Light Roast Coffee vs. Dark Roast Coffee, Caffeine, and Sugar

This week we are diving into light and dark roasts. What’s the difference?  How does the roast affect taste? Does darker and stronger mean more caffeine? Find out the answer to these questions and more in this week’s Coffee Science.

The Dark Side. The Light Side.

Coffee is roasted on a scale from light to dark. A darker roasted bean is  roasted longer and is therefore darker in color, much like anything else when exposed to heat. With that in mind, a lighter roasted bean is just the opposite. You can think of an unroasted (“green”) bean as white bread, a light roasted bean as lightly toasted bread, and a dark roasted bean as a – well, you get the idea. When we’re talking about light and dark roasts, we’re just talking about how long the bean has been exposed to heat in the roasting process.

Of course, the color isn’t the only difference.

Flavor Profiles

The flavor of the coffee changes tremendously as it is roasted. In fact, as coffee is roasted its flavor profile moves further away from the bean’s natural characteristics. To better understand why this is, it’s helpful to know how a coffee bean obtains its flavors to begin with.

A bean is the pit of the coffee fruit, or cherry. As the cherry matures, the bean will absorb the sugars and flavors produced by the fruit. We discuss this a bit more in our previous article Coffee Science: What Does MASL Mean For You?.

As the bean is roasted, those sugars will burn off. This is an oversimplification, but that is the basic idea behind the taste differences. As a result, a lighter roast will tend to be sweeter and a darker roast will tend to be more bitter.

Caffeine Levels

There’s a bit of a misconception out there that a “stronger” (more bitter) cup of coffee contains more caffeine. This actually isn’t the case though the myth is founded in some truth. When we’re strictly talking about the C. arabica species of coffee and caffeine levels as correlated with roast level, *a lighter roast will always have more caffeine*. This is because the bean is exposed to heat for a shorter period of time, and as such less caffeine is burned out.

The story changes when we begin talking about the less favorable C. canephora or Robusta coffee. Robusta naturally contains more caffeine than C. arabica. This means that technically a darker roasted robusta could have more caffeine than a lighter roasted C. arabica.

Which do you want?

Well, if you drink coffee, chances are you already know which type of roast you prefer. If you regularly drink and enjoy Starbucks, you likely prefer darker roasts. If you regularly drink and enjoy your local cafe’s single origin Ethiopian or Costa Rican, you likely prefer lighter roasts. Whichever camp you’re in, there’s no losing. Just remember to try out the other side once in a while. You never know when your tastes might evolve!