It’s an unfounded assumption that dark roasts have a higher caffeine level than light roasts. But the opposite is true, with a caveat. In general, the rule is the lighter the roast, the higher the caffeine content. Surprised? You’re not alone. But here is the basic science behind it.
When a bean goes through the roasting process, it loses weight. So much so that an average roast will lose 15-18% of its original weight. That means, that if you roasted 454 grams of green coffee beans (1lb), the weight afterwards will only be 386 to 372.25g. That’s a significant amount of weight. Within that loss, there is a combination of moisture that gets evaporated as well as what we typically call chaff, and, yes, caffeine.
So when we talk about caffeine content in a roast, it’s important to know that the longer that beans are roasted, the more weight they are going to lose. So although a dark roast may be more robust and bold, it will typically carry less caffeine than that of a light roast.
Now is there a big difference in caffeine levels between dark and light roasts? Not as much as you would think. While it’s true that coffee will lose 15-18% of its weight during the roasting process, keep in mind that we are referring to green beans compared to roasted beans. There is a lot of chemistry that happens between green to brown beans (whether light or dark). So when we talk about a 15-18% loss in weight, the 4% loss between 15 to 18 isn’t a significant amount. Think about it like this: you have 100g of beans you are going to roast. After the roasting process, you are left with 82-85g of coffee ready to consume. That weight isn’t significant enough to make a huge difference when deciding how to start your morning (or keep your day going).
Now, I did say before that there is a caveat. Where you could find a significant difference in levels of caffeine is in the kind of bean that you going to roast or drink. The most common kind of bean that you will find on the shelf is called an Arabica. Arabica is simply a bean from a large, diverse, yet specific family of coffee plants. It typically has more of a pleasant taste, but usually costs more. The other major variety is called Robusta. It is very rare to find a bag of robusta beans sitting on the shelf at your grocery store. Most coffee snobs (and normal people for that matter) don’t just dislike robusta coffee but despise it. It is cheaper but less enjoyable. Robusta is typically used in instant coffee.
Another major difference between Arabica and Robusta is the caffeine content. While more enjoyable, Arabica coffee contains around 1.2 to 1.5% caffeine. On the other hand, Robusta, though less enjoyable and cheaper, averages around 2.2 to 2.7% caffeine content. So, if you want more of a jolt, Robusta is your best bet, though you will sacrifice flavor and quality.
Another caveat is how the coffee is prepared for consumption. Generally speaking, cold coffee is more concentrated and therefore has more caffeine. The caffeine amount will also depend on the ratio of water to coffee grounds. A lower ratio of water to coffee will result in more caffeine. The higher, the less.
So, do dark roasts have more caffeine? It depends. The science behind coffee is fascinating and will always amaze me. My hope is that you appreciate it more the next time you take a sip – regardless of the caffeine amount.
New Morning Mercies Coffee 