Oven-Roasted Coffee

Health and Safety Tip: You should only attempt this method if your kitchen is well-ventilated or if you have easy access to a closed circuit, self-contained breathing apparatus. Seriously. Smoke is a natural byproduct of the roasting process and you're going to have to deal with it somehow. Consider turning off your smoke detectors during the roast. Open all of the windows. Learn to love the intense smell of freshly-roasted coffee because it will stick with you much longer than the smoke does.

Time: How long do you want your coffee roast to take? I personally don't care. I want an even roast with minimal or no manual intervention. Using the bottom rack of my oven results in the most even roast at a temperature range of 380 to 415 degrees Fahrenheit. For this demonstration, I've set the oven at 385F for two reasons. First, this extends the roasting time so I can easily show you the roast level over time. Second, I get the best consistency of roast at this temperature. Even if it takes a while, I don't have to stir the beans and I can wander off and do other things while I wait. If you are in a hurry, increase the temperature and stir as needed. Onward to the process!

Process Overview: I use a large baking pan. For the beans, I get 20-pound bags of coffee from Sweet Maria's. Different beans behave differently when roasted. I routinely get Costa Rican beans because I like the taste and I want to eliminate variables. This batch is tagged as Costa Rica Honey Palmichal Vecindario.

I preheat the oven and use the bottom rack. My oven has a convection bake option, which makes the temperature more even throughout the oven, but especially at the bottom rack level. A friend of mine has a very similar oven (Same brand, same production year), but he gets better results without convection and by placing his coffee on the middle rack. Ovens differ, so you may need to tweak the settings for your hardware.

At this temperature (385F), we have some waiting to do. I have some pictures below at 20 min through 45 min to show the gradual progression of the process. It is easier to see the progress if you zoom in on the pictures.

Start

20 min

Note how some of the beans on the edges appear to be roasting faster than beans further away from the walls of the pan. At higher temperatures, this effect is much more pronounced. At this heat level, it all evens out eventually.

30 min

40 min

45 min

Oven lights are not ideal for photography. Here is a picture of the beans cooling outside in natural light.

The chaff doesn't burn at this roast temperature, so it remains on the bean and I make no effort to remove it. I now have enough roasted coffee to service my caffeine addiction for several days!

Edit: I didn't mention how much coffee I roasted. I don't know. Usually I just dump beans on the tray until there are a lot of beans on the tray, but this time I measured 6 measured cups of green coffee with a pyrex measuring cup. That would be around 1440 grams if we were measuring liquids. After roasting, I put it in a bowl that with lines that indicate that I have about 12 cups of roasted beans. Lesson learned: my measuring tools suck and I need to get a scale.