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 Most of us do not know where coffee comes from, let alone the process that enables us to partake of this wonderful beverage. Well, coffee must undergo several steps before we can drink it. Once in our shop we open the 132 or 154 pound sacks that reveal green, unroasted coffee beans. That's where our machine comes into play.
Ours is a Diedrich IR-7 which is a gas-fired, drum machine capable of roasting small batches of beans - up to 12 pounds. The green, unroasted beans go in the hopper at the top, then into the rotating drum where they are roasted, beginning at 360F and several minutes pass as we adjust gas pressure and air flow. The whole time they are roasting the beans are turning colors from green to yellow and then to different shades of brown. About 11-12 minutes into the roasting process we hear cracking noises begin. This is bean moisture which escapes the beans when they reach 380-395F. A couple minutes later we hear another set of cracking sounds which is carbon escaping the beans. This is about the time we're checking the beans every five seconds to check bean color, smell and skin development. When we think we've hit our mark- usually about 435F for a medium coffee or 460F for light to medium French, we dump the beans into a cooling tray.  The beans are then cooled over the next few minutes in order to stop the roasting process.
Depending on what we're shooting for, the roasting process can take anywhere from 14 1/2 to 17 minutes, besides the cooling time. What's really happening in the roasting process is that flavor oils are being developed over the course of a carefully followed time/temperature profile. The oils are what flavors the hot water that we enjoy as coffee.
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