Raw, unprocessed coffee beans contain caffeine. Every single one of them. Some varieties have more caffeine, and others have less, but the only way to drop the caffeine in brewed coffee to a modest 5-15 mg per cup is to take the caffeine out before the beans are roasted. Here is a quick summary of the main ways caffeine is taken from the bean, along with our highly opinionated thoughts about the best way to find a decaf coffee that tastes like coffee.
To take caffeine from a coffee bean, the first step is to soak or steam it to open its pores. After that, the process can go one of four ways.
The oldest and still most common decaffeination process uses a solvent to dissolve the caffeine from the coffee beans. The original solvent used was benzene (an unfortunate choice, since benzene causes cancer). The two solvents most often used today are dichloromethane (look for the initials, MC in a decaf coffee's name) and ethyl acetate (often called “natural” or “honey decaf”). The coffee beans are steamed and then soaked in the solvent, which dissolves the caffeine but leaves most of the flavor compounds in coffee alone. After hours of soaking, the beans are removed from the solvent and steamed again to remove the decaffeinating chemical.
In a second kind of decaffeination that uses solvents, the green coffee beans are first soaked in very hot water to remove both the caffeine and most of the flavor compounds. The flavorless, caffeine-free beans are discarded, and one of the decaffeination solvents is used to remove the caffeine from the remaining liquid. The solvent/caffeine is then evaporated off and the liquid is used to soak another batch of beans. After several cycles, the water and beans come to have the same chemical composition, except for the caffeine. At this point, only the caffeine is removed when the beans are soaked. Confusingly, these beans are sometimes sold as “water processed” decaf because the solvent shouldn't ever touch the green beans.
Swiss Water and Mountain Water Processes are a newer form of decaffeination that don't use any chemical solvent. Instead, the coffee beans are soaked in very hot water. The beans are soaked long enough to take out most if not all the caffeine and flavor compounds in the beans, creating what is sometimes referred to as a green coffee extract (GCE). The flavorless, caffeine-free beans are discarded, and the remaining liquid is passed through a carbon filter to remove the caffeine. The now caffeine-free liquid is reheated and used with another batch of green coffee. In theory, the process is repeated until the water is so saturated with flavor compounds that only the caffeine is removed. Coffees decaffeinated by these methods often have SWP, MWP or RSWP after the name, though some roasters shorten the initials to just WP.
The newest form of decaffeination uses CO2 gas. Water soaked beans are put into an “extraction vessel” that fills with high pressure, liquid CO2 gas. CO2 dissolves the caffeine, but not the flavor compounds in the coffee. Once the caffeine has been dissolved, the coffee is moved to another container, the pressure is released, the CO2 turns to gas and drifts off, leaving decaffeinated coffee beans behind.
All of these processes are safe. Many people worry about the process that soak the green coffee beans in a solvent, but the chemicals are very heat sensitive and even if traces are left after the second round of soaking, the high temperatures required for roasting the coffee flashes off almost all of it, more than enough to make the decaf safe to drink. Unfortunately, both MC and ethyl acetate leave a lingering flavor that some people can detect. While there are those who prefer the slightly fruity sweetness of ethyl acetate decaf, we prefer our decaf coffee to taste like coffee.
Producing decaf coffee that tastes like coffee is a challenge for all decaffeination methods. Every one of them require a form of “pre-brewing” that can mute the coffee's flavor. In our experience, the CO2 process affects a coffee's flavor less than any of the other methods. Unfortunately, the facilities are very expensive to build and need a high volume of business to make the process cost effective. As a result, most coffees used for CO2 decafs are of the lower quality, high quantity variety. Add to this that the CO2 decaffeination process is still under patent in Germany, and the result is very little Specialty Grade CO2 processed decaffeinated coffee is available in this country.
How do you make sure that your decaffeinated coffee will actually taste like coffee? The easiest and best way is to buy your decaf coffee from a coffee roaster you trust. Here's why:
A good roaster knows which companies only decaffeinate high quality green coffee beans.
It's tempting for a green coffee supplier to reserve its best green coffee beans for sale as regular coffee and to send lesser, and less expensive beans to be decaffeinated. Perhaps they feel that since the beans will lose some flavor anyway, it makes less difference in the brewed cup. They may even think that decaf coffee drinkers don't care about flavor. Our experience is that decaf coffee drinkers do care about the flavor in their cup and that decaffeinating the highest quality green coffee beans results in the highest quality brewed decaf coffee.
A good roaster will taste a sample of the decaffeinated beans before buying them.
Even starting with high quality green beans, the quality of the decaffeinated bean will vary. Some variation is due to the process, but even for roasters like us who only buy beans that have been processed without a solvent, the flavor varies. We've had water processed decafs that taste like hot, brown water, and others that taste like great coffee. We've had the best luck with MWP and RSWP decafs, but the only way to know for sure is to roast and taste the beans.
A good roaster knows how to roast decaf beans.
Decaffeinated coffee beans are more fragile than raw green beans. As a result, they roast differently, with decaf coffees going darker faster. They are much easier to over-roast, burning whatever flavor the decaffeination process left behind. If you've ever had a cup of decaf coffee that tasted like burned, brown water, that's why.
If you love coffee, but hate the caffeine, don't worry. There are delicious decaffeinated coffees out there. All you have to do is find a good roaster to steer you in the right direction.