Molecular Definition of Black Tea Taste by Means of Quantitative Studies, Taste Reconstitution, and Omission Experiments

Recently, bioresponse-guided fractionation of black tea infusions indicated that neither the high molecular weight thearubigens nor the theaflavins, but a series of 14 flavon-3-ol glycopyranosides besides some catechins, might be important contributors to black tea taste. To further bridge the gap between pure structural chemistry and human taste perception, in the present investigation 51 putative taste compounds have been quantified in a black tea infusion, and their dose-over-threshold (Dot) factors have been calculated on the basis of a dose/threshold relationship. To confirm these quantitative results, an aqueous taste model was prepared by blending aqueous solutions of 15 amino acids, 14 flavonol-glycosides, 8 flavan-3-ols, 5 theaflavins, 5 organic acids, 3 sugars, and caffeine in their "natural" concentrations. Sensory analyses revealed that the taste profile of this artificial cocktail did not differ significantly from the taste profile of the authentic tea infusion. To further narrow the number of key taste compounds, finally, taste omission experiments have been performed, on the basis of which a reduced recombinate was prepared containing the bitter-tasting caffeine, nine velvety astringent flavonol-3-glycosides, and the puckering astringent catechin as well as the astringent and bitter epigallocatechin-3-gallate. The taste profile of this reduced recombinate differed not significantly from that of the complete taste recombinate, thus confirming these 12 compounds as the key taste compounds of the tea infusion. Additional sensory studies demonstrated for the first time that the flavanol-3-glycosides not only impart a velvety astringent taste sensation to the oral cavity but also contribute to the bitter taste of tea infusions by amplifying the bitterness of caffeine.