Are there any other home-roasters in the community? I live in an area where the commercially available coffee tends to be pre-ground and stale. Over the years, I’ve started roasting my own coffee. Feel free to chime in to this post if you do the same or if you’re curious about it and we can compare notes on technique!
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.
Those are very long roast times I’d be concerned that you might see some over development which can cause the coffee to come out being more of a one note flavor with less depth and less acidity.
I’d like to hear your tasting notes on coffee you roasted with this process cause I’ve not experimented with longer roasts very much so I could be completely wrong.
Here’s a follow-up thought that you can take or leave. Having tried both head to head, I think that there is a flavor difference between what I do with my oven and a good high-temp low-time roast. Personally I think that the difference is minor, especially when you compare the flavor of either method to most of the coffee that you can buy from a grocery store. I suspect that the high-temp low-time issue is emphasized online because (if it is accepted as both true and important) it favors the purchase of specialty gadgets. Please try both and draw your own conclusions.
Thanks a bunch for sharing the perspective and experience I’ve thought this might be the case since I’ve discovered it to be the case in so many other areas of the coffee hobby so far.
I could be wrong, depending on your sense of taste. Once I cross the divide between bad coffee and good coffee, my ability to be a nuanced critic of flavor takes a nosedive.
I like how it turns out using this method, although I suspect that there might be some bean varieties where it wouldn’t work out. I tend to brew with a moka pot and the resulting cup has a delightful depth to it. You can cut the time considerably by raising the oven temp.
I generally don’t do that because I tend to get a less even roast and/or end up with a darker roast than I want due to inattention. If the human element in my equation were more reliable, I’d be roasting at well over 400F.