Mental Floss recently posted a video answering a user-submitted question, “How do they make decaf coffee when the caffeine is in the bean?”
Craig Benzine, “host/coffee connoisseur,” describes a method for decaffeinating coffee called “supercritical carbon dioxide decaffeination,” where green coffee beans are put in a pressure vessel and carbon dioxide is used as a solvent to remove the caffeine. He also mentions the direct solvent method, where instead of using carbon dioxide to remove caffeine, a different solvent is used, like dichloromethane or ethyl acetate.
This is an interesting snapshot of decaf processes, but there’s a method of decaffeination that Benzine didn’t mention–the “water process”. Here, Emma Sage, Coffee Science Manager at SCAA outlines the process:
First, with all this talk of decaffeination, it is important to remember that for adults who consume moderate levels of coffee a day, most scientific literature concludes very little health risks and even some health benefits from coffee drinking. There is even growing evidence which links caffeine to coffees potential health benefits. That being said, if decaf is your preference, you should know that U.S. Federal regulations require that coffee must have had its caffeine level reduced by no less than 97.5 percent in order to be labeled as decaffeinated. Also, know that decaf is safe – no matter what method is used. The U.S. FDA has approved chemical decaffeination solvents (methylene chloride and ethyl acetate) as long as they are removed so the final residue not to exceed 10 parts per million (0.001 percent) in decaffeinated roasted coffee. So, enjoy your decaf any way you choose!
There is a third method to decaffeinate coffee, and that is via the “water process”. Caffeine is water soluble, but it turns out that many other compounds are as well, some of which might contribute to coffee flavor and we would rather keep in our coffee. Therefore a process has been developed where green coffee extract (minus the caffeine), is added to hot water and used to soak green coffee seeds in order to extract only the caffeine through osmosis. Since there is zero caffeine in the water and coffee extract solution, this means that the caffeine is drawn out of the coffee seeds due to a concentration gradient. The solution is then filtered to remove the caffeine, and the coffee is soaked again. The coffee can be soaked a few times in order to eliminate caffeine but keep as many of the other flavor-influencing compounds in the coffee seeds as possible.
Interested in learning more about caffeine and why it varies among cups of coffee? Read Sage’s article: Ask Emma: Should I worry about over-caffeinating anyone?
To learn more about the water process of decaffeination, check out this informational video by Swiss Water.