Does Light or Dark Roasted Coffee Have More Caffeine?
One of the most common questions we get is which type of coffee contains the most caffeine: light roast or dark roast? Some believe that roasting darker burns off caffeine. Others feel that because dark roasted coffee tastes a bit stronger, it means it has more caffeine.
So what is the answer to the million dollar caffeine question?
A study conducted by roaster and scientist Juliet Han (found here) determined that dark roasted coffee does tend to have more caffeine than light roasted coffee, but not for the reasons one might think. Using awesome scientific equipment like a high pressure liquid chromatography machine, Han found that the level of the roast does not change caffeine levels for an individual bean. If you were to roast a single green coffee bean, the caffeine level in that bean would not change the longer you roasted it.
So why is darker roasted coffee more caffeinated? The answer comes down to weight and density.
As coffee is roasted, moisture iin the bean is released. That’s why a pound of green coffee will yield around 15-20% less roasted coffee when it’s done. The dark roasted coffee is less dense than the light roasted coffee. Whether you are weighing out an exact 25 grams of coffee or simply using a scooper to eyeball it, because the dark roasted bean is less dense, this means you are using more beans in a dark roast versus a light roast. And since the caffeine levels of the bean do not change whether its light or dark, the caffeine level is determined by the number of beans you are using, which will be higher for dark roasted coffee. Interestingly, Han found that when you weigh your coffee versus using a scooper, the dark roasted coffee winds up containing 32% more caffeine than the light roasted coffee, compared to a 9% increase when using a scooper.
While dark roasted coffee contains more caffeine than a light roasted coffee, the ultimate amount of caffeine in the cup is not solely determined by roast level. The way you brew your coffee still matters, as does how you store it and where the coffee comes from. But all other aspects being equal, darker roasted coffee does tend to have more caffeine than lighter roasted coffee.
Once again, we can thank science (and a woman scientist) for solving one of life’s great mysteries!