It’s still not common knowledge that dark roast coffee is not, in fact, higher in caffeine content. It tastes strong and, often, that’s what matters to people. The science is conflicted as to just how much difference there is when it comes to caffeine content and roasting; but there are notable characteristic differences when you’re talking light, medium and dark roasts (and all those in between).
Roasting has the most significant impact on the flavor of your coffee. The naturally green seed from the coffee fruit plant is kind of soft, becoming brittle during the roasting process. It generally has a grass-like flavor or little flavor at all. Roasting releases sugars and other molecules (like caffeine, which contributes to the bitter flavor) which transform the color, texture, and flavor of coffee beans.
The most common coffee family is Arabica, which has lower caffeine content and therefore less bitterness than its counterpart, Robusta. It is only the risk-craving caffeinators that have started niche brands that market straight-up Robusta beans with such high caffeine content they’re barely legal in the United States. If Robusta is used, it’s generally for cheaper blends and dark roasts, because a darker roast already tends to be more bitter, masking the natural bitterness (again because of the caffeine) in Robusta beans.
The names for the different roasts intuitively come from the appearance of the beans: light, medium, and dark. There’s no roasting standard throughout the coffee industry, with most brands creating their own scale and labels. Most roasters generally roast within a similar range for light, medium and dark, however.
Light, as the name indicates, are lighter brown; they tend to have a lighter body when brewed, though Starbucks is one example where even the “blonde” roast is fairly dark for my taste. These beans are generally roasted for a short enough time that their internal oils do not have time to emerge, giving them a dry, almost matte appearance most of the time. A light, light roast, may taste more like toasted bread than chocolate, say and they tend to be higher in acidity than the darker roasts. Of course, elements like terroir and blending also have impacts on the overall flavor profile of a coffee. Typically, light roasts are used in specialty shops for single origins or blends with distinct flavor profiles; the lighter the roast, the more of the natural flavor profile the bean is likely to retain. As mentioned above, lighter roasts also tend to have higher caffeine content; although, how much higher is not certain and depends on several variables.
During the roasting process, light roasts are generally attained by removing the beans from the heat after the first “pop” or “crack” is heard.
The differences when it comes to medium roasts are fairly intuitive based on the above description. They are slightly darker than light roasts, therefore retaining somewhat less of the natural flavors as well as the caffeine. These roasts are more full bodied generally than light roasts (some of which can be so light they are almost like strong teas, for example). A medium roast generally does not have an oily surface. Mediums roasts also tend to have a more balanced, less dynamic flavor profile than light roasts, with a more balanced acidity as well. These tend to have somewhat less caffeine than light roasts and somewhat more than dark roasts; again, it is hard to say how much because of the lack of scientific review and roasting standardization.
Medium roasts are generally attained by roasting beyond the first “pop” or “crack” and up to right before the second one. If you’ve ever seen a coffee described as a “breakfast blend” it is most likely a medium roast by that brand’s standards.
There are medium-dark roasts and light-medium roasts, which fall in between the previous categories on the spectrum of characteristics.
Dark roasts are dark in color, often almost black, and generally oily or shiny because of the oils that have had time to release to the surface. They tend to be the most chocolatey and bitter in flavor and you’re likely to see the oils on the surface of the water when you brew a true dark roast. A dark roast is not one for a unique coffee bean or dynamic flavor profile, as the natural flavors tend to be roasted away and replaced with smoky, bitter, sometimes burnt flavors. Many people prefer dark roasts because they’re accustomed to a bolder coffee; this is likely at least somewhat held-over from cheaper, mass-produced coffee blends that used Robusta beans, as well as older brewing methods like percolators that would “strengthen” the flavor of the coffee over time. There is less caffeine in dark roasts generally.
Most dark roasts are roasted beyond the second “pop” or “crack”, though roasting much beyond that risks damaging the bean and resulting in a charcoal-like flavor. French Roast and Italian/Espresso Roast is often coded for a darker roasted coffee; though, it should be noted that espresso can be light, medium or dark as it refers primarily to the method of brewing and not the roast of the bean involved.
Later we will break down the roasts in more detail; but, this is a good, general starting guide. In the end, the roast is only the beginning of what contributes to coffee’s flavor profile. Even the amount of water used in brewing has an effect, as evidenced by the distinct taste of espresso which utilizes a pressurized small amount of coffee for brewing. That being said, learning that light roasts not only tend to taste better but have more caffeine completely changed the way I order coffee forever!
Make your arguments for the best (or worst) roasts in the comments below!