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Coffee Roasting

If there is any area of the "coffee culture" filled with as many myths, superstitions, half truths and holy grail searches as espresso perfection, it's got to be coffee roasting. Coffee roaster manufacturers go to a very great deal of trouble to produce modern, computer operated machines which can reproduce every aspect of a particular roast profile. A "profile" is actually a way of describing how much heat is applied to the beans, and for how long, at each stage of roasting. By changing and tweaking the roast profile, a master roaster can maximise the desirable flavours of the bean.

Except...if you buy the beans in a supermarket 6 months later, only the "base" flavour will remain, and not much of that. And even when they are fresh, 90% of the buying public won't be able to taste the difference. It's important to recognise that, while you CAN spoil a good coffee bean by roasting it badly, you can't improve a bad one by roasting it well. Roasting techniques are important, but ONLY if you are buying fresh coffee. If your daily cup is made from preground brick packed beans purchased in the supermarket, then all that matters is whether they've been roasted light, medium or dark.

In general, a light roast emphasises the acidity of the coffee, a medium roast develops sweetness, and a dark roast brings up the body. This presumes that these qualities are present in the bean to begin with, because many coffees lack some or all of these characteristics. The roast profile CAN influence this a bit; a fast roast will make the flavour "brighter" at the expense of some body, a slow roast will bring up the body at the cost of some front palate flavour.

Some people believe that there is an ideal roast for each bean, but in my experience this is only true for certain bean varieties. Kenya AA is a fabulous coffee at every level of roast from light to dark, but Yemeni Mocha only gives the true body, acidity and chocolate aftertaste when exactly correct. For many years Starbucks, building on the work of Alfred Peet, promoted an extremely dark "Full City" (?!) roast as being ideal, earning for their troubles the appellation of "Charbucks". Somewhere along the way they lost Peet's concentration on FLAVOUR and instead went for COLOUR. These days Starbucks have started to offer a variety of roast levels ("Lighter Notes"), but of course they are trying to promote the idea as if it's a new invention. This is generally known as marketing "spin."

The original coffee roasting apparatus is an iron pan with a well fitted lid, shaken vigourously over an open fire for 20 minutes or so. This is incredibly labour intensive and exhausting, especially considering that the amount of coffee involved is rarely more than 100g at a time. This is also probably the reason that home coffee roasting is "women's work" in Africa and the Middle East. If you ever try this method you soon learn why peaberries were prized; they roll around so easily that a great deal less shaking is needed to prevent burning the beans.

Bulk commercial coffee roasting simply enlarged on this, with a bigger "wok" shaped pan, more fire and more guys around it with shovels, furiously turning the beans. Around 1800 or so some bright spark came up with the idea of putting the coffee in a horizontal drum and rotating the drum over the fire; this is the basis of most modern roasters. The advent of electricity and electric fans has also resulted in "Fluid Bed" roasters, where the beans are suspended in heated air, but this is a relatively recent development. The "guys with shovels" concept is still widely used in Arabia and South East Asia, though these days the fire is usually gas.

Up until the mid 1800's most coffee was roasted at home, but after this large commercial ventures took over. An American viewpoint of these developments is available in Mark Pendergrast's book, Uncommon Grounds. Coffee went from a luxury to a commodity within 50 years, and home roasting virtually disappeared. However, the advent of the internet and the odd communities it creates has seen a resurgence in home roasting in the last half of the 1990's. The major nexus of this revolution is at, with Tom as its prophet; another one of the early converts was Ken David at, whose book has nurtured a new generation of home coffee roasters.

My personal favourite method for home roasting is using a popcorn popper, but these days there are a variety of specialist machines available (not QUITE as sophisticated as home breadmakers yet) which will do the job.

Alpenrost Roaster

Hearthware Roaster

Imex Roaster

Popcorn Popper

If you are eager to begin roasting your own coffee, I'd suggest that the first step would be an in-depth investigation of the two websites above. Home roasting isn't that hard, but you do need to pay attention, and you need to know a bit about the various stages that a coffee bean goes through during the roast. See for details, but the following is a rough guide.


1) If air temperature is below 15C, preheat the popper for 60 sec.

2) Add 80g of green coffee to popper.

3) Turn on popper and stir the beans in the general direction of airflow. You'll get covered in chaff, but never mind.

4) After 3 to 4 minutes the beans will start to pop like popcorn. This is known as "first crack."

5) The pops will continue for a couple of minutes, then stop. If you stop roasting at this point, you'll have a medium roast.

6) After another minute or so, a quieter popping/crackling will start. This is "second crack."

7)Stopping the roast at second crack will give you a basic dark roast. As you go longer into second crack, oil will appear on the beans and clouds of blue smoke will billow out, bean colour getting darker until the beans are black.

8) Whenever you stop the roast, tip the beans into a metal sieve, then toss back and forth into another sieve until they are cool enough to touch.


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