Roasting Mechanics 101

Like most worthy endeavors, roasting coffee is an art honed over time. The basics of roasting are fairly simple, much more so than most people realize. In their raw state, coffee beans are hard, green and slightly chewy. As they roast, the begin to turn brown and expand, releasing their water content and opening up at the cellular level. They begin to crack and pop as they continue to expand and gas trapped inside the beans escapes. At this point, the beans become exothermic, generating their own heat, rapidly pushing up their internal temperatures. If the beans are allowed to continue heating up, eventually flavor oils will be forced out on to the surface of the beans and they will begin to caramelize, then burn.

Ideally, roasting equipment should enable the beans to progress through this process evenly and consistently, so that the beans all roast about the same rate and the roastmaster has predictability between roasts. Ideally. Since my roaster is home-made, it lacks some of the perks of professional roasting equipment, such a sample port that allows you to take out a few beans without interrupting the roast or a built in cooling pan that allows a rapid a transfer of the beans. However, because it is home-made, I also have the ability to upgrade it as my skills progress and my understanding of the elements of a good roast evolve. So, with a couple of weeks off from the markets, I have taken some time to rig a new and stronger motor that will turn the drum faster and more evenly. This should not only increase the consistency of my roasts but also the speed. But only time will tell.