Does Darker Coffee Roast Really Mean More Caffeine?

Caffeine is the primary reason most people consume coffee! Especially for professionals who need to work late nights, caffeine is an absolute treasure. They quickly down several cups of coffee, just to seek the mental alertness that caffeine provides throughout the night!

Does Roasting Really Affect Caffeine Content?

Recently, FrontStreet Coffee briefly discussed the difference in caffeine content between decaffeinated and regular coffee, which prompted some readers to ask in the comments: I've heard that coffee brewed from dark-roasted beans contains more caffeine than coffee brewed from light-roasted beans? Does the degree of roasting really affect caffeine content?

For a long time, the question of whether roasting degree affects caffeine content has generally been divided into two camps online. One camp believes that dark-roasted beans contain more caffeine than light-roasted beans! Their viewpoint stems from understanding coffee bean density: the deeper the roast, the lighter the bean's mass. If you use equal weight of coffee beans to brew coffee, dark-roasted beans require more quantity than light-roasted beans. Additionally, dark-roasted beans have a more porous structure, making it easier to extract substances from within the beans. Therefore, this group believes that at equal weight, coffee brewed from dark-roasted beans contains more caffeine than coffee brewed from light-roasted beans!

The other camp believes that dark-roasted beans contain less caffeine than light-roasted beans, mainly because: caffeine's melting point is between 235°C-238°C. Although typical roasting rarely reaches this temperature, caffeine sublimates at 178°C! Therefore, they believe that dark-roasted coffee beans contain less caffeine!

To provide a definitive answer to both camps, the Association for Science and Information on Coffee conducted an experiment using one variety of Arabica coffee beans with three "cooking methods": one light roast, one medium roast, and one dark roast! After roasting, measurements were taken, yielding the following results: 1.37% (light), 1.31% (medium), 1.31% (dark). Although light-roasted coffee beans contained only 0.06% more caffeine than dark-roasted coffee beans, this finding does confirm that dark-roasted coffee contains slightly less caffeine than light-roasted coffee.

The Weight Loss Factor

However, we haven't yet accounted for weight loss! Light-roasted coffee has a weight loss of 11-13%, while dark-roasted coffee has a weight loss of 15-17%. Therefore, although dark-roasted coffee loses trace amounts of caffeine during the roasting process, these losses are nearly negligible when calculated proportionally!

If equal gram amounts of beans are used to extract coffee with equal parameters, and the caffeine content in the coffee liquid is calculated, dark-roasted coffee will have higher extraction efficiency due to its porous characteristics, resulting in caffeine content in the final coffee liquid that is indeed higher than light-roasted coffee. Both viewpoints are correct, but each is somewhat one-sided.

The True Key Factor Affecting Caffeine Content

Those who regularly follow FrontStreet Coffee can probably guess the main factor affecting caffeine content! That's right - it's the "bean variety." The genetics of coffee bean varieties determines the baseline caffeine content. For example, as we often mention: Arabica varieties contain caffeine in the range of 0.9-1.4%, while Robusta varieties contain twice as much caffeine as Arabica, in the range of 1.8-4%! The caffeine content then changes based on growing conditions and post-harvest processing!

However, not all caffeine within coffee beans is extracted during brewing. Coffee beans contain approximately 30% extractable substances, including caffeine, and their release is critically linked to extraction efficiency!

For example: 15g of Arabica coffee beans extracted through pour-over using a 1:15 coffee-to-water ratio will yield approximately 200ml of coffee liquid. Assuming this properly extracted pour-over coffee contains about 100-150mg of caffeine, we can increase its extraction efficiency by adjusting to a finer grind, raising water temperature, or extending extraction time. Ultimately, the caffeine content in this equal amount of coffee liquid will increase accordingly. Conversely, if we reduce extraction efficiency, the caffeine content will decrease accordingly!

Conclusion

Therefore, we now understand that the roasting degree of beans has virtually no effect on caffeine! What can affect the caffeine content in beans are genetics, growing conditions, and post-harvest processing; what affects caffeine content in coffee liquid is extraction efficiency during brewing, not the degree of roasting!

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