A study published June 3, 2026 in the American Chemical Society's Journal of Agricultural and Food Chemistry explains why coffee doesn't carry the sharp bitterness of pure caffeine. Researchers Michael Gigl, Johanna Kreissl, and Oliver Frank, from the Leibniz Institute for Food Systems Biology at the Technical University of Munich, used a trained sensory panel to compare how caffeine bitterness is perceived in water versus in coffee.
The finding: melanoidins — brown molecules formed during roasting through the Maillard reaction — together with chlorogenic acid, cut perceived caffeine bitterness by roughly half. The proposed mechanism is that high-molecular-weight melanoidins bind to caffeine, reducing the amount of free caffeine available to activate bitter taste receptors.
Researchers have yet to determine whether lighter roasts, which produce fewer melanoidins, let more caffeine bitterness come through compared with darker roasts — a question left open for future study.
Source: Daily Coffee News