How is caffeine extracted from whole coffee beans?

Chris - I have to say until he raised the question, I haven't even considered it but it's a very good question.Kat - It is. I am a decaf coffee drinker. I'm caffeine-free so this actually intrigued me as well. In fact, there's a number of different ways that people get the caffeine out of coffee. They do it on the whole beans. It's not when you brew up the coffee and then take the caffeine out of it. You decaffeinate the beans before they're even roasted because that helps preserve as much flavour as possible when they're finally roasted and then ground up. So, there's a number of ways you can do it. You can do it the nasty way, which is to bung a load of solvents in there. Caffeine dissolves in certain solvents, some of the ones kind of slightly related to things like dry cleaning fluid (not very nice way of treating a coffee). So people try and develop other ways of doing it with things like water. You can basically just try and wash the caffeine out by washing the beans and then filter out the the caffeine. There's another really clever way that people do it is by washing the coffee beans with a very, very strong solution of coffee that's sort of saturated with all the coffee flavour molecules.Chris Smith: But presumably decaf.Kat - But not caffeine.Chris Smith: Right.Kat - So, basically it's using, I guess it's osmosis isn't it, sort of. Chris Smith: Diffusion. It's the diffusion gradient.Kat - That's the one.Chris Smith: If there's no caffeine in the solution and there's lots of caffeine in the bean there'll be a net movement into the solution.Kat - Exactly, the caffeine goes out the beans into this coffee-flavoured solution, but you don't lose any of the flavour from the beans because there's already loads of these flavour molecules in the water so they don't want to move out of the beans. That's another way of doing it using carbon dioxide as well, high-pressure carbon dioxide which kind of forces the caffeine out without losing the flavour. So, that is apparently how they do it.