The Art and Science of Coffee Roasting
Many Factors Determine the Perfect Roast.
Coffee roasting involves cooking the whole coffee beans in a roasting machine to transform the physical and chemical properties of the green coffee beans in order to achieve the desired taste, or coffee roast types.
Coffee Roast Types range from light Cinnamon roasts to dark Espresso roasts, yet all coffee roasting caramelizes the carbohydrates and sugars in the coffee beans, changing them into the oils that give the coffee its taste and aroma. The longer a coffee is roasted, the darker it becomes and the less acidic it becomes. Coffee roasting makes green coffee beans expand and change color, also changing the taste, smell, and density of the beans.
A typical roasting machine is heated with propane gas and has an electrically-driven drum. Roasters operate at temperatures from 370 to 540° Fahrenheit (188 to 282° Celsius), typically around 400° Fahrenheit. Roasting machines keep the coffee beans moving, so the beans roast evenly. Hot air roasting machines are also known as “Fluid Bed Roasters” and roast the coffee by tumbling it on a bed of hot air. “Drum Machine Roasters” tumble the coffee in a rotating drum.
The Roasting Process
It may take about 15 minutes (12-30 minutes) to roast to roast 25 pounds of green coffee beans, depending upon how much coffee is being roasted, the temperature, the type of coffee, and a variety of other factors taken into account by the roastmaster (see below).
Light vs. Darker Roasts
Lighter roasts retain more of the gourmet coffee’s “origin flavors”—which are the natural flavors produced the climate and soil of the region where the coffee was grown, as well as the coffee plant variety. In darker roasts these origin flavors are eclipsed by the roasting process itself, with the roast flavor dominating the taste and masking the natural flavor of the beans.