Impact of Interactions between Melanoidins and Caffeine on the Bitter Taste of Coffee Beverages

Abstract Since the discovery of caffeine in 1819 by Runge, its role in the sensory perception of coffee remains unclear. To further investigate its influence, the caffeine–chlorogenate complex was examined using NMR spectroscopy as well as sensory experiments. It was found that the complex formation between caffeine and chlorogenic acid (CQA) has no impact on the bitter taste of caffeine. The changes of the 1H NMR resonance signals of caffeine in the coffee matrix compared to an aqueous reference solution suggested that caffeine interacts, besides its complex with CQA, with the high molecular weight melanoidins containing fraction of coffee. After isolating the melanoidins from the coffee beverage, these interactions were confirmed in model studies using 1H NMR spectroscopy. Sensory studies with caffeine and the melanoidins in their natural concentrations showed a strong reduction in bitter intensity by about half compared to an aqueous caffeine solution of the same concentration.