I have heard -and read- dozens of times that dark roast coffee has more caffeine than light roasts.
Researchers Niny Z. Rao and Megan Fuller challenged this myth through their groundbreaking study in 2017 already . Moreover, their work suggests that brewing methods, time of extraction, and grind size are as important -or more- than roasts.
Of course, you might already know that when it comes to coffee-as all good things- nothing can beat nature. Robusta, a plant variety, has roughly twice the caffeine content than Arabica, the most valued and harvested one .
But now, let’s get to it!
What Does Roasting Mean Anyway?
Putting it simply, roasting is cooking green coffee beans. Raw beans suffer a dramatic transformation through the fire. This isn’t surprising, but the complexity of this process goes a lot further than cooking. Craft and science joined efforts at the start of the XXI century , and we have still many questions to answer.
Coffee roasting has changed and evolved for centuries, heavily influenced by local preferences and (shady) business practices. In origin, many families still roast coffee beans with pans.
In the heat of burning firewood, pan-roasting is a highly skilled process that demands excellent sensory skills (hearing, seeing, and smelling are essential). In the other extreme, advanced technology informs roasters in large factories and micro-roasteries all over the world.
Variance in roasting preferences is wide and wild. From the hardcore light roasts served in the Nordic countries to the oily, dark, almost burnt French and Italian dark roasts.
Taste preferences have influenced deeply over roasting practices, and new global coffee culture has emerged, challenging these local habits. In doing so, many coffee lovers have developed a love-hate relationship with specialty coffee.
Some of the most controversial aspects of high-end coffee are taste and aroma. Specialty beans offer dozens of unexpected aromatic notes, while both scientists and experts are still looking for ways to unveil the craft behind them.
In the late XX century and at the beginning of the XXI century, coffee science jumped into the craft-dominated roasting world.
Furthermore, as public interest in caffeine consumption grew, researchers have been studying other variables such as brewing method, grind size, water temperature, plant varieties, and brewing times.
How Much Caffeine is in Dark Roast Coffee Compared to Other Roasts
According to different studies, dark roasted coffee has less caffeine than medium roast coffee.
We used to think that dark roasted coffee is stronger than a lightly roasted one. Arguably, we might be linking bitterness in dark roasts with a stronger shot of caffeine. However, scientific evidence points in another direction (not the opposite, to be precise.)
In 2017, Nature published a study by Niny Rao and Megan Fuller where they found that medium roasts have higher caffeine concentrations under different conditions.
Moreover, using similar grind sizes, hot, and cold-brew methods, medium roasted coffee always had more caffeine in it.
Curiously enough, antioxidants and caffeine content are higher in medium roasts than in light roasts and green coffee beans too.
All in all, the results are clear enough, albeit complex. Like taste, the development of coffee roasts properties isn’t linear and there is still a lot to learn from roasting science.
How does the brewing method matter?
We know that espresso has more antioxidants than any other drink, including other coffee beverages. However, several studies suggest that drip coffee and cold-brew can have more caffeine than espresso.
This is particularly true considering the average size of a drip coffee serving in comparison with a cup of espresso. Before Starbucks, the coffee mug standard size was about 8 to 10 ounces. However, in the US, coffee mugs have been traditionally larger than in most places and can hold up to 25 ounces.
If we consider caffeine intake, instead of content, it would be obvious that a 25 ounces mug of drip coffee would result in drinking a lot more caffeine than a cup of espresso. However, as espresso is a lot more concentrated than drip coffee, it tends to have more caffeine per ounce .
What’s the actual difference between coffee roasts?
Roasts look, smell, taste, and feel different to touch. Additionally, their chemical and physical properties change. Light roasts are heavier than dark roasts, and during roasting development, the caffeine and antioxidants contents change significantly.
Moreover, roasting levels aren’t the only important variable when ‘cooking’ green coffee. Roasting profiles play a huge deal in chemical changes too . In other words, the speed of roasting alters the result as well, just like cooking with low fire for hours produces a different result in cooking than a quick preparation over a high fire.
During the last few decades, roasters have found that little tweaks can help to develop different aromatic profiles, offering very exciting tastes and scents.
In terms of quality, dark roasts have fallen into disgrace, as we link them with more traditional and shady practices in the industry. However, dark roasted coffee can offer a delicious taste and mouthfeel. In my opinion, bad dark roasts are as bad as any other low-quality coffee.
Roasting profiles alone aren’t enough to decide if one coffee is better than another. Coffee varieties, terroir, cherries selection, processing, storage, grind size, and brewing method play a significant role in the quality of the resulting cup.
What does this mean?
Medium roasts have the highest caffeine -and antioxidants- content, in comparison with light and dark roasts. Playing with grind size and brewing methods can change how much caffeine is in our cup of coffee.
In conclusion, roasting levels are the second most important factor after coffee varieties in terms of caffeine content.
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For more interesting facts and articles about coffee science, you can read the following:
- Great Coffee 101: Best Coffee Hacks
- Antioxidants in Coffee: Worth the Buzz?
- Water Temperature: Does It Matter For Drip And Pour-Over Coffee Brewing?
- Fuller, M., Rao, N.Z. The Effect of Time, Roasting Temperature, and Grind Size on Caffeine and Chlorogenic Acid Concentrations in Cold Brew Coffee. Sci Rep 7, 17979 (2017). https://doi.org/10.1038/s41598-017-18247-4
- Olechno, E.; PuscionJakubik, A.; Zujko, M.E.; Socha, K. Influence of Various Factors on Caffeine Content in Coffee Brews. Foods 2021, 10, 1208. https://doi.org/10.3390/foods10061208
- Yeretzian, C., Jordan, A., Badoud, R. et al. From the green bean to the cup of coffee: investigating coffee roasting by on-line monitoring of volatiles. Eur Food Res Technol 214, 92–104 (2002). https://doi.org/10.1007/s00217-001-0424-7