Home Coffee Roasting 101: Intro
It's been a long trip from the Folgers of my early days to the heights of coffee snobbery at which I now find myself. It started by discovering Dunkin Donuts coffee. At some point I learned how much better it was if you ground the beans yourself, and switched to whole beans. Then, brewing methods -- French Press, vacuum-driven coffee makers, eventually coming back to the drip coffeemaker and settling on the best of the best. Without question, the biggest improvement in my coffee has come from learning to roast. It takes a little practice, but even your mistakes will be drinkable. Once you hit your stride, you will be delighted with every morning cup.
First, the science: We need to heat the beans. As the internal bean temperature passes around 350, the water inside boils and the steam forces its way violently out of the bean, creating a loud crack. The chorus of cracks (collectively called the "first crack") signals the onset of pyrolysis, where the insides of the bean begin to caramelize. Caffeine begins to burn off as the temperature passes 350 (no worries, there'll be plenty left.) It's around 400 that enough of the raw bitterness is gone that the bean could produce a drinkable cup of coffee. When the internal temperature hits about 440, the woody cellular structure begins to char. This shrinks the bean, releases the coffee oils (resulting in a shiny, oily bean) and produces a bittersweet roasted flavor. When this happens, a lighter, thinner crackle is heard, which is called the "second crack."
When the bean passes 500 degrees, if you expose it to air, it will catch fire. Obviously you don't want to take it this far. The darkest roasts stop in the mid-460s.
There are four main variables to control. The amount of coffee roasted, the identity of the coffee, the temperature of the roasting chamber, and the time of the roast.
There are a number of devices that can be used for the roast. You can use your kitchen oven, if it'll get hot enough (550). You can also use a popcorn popper -- either the stovetop type with the crank handle, or the hot air type. I've been using a Fresh Roast Plus Eight coffee roaster, which can be found commonly enough for around $90. The Nesco roaster at $160 comes pretty highly recommended. Both the Fresh Roast and the Nesco do about one coffeepot's worth per batch. You can spend a HELL of a lot more than that, pretty easily. Higher end roasters allow a lot of control over the variables, so you could bring the beans up to 375 and park them for a few minutes, then continue the upward march.
It's important to keep the beans moving rapidly throughout the roast. This helps keep the roast even. Commercial roasters all do this for you, of course. (With the kitchen oven method you just shake the pan every once in a while and live with the less even results.)
You can obtain green coffee from your local roaster. Some homebrew shops carry it as well. When you get the hang of it, you'll probably do like me and order a 55lb burlap sack of green beans over the 'net. (I'm drinking Colombian every morning for around $4 per lb.) You can read a lot about coffee varieties with a few quick searches.
Roasting makes a lot of smoke, so prepare for it. If it's nice weather, roast outside. If not, use the stove hood's vent fan, open a door, and use a box fan to draw air out.
My Fresh Roast roaster is an extremely fast roaster. From start to first crack takes about four minutes, and the second crack usually starts at about the six and a half minute mark. I pull the beans as soon as I hear the first ten or so cracks of the second crack. This is a very fast roast, and does not really let the flavor develop. On the other hand, if it goes too long, like thirty minutes, you're not roasting the coffee, you're baking it. Your coffee will taste stale and woody. I think fifteen minutes to the second crack would be about ideal. Counterintuitively, the roast takes longer if there are fewer beans.
When they're done, you should cool them as fast as possible. I dump them into a thin aluminum cookie tray, which absorbs and disperses the heat very quickly. Another common trick is to decisively kick off the cooling process by spraying three or four "mist" shots of water from a sprayer onto the hot beans while tossing them in a colander. Most commercial roasters include a cooling mechanism.
The beans should be allowed to sit a couple hours at least. They're best after around twelve hours as the CO2 leaves the beans. At this point you should either use them, or move them to a sealed container. They'll begin to lose their flavor immediately, but will still taste pretty awesome after 10 days or so.
This subject could go on and on about blends and all sorts of things, but I'll leave it here. There may be later articles!