Do light or dark roasts have more caffeine?
I was recently asked by a Twitter follower “why does dark roast coffee have more caffeine?”.

A lot of people believe that just because the beans were roasted dark and have a burnt taste, that means that the coffee is “stronger” and has more caffeine… but that isn’t exactly the case.

The quick answer is that for the most part, lighter roasts actually have more caffeine than darker roasts. When coffee beans are roasted, the beans undergo a series of physical changes including growing in size, becoming lighter in weight but also burning off some caffeine. The longer the beans are roasted (the darker the beans), in general, the less caffeine they will have solely due to them having more and more caffeine being burned off.

Now, it does get a bit more complicated than that. I mentioned that the longer coffee beans are roasted, the lighter they become (weight loss) so a pound of lightly roasted coffee could potentially have about the same caffeine content as a pound of dark roast (for example, a french roast coffee), simply because it would take more beans of a dark roast (going by weight) to make a pound. But, in general, taking 2 pounds of the exact same coffee – roasting one pound lightly and one dark – and not adding more beans to the darker roast to account for the weight loss due to roasting longer – the lighter roast will usually have more caffeine.

What kind of coffee beans have more caffeine?
In my blog post on Arabica vs. Robusta coffee beans, I noted that Robusta beans have a higher caffeine content than Arabica beans (about twice as much!). The downside, though, is that Robusta beans taste pretty awful. They are used by some roasters in coffee blends, sometimes as filler and sometimes for espresso blends solely due to their caffeine content. Since Arabica beans are associated with higher quality and better taste, Arabica is what you’ll likely find in your neighborhood coffee house or offered by a premium coffee roaster.

Which has more caffeine, espresso or drip brew coffee?
While on the topic of espresso, it’s important to note that, not only do dark roasts generally have less caffeine than light roasts, but espresso also has a lower caffeine content than drip brew! The reason is the length of time that the coffee beans are in contact with water for extraction. With espresso, the coffee may be in contact with water for 25 seconds or so. When making coffee via a drip-brew method, or even in a french press, coffee is in contact with water for a much longer period (up to 4 minutes). The extended time of the coffee being in contact with hot water is what allows more of the caffeine to make its way into your cup.

So the next time you want that caffeine “buzz” think twice before ordering that espresso or dark, french roast… and consider trying a lighter roast drip-brew or french press instead.

Please leave your comments below so we can continue the discussion and share this post with someone who enjoys good coffee. -Ken

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