You might be surprised to learn that the way a coffee is roasted can have a huge impact on the flavor. And we’re not talking about air roasting versus drum roasting, or home roasting versus commercial–different roasting styles that influence coffee flavor can be performed on any roasting equipment. Roasting coffee is as much an art as it is a craft, and one of the important variables that a master roaster has at their disposal is the application of heat. Or more specifically, how quickly or slowly to allow coffee beans to absorb heat.
Coffee beans are tiny chemistry labs. They start with a basic set of sugars, proteins and lipids sealed inside an airtight chamber that break down and recombine in myriad ways to create the tastes and aromas we experience as a coffee beverage. The magic ingredients that launch this parade of change is heat and pressure.
Coffee roasting machinery is designed to apply heat in a couple different ways. One is through direct contact with a hot surface, and the other is through contact with heated air. When coffee is roasted, it is taken from room temperature to around 400°F or more in a matter of minutes. A seasoned roastmaster knows that by applying the right amount of heat quickly at the beginning of the roast will kick off the chemical process without scorching the shell (which would taste bad). Also, knowing when to pull back on the heat is equally important. Once the chemical process begins at around 5 minutes into the roasting process, the rate of heat progression will cause some chemicals to recombine to create new flavors, while others are burned off and removed from the chemical equation.
Apply heat slower, more chemical complexity. Apply heat faster, preserve some qualities of the precursor chemicals. If you want a coffee to taste bright, clean, and sweet, a faster development and early finish are more likely to create those qualities. If instead you want the sense of smooth, rich, and robust flavor a slower development and longer roast is perhaps in order. And this does not apply only to light-roasted coffees. A coffee can have a lighter roast, but a longer development, placing it somewhere between the bright acidity of a light, fast roast and the cocoa-caramelized flavors of a dark roast. Also, it’s worth noting that heat can be applied too slowly, preventing the build up of pressure, and resulting in a lack of flavor development.
Oftentimes, the resulting flavor of a coffee is based on the preferences of the person who does the roasting, which is why the exact same coffee from different roasting companies can taste quite different. It’s also impossible to predict exactly how a coffee is going to taste based on a roasting style without some amount of experimenting. Each variety of coffee, each growing region, and each growing season all contribute to the chemicals that end up inside the coffee seed. Roasting cannot add anything new, it only works with what is already inside the bean.
As a coffee consumer, it’s a good idea to try coffees roasted with different styles, to find out what you like. And don’t be afraid to share your preferences with your roaster, so they can guide you toward coffees that you are more likely to be interested in. At Evansville Coffee Company, we approach each new coffee by roasting several different ways, and we will often come up with a light roast and a medium or dark roast for the same coffee, so that our customers can enjoy the range of flavors available in each coffee.