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How do they make decaf? It's a simple question with a (relatively) simple answer, but you might be surprised to learn how decaffeinated coffee is made.

Big Questions is a weekly show where we endeavor to answer one of your big questions. This week, BekensDwarf asks: "How do they make decaf coffee when the caffeine is in the bean?"

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Hi, I'm Craig, my entire body smells of coffee when I'm out in the sun, and this is mental_floss on YouTube.

Today I'm going to answer BekensDwarf's big question. "Hey mental_floss, I have a strange question: how do they make decaf coffee when the caffeine is in the bean?"

That's not a strange question. What's a strange question is, Why would anyone drink decaf? But... I'll answer your question.


I want to begin by telling you about a 2006 study done at the University of Florida. Researches tested 10 16-oz. decaf coffees from 9 coffee shops. They found that 9 of the 10 cups contained between 8.6 mgs and 13.9 mgs of caffeine. And 0 mgs of purpose!

But that aside, this is still much less than a regular 8-oz. cup of coffee, which has about 85 mgs of caffeine. The only cup that didn't contain any caffeine was Instant Decaf Folger's Coffee Crystals. What am I telling you this? Well, I thought you should not that decaf coffee isn't always perfectly decaffeinated. If you're trying to go caffeine-free, be aware of what you're drinking.

Plus, it allows me to tell you without shocking you that the decaffeinating process doesn't remove 100% of caffeine from coffee beans. Usually, 94 to 98% is removed See? You're not shocked now, because I told you that thing.

So let's back up to before those decaf coffees were lying to unsuspecting consumers, when they were just little caffeinated beans. Before coffee beans are ripe, and are roasted, they are green. It's these green coffee beans that are used in the decaffeination process.

Before any other step, the beans are usually soaked in water or steamed, because it makes it easier for caffeine to be extracted. And the ideal temperature for decaffeination is 160 to 210º Fahrenheit. Oh, blah-di-dee-blah (71-99º) Celsius. I've... I'm not Canadian, I don't know.

There are a few different methods for decaffeinating coffee beans. One of these is called supercritical carbon dioxide decaffeination! Just felt it needed to be said like that. Green coffee beans are put in a pressure vessel with air pressure at about 250 times what we're used to. Carbon dioxide in the vessel is used as a solvent to remove the caffeine. A few hours later, the carbon dioxide, now containing the caffeine, is removed from the vessel.

Another way to decaffeinate coffee beans is the direct solvent method. Instead of using carbon dioxide to remove caffeine, a different solvent is used, like dichloromethane, or ethyl acetate. Basically, BekensDwarf, caffeine is in the bean, but we can use different solvents to remove the majority of that caffeine.

And here's a little historical background, so you can impress your friends: decaf coffee was invented by a German man named Ludwig Roselius in the early 1900s. He used the chemical compound benzine, not to be confused with my last name, on green coffee beans. In those days, benzine was also used in aftershave and paint. It turns out, benzine is not good for you.

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If you have a big question of your own that you'd like answered, leave it below in the comments. Thanks for watching mental_floss on YouTube, see you next week! Come on by to see what's... brewing! Hahaha! It probably won't have anything to do with coffee, though.