There are plenty of places around the interwebs giving advice on how to roast coffee using a popcorn maker, but I thought I’d record my method here for posterity.
You will need:
- Hot air popcorn maker (see below)
- Green coffee beans
- An airtight container
- Two metal sieves or a flat baking-sheet sized metal mesh
- (Optional) A smaller metal mesh or strainer (see below)
The first thing to be aware of is that not all hot air popcorn makers are suitable. You need one with air vents around the sides (not at the bottom), and you need one that isn’t going to keep switching itself off when it gets too hot. This is hard to determine when you’re buying online, because the product marketing shots rarely show the inside vents and the product information doesn’t necessarily tell you about the thermal cut out. (I thought when mine arrived that I had got a wrong ‘un, but it turns out it’s fine.) The one you can buy in Lakeland is the right kind, but you’ll find cheaper online.
I first tried this a few years ago, when I was using a (manual) Gaggia machine and a separate grinder. When I moved over to various types of pod machines, I obviously stopped doing it, but then just over a year ago I got my bean-to-cup machine and it has been in my mind to do this again. Apart from anything else, I love the chocolate cake smell that fills the house when you’re roasting the beans.
There are various methods for home roasting. You could try a baking tray in the oven (but beware of smoke if you have smoke alarms). You can get a stovetop ceramic roaster, which looks interesting, but I don’t have the right kind of stove, and my barbecue with the gas ring on it is in France. I considered getting one and using my camping stove (and still might), but not for now. If you have the budget, you can buy a dedicated home roaster like this one, but they are really expensive.
I’m not doing this, by the way, for cheapness. I’m doing it for freshness. The crema of freshly roasted beans is about two to three times thicker than the crema you get when you buy beans in the supermarket. I don’t have a proper coffee roaster nearby. It was when a colleague gave me some beans he’d bought at the one near him that I decided to do it myself.
Second thing to be aware of: do not leave the plastic assembly on the top of the popcorn maker. It will melt. I’ve improvised a useful mesh cover (see above) by destroying a tempura strainer I had lying around in the kitchen drawer. This has two benefits: it stops the chaff that blows off the beans from flying around too much; and it stops stray beans from escaping from the machine.
I set mine up on a small table outside the house, with the power cable passing through the window. You still get the useful aroma in the house, but any chaff (and there will be chaff) blows away outside, and the machine can be aircooled a bit. Any smoke produced will also disperse outside rather than in.
You can only do a scoop of beans at a time. Use the scoop that comes with the popcorn machine. Prepare to do a few batches in a row, allowing the machine some cooling off time in between.
The expert sites will advise you to listen out for first and second crack. I find that this is an inexact science. I really base my decision on the colour of the beans and the chocolate cake smell. Also, when you stop the machine, if you leave the beans where they are, they will probably start to smoke (and potentially burn), which for me is a sign that they’re roasted enough.
You’re doing it yourself, so do what suits. If you like the modern tendency for more lightly roasted beans (with ‘fruity’ flavours), go for that. If, like me, you want a darker roast (but maybe not the blackest), then use your judgement and trial and error. I’ve found that 15-20 minutes in my machine gets the beans the colour I want, and the resulting coffee was, in the immortal words of Agent Dale Cooper, damn fine.
Once roasted for the requisite time, the beans have to be cooled rapidly. This is what the two sieves are for. Some people use a flat mesh screen: I guess if you’re DIY-minded, you could make one. The idea is to stop the beans from continuing to cook in their own residual heat, lest they burn. I pour from the popcorn maker into a sieve and then pass the beans from sieve to sieve until they are cooled. They don’t have to be cold. I say cool enough to put your hand in. Obviously wait until you try this, and don’t plunge your hand into scalding hot beans. If, like me, you have one sieve slightly bigger than the other, you can kind of sandwich the beans between them and use the smaller sieve to spread the beans around, rubbing away to remove any excess chaff. But simply pouring from sieve to sieve works just fine.
Note: when green, the beans smell like vegetation. Whilst roasting, you get a kind of cake-cooking-in-the-oven smell. They only start to smell like coffee about 20 minutes after the roast. When they’re cool, put them in an airtight container and leave them. I always wait a day: this gives the essential oils time to emerge and the coffee aromas to develop. You can lift the airtight lid after 20 minutes or so and you will smell coffee.
I got my green beans from Amazon. Rave coffee do a wide variety of green beans, so you can have hours of happy fun trying the various kinds. And when you’ve tried all the Rave, there are others to choose from, even on Amazon. They’re about a fiver (or less) a pack, and you can roast in small batches to keep the beans in your machine as fresh as possible. I’m sure you can find cheaper elsewhere, but the choice offered by Rave is clear and convenient. The label warns you to watch out for foreign objects (I assume stones), but I haven’t found any*.
This takes a little time, but if you’re in the business of making coffee from fresh beans, you’re not looking for instant gratification. The results are well worth it, and there’s nothing quite as satisfying as the first cup from a fresh batch.
*UPDATE: a few minutes after hitting Publish, I poured the very last batch into the popcorn machine, and there was a tiny white stone hiding at the bottom of the packet. So, one stone per pack. Also worth knowing: Rave offer a 4-pack sampler set of green beans on their own web site at a fairly decent price. They also suggest blending combinations, if you want to experiment with that.