Why?
Even though green coffee beans tend to be heavier due to the higher water content, generally itās cheaper to roast your own compared to buying them pre-roasted.
You can roast the same beans at different levels to get some variety without having to go out and buy a new batch.
Itās kind of fun and a decent conversation topic.
Notes
Donāt be scared by how long this post is. It basically just comes down to spread beans on a cookie sheet, put in preheated oven, wait around 12-15 minutes and then take them out and cool them.
Since weāre talking about roasting beans, naturally youāre going to need a grinder to actually use them.
The process will create some smoke, even with a light roast. Basically, darker roast, more smoke. So far Iāve mainly done pretty light roasts and even though my kitchen doesnāt have much ventilation (and my oven doesnāt have fancy modern contraptions like, you know, a light or a fan) it hasnāt been an issue.
Your oven should be reasonably clean if you donāt want the roasted coffee to taste like random stuff.
If youāre a super coffee snob and it has to be perfect, this may not be for you. Itās pretty easy, but odds are the first few tries arenāt going to be perfect especially if you like darker roasts.
Youāre going to want something like a large metal mixing bowl and colander for the cooling process. My colander is plastic, so you can probably get away with that if you donāt put the red hot beans in it directly out of the oven.
Youāll also probably need access to an outside area where bits of coffee chaff blowing around arenāt going to bother people. I donāt think thereās really an easy way to deal with coffee chaff indoors.
By the way, donāt try to grind green coffee beans in a normal grinder. They are insanely, and I mean insanely hard and tough. Youāll destroy your grinder unless it is an absolute tank. (Iād say itās also not really worth trying, green coffee didnāt taste very good to me.)
How
Hereās the process:
- Start preheating your oven to 500f/260c. (Some people say as hot as possible, some people use a slightly lower temperature like 460-475f.)
- Get a cookie sheet ready. Just a standard cookie sheet. Mine arenāt super clean so I put a layer of silver foil on it. Donāt preheat the cookie sheet itself.
- Measure out about 1 cup of green coffee beans. (Iāve found you can fit about 2 cups on a single sheet but itās probably better to start small.) You want to make sure the beans are spread out evenly in a single layer.
- Look for beans that are discolored/damaged and toss them away. Donāt be a perfectionist though, just get rid of 10-15 of the worst looking beans. Something like that.
- Place the cookie sheet in the oven once itās reached the correct temperature. I put mine on the bottom rack near the (electric) heating element. If youāre going for a darker roast, I guess this might make burning them more likely.
- Set a timer for ~12 minutes. I wouldnāt recommend roasting longer than 14 minutes your first time.
- Now you wait a bit. Probably around the 8 minute mark, youāre going to start hearing sharp cracking/popping sounds. Donāt worry, the beans wonāt jump around like popcorn and the sound is fairly loud so youāre not likely to miss it. At this point (or in 1-2 minutes) you can remove the beans and have a light roast. This point is known as the āfirst crackā.
- After a couple of minutes, the sounds will die off and you wonāt hear anything for a little bit. If you keep roasting, youāll start to hear a softer, more muted crackling sound start. This is the āsecond crackā. I would not recommend roasting past this point until youāre comfortable with the process and have an idea of how roasted the beans are at this point. If you roast much longer, itās very easy to burn them and thereās also going to be a lot more smoke.
- Remove the beans from the oven. You can let them rest for 1-2 minutes on the cookie sheet if you want, then transfer to something like a metal mixing bowl. It has to be something that can deal with 500f stuff touching its surface.
- Ideally get another mixing bowl/colander/whatever as well. Pouring the beans back and forth through the air is a good way to cool them off and remove chaff. Whatās chaff you ask? The beans are coated with a papery layer of chaff. Donāt worry though, once theyāre roasted itās really easy to remove. You want to try to cool off the beans pretty quickly at this point.
- Go outside and blow gently on the roasted beans in your bowl. You should see a bunch of super light, papery chaff fly out. You can pour the hot beans from one bowl to another, and if thereās a bit of a breeze thatāll help a lot. Otherwise, you can just blow on them. You could also stir them around with a wooden spoon or something to encourage the chaff to separate.
- Once the chaff is mostly gone (itās fine if thereās a little left, or little pieces stuck to some beans) and the beans are fairly cool you can just leave them in a safe place for around 12 hours to fully cool and vent CO2. Donāt put them in a sealed container for the first 12-ish hours.
Conclusion
One thing to note is you donāt want to actually grind/use the beans for at least 12 hours. It might seem unintuitive, but from what Iāve read as freshly roasted as possible isnāt necessarily best. Depending on the beans/roast level, the coffee might reach its optimal tastiness even a couple weeks after roasting.
Iām far from an expert, but feel free to ask questions in the comments if you want. I can recommend a grinder/beans to get started with if anyone needs information like that.
Yes I used to roast at home several times a week on a Behmor machine. Thereās a reason all the at-home machines (and commercial machines for that matter) have smoke suppressionā¦
Edit to add that I started with a popcorn popper (which is the usual entry into the hobby) then built a roaster out of a heat gun and a flour sifter before I went on to get the Behmor. All of my roasting was done outside or in the garage with fume hood and exhaust fan.
Do whatever you like but thereās a reason there are things like occupational safety regulations and the like.
Did you try other methods like oven roasting them though? If not, it may be hard to compare.
Well sure, obviously itās a useful feature. The fact that a feature exists doesnāt mean itās absolutely necessary and you canāt live without it, though.
Also, like I mentioned, darker roasts are going to produce more smoke. A lot of people do like dark roasts. I advised using a light or medium roast in my initial post though. Basically, people can try it out and experiment, see what levels of smoke/etc theyāre comfortable with. Maybe theyāll find that their preferred roast level produces too much smoke ā thatās certainly possible. Someone who wants to give it a shot doesnāt have to commit to roasting their own coffee for the rest of their life.
I remember the inventor of the Behmor machine saying that the smoke suppression was required by regulation of some sortā¦ ao yeah they are kinda necessary in a sense.
Like I said, do whatever you like, but I advise against roasting coffee indoors without an exhaust fan that dumps the exhaust outside, at minimum.
They say technically correct is the best kind of correct!
A coffee roasting machine has to be able to handle basically whatever people do with it: dark roasts, light roasts, small enclosed spaces, whatever.
I just havenāt seen enough smoke to be concerned. Maybe my experience is abnormal, I donāt know. Itās not even like the oven was full of super dense smoke or anything, but keep in mind the only smoke thatās really going to come out is what drifts out naturally for the < 10 minutes the beans are roasting and the 10 seconds the oven door is open.
Now if youāre roasting well past the second crack then certainly that might change things but I usually prefer pretty light roasts. I took my current batch out right at the beginning of the first crack. There was virtually no smoke at all. Of course, you too should do what you like: though Iād respectfully suggest that maybe you shouldnāt be super confident about the effects if you havenāt actually tried this approach yourself.