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Coffee roasting at home

September 28, 2009

The instigation

Frugal reader Mel wrote to us the other day about home coffee roasting. As it happens, this something I am totally into. I only buy commercially roasted coffee when the weather has prevented me from roasting on the weekend (it’s an outdoor activity using my technique) and the occasional bag to calibrate my taste and see what’s out there.

The maths

The economics are compelling. Green coffee beans of the highest quality can be had for about $14 a kilo, and acceptable ones for less. Compare this with roasted coffee which is usually at least $30 a kilo and often more than $40.

Green beans lose 10-20% of their weight when you roast them, but you’re still well ahead of roasted coffee for price, and better than a lot of commercial roasted coffee on quality. I’m afraid I have quite a bad coffee habit, more than 250g a week, so both the expense and the subsequent savings of home roasting definitely mount up over the year.

The results

I wouldn’t want to say that you can achieve the same consistent, refined results as a commercial blender without a lot of practice and some investment in kit. But you can definitely get something better than stale beans from the bulk bin at the supermarket or over-roasted grounds in a vacuum brick. If you do it every week, like I do, you can pretty soon achieve something that you like reliably. And that’s good enough, isn’t it?

(There’s also a lot of pottering fun to be had, but I realise this isn’t for everyone.)

My technique

I have blogged extensively about home roasting on my personal blog a while ago, before Frugal Me. Here’s how I do it.

I have a heat gun which I bought for $20 from Mitre 10. It is mounted on a drillpress ($12 from Trademe) with duct tape ($2 from $2 shop). The heat gun is aimed directly over one corner of the breadmachine mixing bowl. Conveniently, the bread machine lid is removable. Roasting coffee comprises a few simple steps:

  1. Set rig up on back step so that chaff and smoke will be blown away by the wind.
  2. Tip several hundred grams of green beans into bread maker pan.
  3. Put bread maker on “knead” cycle.
  4. Turn on heat gun.
  5. When beans reach desired roast level, turn off appliances.
  6. Remove pan, tip out beans, and cool (I put them in a metal pan in the freezer for 5 mins).

I drilled a hole in the bread machine pan and mounted a temperature probe ($15 from Trademe including digital multimeter readout) and I use this to gauge the progress of the roast.

So, for a total of $50 I have rigged up something that produces similar results to a much more expensive appliance, with far more possibilities for tweaking.

The whole thing takes about 20 minutes from the whim taking me to having beans cooling.

Other people use different methods: air popcorn poppers, an oven tray with the odd stir from a wooden spoon, or even a cast iron pan on the stove top.

The important thing is that you understand the coffee roasting process:

  1. Beans should be heated evenly somehow.
  2. Beans should be heated so that they get hotter and hotter.
  3. The beans will get darker and darker, until they start making sharp cracking noises and giving off a little smoke. This is called “First Crack”, and happens at somewhere between 180 and 200 degrees. Don’t stop here unless you like very acid coffee. The papery coating or chaff will start coming off the beans too. It makes a mess. Blow it off before you store the beans.
  4. The beans get darker yet. The sharp cracks stop, but after a few minutes a second, more gentle crackling starts — “Second Crack”. This happens somewhere after 220 degrees. Somewhere between this point and first crack is good for plunger and filter methods, somewhere close after this point they are ideal for espresso.
  5. French Roast or Starbucks level — almost black, not much of the bean variety’s characteristic flavour is left.
  6. Your beans are on fire.
  7. If you rescued your beans before stage 6, cool them with a fan or on a perforated metal sheet or however your ingenuity suggests. They will improve in the days after roasting, until a week or so, after which they get worse.

There are numerous online retailers for green beans these days. You can also try your luck at your local roastery — in Wellington, People’s Coffee and Havana have both been quite happy to sell me green beans at a reasonable price.

There’s a ton of information out there if you search for “roasting coffee at home”. However, I’ve found that some of it is pretty US-centric, and the Aussie Coffee Snobs site is a more reliable source for us.

Caveats

If you live in one of the larger NZ cities with good local roasters, the claims of marvellous quality that you read on the internet aren’t really true. Those people claiming home roasted is vastly better are usually Americans who live a deprived life, coffee-wise. On the other hand, if you live in the more rural parts of NZ, roasting your own from green is almost certainly better.

If you use a popcorn maker, or one of the other faster techniques, you end up with a brighter, more acid result that is usually too acid for espresso but delightful in plunger. Espresso roasts take longer, and need something like the breadmaker-based roaster.

Different brewing techniques suit different kinds of beans. Espresso in particular is often better with a blend, or at least a more “all-round” variety. For example, Ethiopian beans are aromatic and bright and acid and make for a potentially unpleasantly sharp shot on their own, but are nice mixed with Indonesian Mandheling beans. On the upside, you can make your own custom blend easily once you’ve experimented, which is an enjoyable process too.

You can burn yourself or electrocute yourself or set your house on fire once you start fooling round with roasters. Use your common sense.

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6 comments

  1. thanks for the info re the popcorn method Stephen, is useful for the plunger/espresso comparison


  2. Greatly enjoyed the beans you brought for Book Nite – many thanks 🙂 Of course, we had to buy a grinder, but then the following week J’s work were giving away free sacks of L’Affare beans ‘because they were a little stale’. J, who doesn’t drink coffee, scored 4 kg. Frugal WIN!


  3. Great summary – I’ve used the popcorn method with some success. It’s very dependent on the weight of beans you start with; if you play around you’ll find the magic weight for your popper that gives a good roast.

    I’ve also done several roasts stirring furiously with a stainless steel bowl and a heat gun, which allowed a larger mass of beans and gave more consistent results than the popper. Our old bread machine sits downstairs, waiting for me to rip into it and turn it to the dark (roast) side!


  4. From other articles I’ve read, it does appear best to do this outside. Yes, even if it does mean that the weather might dictate when you can do it.


  5. Great Stuff !!First time I heard of bread maker heat gun combo,missus would shoot me.
    I was stuck outside with an adapted bbq / Rotisserie ..thoughts of teatree smoked guatemalan.., anyway


  6. I couldn’t be bothered with the heat gun method. I’ve been using the popcorn maker for 3 years now and have perfect roasts every time. Only takes 4-5 minutes, depend on whether you go to the first crack or second, but this is an individual taste and you can roast precisely how you want to. Delicious



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