Decaffeination is the act of removing caffeine from coffee beans, cocoa, or tea leaves. Decaffeinated drinks still have around 1-2% of the original caffeine remaining in them. In the case of coffee, the process is usually performed on unroasted (green) beans, and starts with steaming of the beans. They are then rinsed with a solvent that extracts the caffeine while leaving the other essential chemicals in the coffee beans. The process is repeated anywhere from 8 to 12 times until it meets either the international standard of having removed 97% of the caffeine in the beans or the EU standard of having the beans 99.9% caffeine-free by mass.
The first commercially successful decaffeination process was invented by Ludwig Roselius and Karl Wimmer in 1903. It involved steaming coffee beans with a salt water solution and then using benzene as a solvent to remove the caffeine. Coffee decaffeinated this way was sold as Kaffee HAG in most of Europe, as Café Sanka in France and later as Sanka brand coffee in the U.S. Due to health concerns regarding benzene, this process is no longer used commercially and Coffee Hag and Sanka are produced using a different process. Coffee contains over 400 chemicals important to the taste and aroma of the final drink: it is therefore challenging to remove only caffeine while leaving the other chemicals at their original concentrations.
The Daily Omnivore 