We often get asked about decaf coffee. Questions range from ‘Is it any good?’ to ‘How do they decaffeinate coffee?’ The following is an attempt to explain a little bit more about decaf in general, and in particular about the decaf we use.
There are three main ways by which coffee is decaffeinated. The first method requires the use of a solvent, either methylene chloride or ethyl acetate. The beans are exposed to steam or hot water which makes them swell, after which they are soaked in the solvent. Both methylene chloride and ethyl acetate are selective compounds and they bond with the caffeine. Once the coffee has been removed from the solvent, steam is used to evaporate any residual solvent from the coffee. It is also possible to separate the caffeine and solvent, allowing the dried caffeine to be sold as a by-product.
While exposure to high levels of both these compounds can be harmful, the residual left in the coffee is around 1 part per million. It also appears that methylene chloride use is being reduced in favour of ethyl acetate. The term ‘solvent’ can have an air of negativity about it, but it is worth pointing out that ethyl acetate occurs naturally in wine. That said, we choose not to buy coffee decaffeinated by this process but instead rely on the other two methods.
Water processed decaffeination is undertaken in only two factories worldwide – in Mexico and Switzerland. Large amounts of coffee is soaked in water until all the solubles have been removed. This solution is passed through a carbon filter to remove the caffeine. The beans are then rehydrated in the green coffee extract and dried to their original moisture levels. This is a simplified explanation of the process and more information can be found using the links at the end. The caffeine cannot be recovered using this method as it would require the use of a solvent.
The following video from Swiss Water® shows this process in a lot more detail:
We’ve used a number of coffees decaffeinated using this method, notably those from Guatemala. As this process is only undertaken in two places, the added costs (both economic and environmental) of transporting the coffee can make it an unviable option. While producers in countries such as Guatemala can more easily transport their coffee to Mexico, those in Brazil, for example, will find it much harder.
This brings us onto the third method – the carbon dioxide process. Beans are soaked in hot water and are placed with carbon dioxide in a vessel where large amounts of pressure are applied. The carbon dioxide enters a super-critical state where it is partly a liquid and partly a gas. The carbon dioxide then attaches to the caffeine and the beans can be removed and dried. When the vessel is depressurised the carbon dioxide returns to a gas and releases the caffeine into the water. The carbon dioxide is reused and the caffeine is recovered from the water to be sold on.
Again we’ve often used coffees decaffeinated by this process. Coffees we receive from Brazil will have been decaffeinated in this way.
So is decaffeinated coffee any good? From my point of view I have been very happy with all the decafs we’ve used. I’m sure if I was able to compare the pre and post decaffeination coffees, side by side, I might be able to detect subtle differences. Caffeine brings acidity to the cup, for example, so by removing the caffeine you are reducing the potential acidity in the coffee.
We always aim to buy good quality coffee beans from distinct farms/regions. Even if the methods outlined above have a minor impact on quality, we would hope the resulting coffee is still good. Many people have no option but to avoid caffeine, for others it’s a lifestyle choice. Either way we feel quite strongly that we should provide a good quality decaf option for our customers. Who knows, as we grow in the coming years, we might be in a position to offer a wider choice of decaf coffees.
Sources and further reading: