What is the difference between light roast and dark roast caffeine content per variety?

There is a persistent myth that dark roast coffee has less caffeine because the roasting process 'burns it off.' In reality, caffeine is a highly stable alkaloid with a melting point of 238°C, which is well above the temperatures used in standard commercial roasting. While the roasting process does cause the bean to lose mass and moisture, the absolute amount of caffeine per bean remains nearly identical across roast levels. The perceived difference in caffeine content per variety is almost entirely due to the genetic makeup of the plant.

When comparing coffee variety vs. varietal, it is important to note that species like Coffea canephora (Robusta) naturally contain nearly double the caffeine of Coffea arabica. Within the Arabica species, specific varieties like Geisha or Bourbon may have slight variations in caffeine concentration, but these differences are dwarfed by the species-level gap. When you choose a coffee, the variety is the most reliable indicator of potential caffeine content, not the roast color.

In practice, the confusion often arises from how we measure coffee. If you measure by volume (scoops), a light roast bean is denser than a dark roast bean. Therefore, a scoop of light roast contains more beans by mass than a scoop of dark roast, potentially leading to a higher caffeine concentration in the cup. However, if you measure by weight (grams), the caffeine content per gram of coffee is remarkably consistent across roast levels.

For the health-conscious consumer, focusing on the variety is key. If you are looking for a specific caffeine experience, look for the species and variety listed on the bag. Whether you choose a light or dark roast is a matter of flavor preference, as the roasting process will not significantly alter the caffeine content provided by the specific coffee variety you have selected.