DECAF COFFEE: A SHORT INTRODUCTION
Decaffeinated coffee, it’s safe to say, has a bit of an image problem. It’s either being openly belittled, the butt of a bad joke (“There’s a time and a place for decaf: never and in the trash” is a classic) or is otherwise ignored entirely. And it’s easy to see why – the majority of people drink coffee for the caffeine, so decaf seems to them completely pointless. Plus it usually doesn’t taste all that good.
In the specialty coffee world it isn’t taken much more seriously – it’s usually an afterthought at best, something to keep people with caffeine intolerances happy. But it’s still there, sitting patiently, slowly going stale, waiting for someone to drink it. And actually, it’s more popular than you might think: around 12% of global coffee consumption is decaf. So it’s worth asking (and most baristas and roasters will have been asked this question about a thousand times) – what is decaf coffee, anyway? How is it made? And is it possible to find a good one?
The first thing to note is that decaf coffee is not completely caffeine-free. The EU demands that 99.9% of caffeine is removed from anything labeled decaf, whereas the US is slightly less strict, insisting that it is 97% caffeine-free. Is this interesting? Who knows. Anyway, onwards.
The first commercialised way to remove the caffeine from coffee was discovered in 1903 by the German merchant Ludwig Roselius, when his coffee shipment was accidentally soaked in sea water, removing much of the caffeine without completely ruining the taste. He later used benzene as a solvent to remove the caffeine, although as benzene became known as a carcinogen its use was phased out in favour of other, less harmful chemicals. Otherwise, Roselius’ approach has formed the basis for the majority of decaffeination techniques in use today. Here are the main methods:
Direct Solvent Method
In this method, the green beans are soaked in water to open up their pores and then repeatedly rinsed in a solvent, usually either dichloromethane (methylene chloride) or ethyl acetate, to remove the caffeine. The solvent is then evaporated and the beans rinsed in water to remove as much of the chemical as possible – roasting gets rid of the rest. This process can be repeated numerous times to achieve the preferred level of decaffeination.
There is also the Indirect Solvent Method, in which the coffee beans are soaked in hot water for several hours, then are removed and one of the above solvents is used to remove the caffeine from the water, and the beans are reintroduced in order to absorb the flavours and oils from the now-caffeine-free water.
One thing to note: new research has found that dichloromethane, a substance also used to make paint thinner, contributes to the ruination of the ozone layer and generally is no good for the world at all. So you might want to take that into consideration next time you're choosing your caffeine-free brew.
Carbon Dioxide Process
This is similar to Direct Solvent, but uses carbon dioxide in place of the solvents. High pressure vessels are used to circulate carbon dioxide through pre-moistened green beans. At such pressures carbon dioxide becomes supercritical, enhancing its effectiveness as a solvent – it acts similarly to the chemicals noted above, dissolving and draws the caffeine from the beans. This method is considered safer due to the lack of chemicals used, but is so cost-intensive that it is generally only used for large-scale, low-quality, commercial grade coffee.
Probably the most well-known process, and the most popular in the specialty coffee world, is the Swiss Water Process. Invented in Switzerland in 1933 and , it uses Green Coffee Extract (GCE) and activated charcoal to remove the caffeine from water-soaked green beans. The beans are immersed in GCE, a liquid containing all of the flavour components of coffee but none of the caffeine, which extracts the caffeine from the beans. The decaffeinated beans are then removed and dried, while the caffeine-rich GCE is passed through activated charcoal filters to remove the caffeine. The solution is then re-used on the next batch of beans. This process is considered more natural, and is generally used for higher-end and organic coffee.
Decaf coffee is decidedly tricky to roast, being far less predictable than regular green coffee, and needing far closer attention. The results, flavour-wise, are often hit and miss. I have tasted a lot of mediocre decaf coffee, but occasionally you can find some that retains much, if not all, of the characteristics of regular coffee. Sometimes it can be truly excellent, but a lot of this is down to the skill of the individual roaster.
In the end, there are a lot of people for whom ingesting caffeine is a dangerous dance. Some are completely allergic; other’s just have a sensitivity. I’m actually one of those latter people – my coffee limit is two cups per day, or else I start to feel weird. So decaf has its place, it just needs to be taken a bit more seriously by roasters and perhaps approached with more care by baristas. It’s not the enemy, it’s just another drink.