Dark Roast Coffee Has Less Caffeine and Tastes Worse | Thank Us Later

This is a public service announcement. Sponsored by Just Blaze and the good folks at Roc-A-Fella Records. Fellow Americans, it is with the utmost pride and sincerity that we present the following:

Dark roast coffee has less caffeine and tastes worse than lighter roasts.

Now allow us to re-introduce ourselves:

Dark roast coffee has less caffeine and tastes worse than lighter roasts.

If you were not aware of this, do not worry, it is not your fault. In all honesty, it is something that we did not know until a few years ago. Not just that, we only learned it after visiting a coffee plantation on the outskirts of Medellin, Colombia. Even after that experience, we were still slightly skeptical.

Another year passed before we then encountered the same claim on a separate coffee farm in San Miguel, Guatemala. And even after that experience, we were still slightly skeptical.

And can you blame us? It challenged our previously held conventions about coffee and directly opposed what we understood to be true. However, we are always open to new information.

We are engineers, after all. Nothing is more engaging than solid science. So, naturally, at this point, we began researching scientific publications to get to the bottom of this.

If this seems like an abnormal way to learn about food, it’s because it probably is. You shouldn’t have to travel to the Andes mountains or re-activate your JSTOR account to determine the caffeine content in your cup of coffee. We want to provide an easier way.

That path starts by addressing the commonly held perception among coffee connoisseurs that stronger, more intense, and more flavorful coffee is produced by a dark roast. This belief also extends to the caffeine content as well with the dark roast allegedly yielding higher caffeine content compared to lighter roasts.

Ultimately, everything related to food and taste is subjective and includes some level of personal preference. However, when your barista’s palette may say one thing, science is here to offer another explanation. It’s the great thing about science. Whether or not you choose to believe it, it’s still happening.

To better understand the gap between perception and evidence, we need to start at the beginning of the roasting process.

We start here because it is essentially the method of “cooking” the coffee beans, and like everything else, the technique for cooking exists on a spectrum. The longer something is cooked, the more “done” it is. That level of “done-ness” then impacts the properties of the beverage. On the most basic level, this foundation serves as the basis for comparing different roasts.

The colorism of coffee is not an exact science, but there is a high-level trend with respect to its preparation. Darker beans are roasted at a higher temperature, and for longer, than lighter ones.

While it may seem like a trivial aspect of coffee making, the degree to which coffee beans are roasted ultimately determines the taste of the coffee in your cup. This is because the flavors we associate with coffee are only brought out through roasting. Raw coffee beans are soft and have little to no taste. Through roasting, they are completely transformed and display their aromatic, crunchy, and flavorful properties.

However, things do not always end up this way. As coffee is roasted to higher temperatures, the beans excrete oils on their surface that induce a bitter taste. If you’ve ever tasted a cup of “good” coffee and found it to be too bitter, this is likely why.

Conversely, lighter roasts bring out more of the nuanced flavors and aromas of the coffee beans. They tend to be brighter and more acidic than dark roasts. In fact, the preference from many coffee producing countries is for a light or medium blend. In Guatemala and Colombia, the darkest roasts are considered to be and an entirely separate beverage (like essentially coffee water). Since the flavors that these areas recognize as coffee are lost by roasting at high heat, it’s no wonder they classify coffee in this manner. And those close to coffee production struggle to understand our fascination with dark roasts in the United States. Thinking about it from their perspective, after all the labor and effort to cultivate the coffee bean, they must wonder why we take an ingredient with incredible flavor and burn it. It’s certainly a compelling question.

But understanding this preference for light and medium roasts also shows why coffee is such an incredibly unique drink. It has an incredibly varied geographical diversity in origin. Location, elevation, soil, and precipitation all impact the flavor profile of the beans.

However, in ordering the darkest roast, you risk losing its distinctive flavor profile by bringing out the bitterness of the bean. For what it’s worth, high heat roasting also reduces your margin of error. Like every other cooking technique, there is variance in execution and not all baristas are created equal. By cooking for too long at a high temperature, there’s a chance the preparation may result in over-roasting or even burning your coffee. Comparing this to a lighter roast, that margin for error increases where it is less likely to burn the beans at lower temperatures.

Now after all that, we are still allowed to differ on our preference preparation. Some may prefer the smoothness of a nice dark roast, but we prefer the nuances of the lighter roasts. But not everyone drinks coffee for this reason, and not everyone cares about these properties. Instead, we’d wager that most coffee drinkers do so for one reason: caffeine. And this is where things may get a little awkward (and really nerdy).

Lighter roasts definitely have more caffeine.

To eliminate the variable of personal preference in taste, we did some research to find an objective study on caffeine concentration in coffee. One of the most thorough was published Food Chemistry Journal in 2000. Researchers conducted a variety of experiments related to coffee and its preparation to arrive at the above conclusion.

Looking at their findings, the high level trend is that the concentration of caffeine decreases with respect to cooking time. It is interesting to note that the actual coffee sample impacts the caffeine concentration. As we mentioned before, coffee can have incredible diverse origins. With no two varieties being alike, it should be no surprise that some are more robust to heat than others.

While the experiment modeled caffeine concentration with respect to roasting time, it did so assuming a constant temperature. For lighter roasts to have more caffeine, there needs to be a correlation between roasting temperature and caffeine concentration as well. To test this hypothesis , the researchers ran the same experiment with different temperatures and a constant cooking time.

Again, there is variance between coffee varieties, but the high level trend holds true. Caffeine concentration decreases as cooking temperature increases.

But the difference is not only due to the calculated caffeine concentration. Since roasting changes the physical properties of the beans, it is important to check the units of measurement (our engineering professors would be so proud of us - Who ever though we’d be using our education to teach strangers about coffee over the internet).

In general, lighter roasts have a shorter cooking time. This causes the cooked beans have a higher density compared to those prepared with a darker roast. This matters because the volume of coffee beans remains fairly constant after roasting (seriously they would be so proud). For this to be true, lighter roasts should have a higher mass compared to darker roasts.

This phenomenon is observed through the mass percentage of each bean that is lost with respect to roasting temperature and time. At both higher cooking temperatures and longer cooking time, there is an difference in final mass that increases with both conditions.

As a result, we would expect an individual particle of ground light roast to contain more caffeine than a particle of ground dark roast because it has a higher mass.

So by now you might be thinking, “You’re boring us. What does this mean for your final cup of coffee?”

When equal volumes of coffee are measured (i.e. number of scoops), light roast will have more caffeine because it has a higher mass occupying the same volume.

There you have it. Caffeine addicts, begin to ask your barista if they understand the difference between volume and weight. Adjust your orders as needed and thank us later.