The process through which green coffee beans transform into the delicious flavored beans used to brew the coffee we love is known as coffee roasting. Although it is a fairly simple process, it is also quite easy to mess up. The overall concept is this: roasters use a source of heat to bring the internal temperature of a coffee bean high enough to caramelize its sugars and brown the bean from the outside, creating the overwhelming flavors of coffee beans that consumers have come to recognize.
The roasting formula, green coffee beans + right amount of heat + perfect amount of time = great roasted coffee, seems rather fool-proof. However, the guy in charge of mastering this formula has an important job, because even when the roasting process is run through machines, the success of the beans relies heavily upon his personal experience. Because he can only judge the process of the product based on his senses of sight and smell, the roaster must pay very close attention to the information he is receiving from the machine.
Heat, and how much the bean receives throughout different points of the roasting process, help to create the final flavors that sit in the cup that we drink. The heat plays a big role, helping to accentuate some flavors, hide others, and give characteristics to the beans. It creates the varying roast levels that all coffee consumers prefer. Generally, a light roast reaches an internal temperature of 350˚F to 400˚F, while a medium roast reaches 410˚F to 430˚F, and a dark roast climbs close to 465˚F.
The initial pea green color of the bean fades away as the chlorophyll breaks down, turning the bean yellow, then tan, before it begins the final process of turning brown. The bean will continue to turn deeper brown in color the longer it roasts, developing rich flavors as it continues to caramelize and vaporize its water.
While this process seems simple enough to understand, coffee roasters have an important job and must keep a watchful eye to help produce the final cup of coffee you have come to know and love.