Why doesn’t coffee taste like caffeine?

Though decaf fans might disagree, caffeine is a critical component of a cup of joe. This compound is incredibly bitter on its own, but regular coffee itself is not. A team reporting in ACS’ Journal of Agricultural and Food Chemistry is investigating why and explains that the answer may lie within interactions between caffeine and other coffee molecules called melanoidins that are produced during the roasting process.  

Previously, taste-testers have described caffeine as highly bitter, even medicinal-tasting. And yet, a cup of coffee usually has a pleasant mouthfeel. Because that extreme bitter taste is gone, Oliver Frank, Johanna Kreissl, and Michael Gigl wanted to figure out why. “The significance of this work lies in explaining why coffee beverages do not taste of caffeine, even though the caffeine concentration of coffee is far above the perceivable level,” explains Gigl. 

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, coffee masked caffeine’s distinctive taste until researchers added 10 times the normal amount of caffeine present in a typical brew. 

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 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. 

The authors do not have an external funding source for this work. 

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