Ready to bust some myths? Roasting doesn't affect caffeine. I'll repeat that - roasting doesn't affect caffeine. So why does urban myth insist that darker roasts have more caffeine?
Well, lets look at the truths we know:
1. Each individual coffee bean has the same amount of caffeine.
2. Roasting removes moisture from the bean. Darker roasts are taken to a higher temperature, which removes more moisture from the beans.
3. Moisture is heavy. Darker beans have less moisture; they weigh less than lighter roasts.
4. If you measure your beans by weight when making coffee, you will use more beans from a darker roast than a lighter roast. More beans = more caffeine, hence the myth. However, if you measure your beans by scoops, it really doesn't make any difference.
5. Keep in mind these are VERY minor differences. A pound of the darkest roast has about 90 more beans than the lightest roast.
4. Only glitch in this - our first "truth" - each bean has the same amount of caffeine. This isn't actually true. Read more: Arabica vs. Robusta.