Why doesn’t coffee taste like caffeine?

Caffeine itself is considered highly bitter and is often described as having a medicinal taste. Nevertheless, coffee is known for its balanced and rounded flavor profile. This apparent paradox was investigated by Michael Gigl at the ZIEL – Institute for Food and Health, and Oliver Frank from the Chair of Food Chemistry and Molecular Sensory at TUM in Freising, together with Johanna Kreissl from the Leibniz-LSB@TUM. In a study published in the Journal of Agricultural and Food Chemistry, they explain that the answer may lie in interactions between caffeine and other coffee molecules called melanoidins, which are formed during roasting.

Through a series of tests aided by a trained panel, the researchers discovered that caffeine must be interacting with other molecules present in coffee that significantly reduce its bitterness.  In fact, the coffee masked the characteristic taste of caffeine until the researchers added many times the natural amount of caffeine present in a typical cup of coffee.

To find the coffee molecules responsible for this effect, the team ran taste-tests of caffeine in solution combined with additional compounds: chlorogenic acid, which is naturally present in coffee beans, and/or melanoidins, which are high-molecuar-weight products of the Maillard reaction that occurs during roasting. The tasting panel found that when both compounds were combined with caffeine, the bitter taste was reduced by about half. Frank suspects that caffeine and melanoidins form a complex that, due to its size, prevents interaction with the bitter taste receptors on our tongues. And the strength of the bond between caffeine and melanoidins may differ between different roasting processes, though future work is needed on this point. 

“A plethora of bitter stimuli, generated during the roasting process, culminate in the unique, bitter taste of coffee beverages,” concludes Gigl. This knowledge can inform further research into these unique interactions and may even contribute to better coffee products, such as flavorings or instant coffees.

Original publication: Michael Gigl, Johanna Kreissl, and Oliver Frank: Impact of Interactions between Melanoidins and Caffeine on the Bitter Taste of Coffee Beverages. Journal of Agricultural and Food Chemistry (03.06.2026) https://doi.org/10.1021/acs.jafc.5c17022

This TUM article is based on a press release from Sarah Michaud of the American Chemical Society