Activity-guided fractionation of an aqueous extract of overfermented cocoa beans, which were recently found to be a rich source of previously unknown taste enhancing substances, revealed the presence of a series of taste modulating short peptides. Fractionation was achieved by means of sequential solvent extraction, medium pressure liquid chromatography, as well as preparative high pressure liquid chromatography, and the taste modulating activity was determined by means of matrix assisted taste dilution analysis. By means of ultra performance liquid chromatography-time-of-flight-mass spectrometry (UPLC-ToF-MS) screening, liquid chromatography-MS/MS methods, and customized syntheses, numerous short peptides could be identified in the taste modulating fractions. Sensory experiments of the target peptides showed umami enhancing and salt taste enhancing properties as well as kokumi effects when applied in a savory taste matrix. Evaluation of the taste threshold concentrations in model broth demonstrated a high taste modulating potential of 11 out of 13 identified peptides. Lowest threshold concentrations were determined for the salt taste enhancing tripeptide pEEE (55 μmol/L) and the kokumi active tripeptide VPA (90 μmol/L). Furthermore, a large number of dipeptides, carrying either a prolyl- or pyro-glutamyl moiety were located in the aqueous extract, exhibiting taste modulating properties and revealing a pH dependency of the taste modulating effect of the savory taste matrix. Additionally, synergistic effects of a mixture of five umami enhancing pyro-glutamyl dipeptides in the model matrix were demonstrated.
Keywords: overfermented cocoa; peptides; taste dilution analysis; taste enhancer; taste modulation.