airflow, etc.
Dark roasts, if you will allow me to use the aforementioned primitive comparison, is similar to popping popcorn. The more you burn or char kernels of corn, the more it will lose its unique ‘corny’ flavor notes and develop a smokey or ashy tasting note. For example, there will be little difference between burnt buttery popcorn and burnt cheddar cheese popcorn. Coffee beans tend to react the same way. With a dark roast you can virtually bring similar tasting notes into play with two different beans simply by dark roasting them. Though there will be some flavor notes unique to the individual beans, they will have similar ashy or smokey notes because of being charred in the roaster. Dark roasts will also contain lesser amounts of caffeine and will be oily and shiny on the surface. By extending roasting time oils are brought to the bean’s surface that will create a bittersweet after-taste and give it a low acidic level and density. Also keep in mind dark roasts do not necessarily mean high heat, although it may.
In short, as we move on down the degree of roasts know that more caffeine is retained the lighter the roast is, it will be less bitter because less oil is roasted out of the coffee, and density typically increases as well. Acidity typically increases injecting different flavor notes. Keep in mind that too light will leave the coffee with a ‘baked’ taste similar to bread when it is under-baked. There are other factors that affect the end roast whether dark or light like how the coffee is farmed, the conditions of the terroir, elevation the coffee is grown, shade, etc. How they are processed also effects the taste of coffee; is it washed or natural. Additional influential factors during roasting will be; rate of rise, internal bean temp, time of first crack, potentially time of second crack, pyrolysis, etc. So it is a quite a bit more complex than popping popcorn, but hopefully you get the gist.
Bottom line there is no right or wrong in what degree coffee is roasted (Some may disagree with that statement depending on the desired end result.). No matter how much of a science or art roasting coffee is, the likability of a particular roast is ultimately held hostage by the subjectivity of a person’s taste buds. There are such things as negative flavor notes and positive flavor notes, and we can discuss that later, but again taste, with the help of the sense of smell, produces subjective results. Blessings!