Binary Bitter-Compound Taste Interactions

The aim of this study was to determine if taste interactions occur when bitter stimuli are mixed. Eight bitter stimuli were employed: Denatonium benzoate (DB), (L-phe), Ranitidine-HCl, and Tetralone®. The first experiment constructed individual psychophysical curves for each subject (n=19) for each compound to account for individual differences in sensitivities when presenting bitter compounds in Experiment 2. Correlation analysis revealed two groupings of bitter compounds at low intensity, (1/ L-trp, L-phe, & Ranitidine, 2/ SOA & QHCl), but the correlations within each group decreased as the perceived intensity increased. In Experiment 2, intensity ratings and two-alternative forced-choice discrimination tasks showed that bitter compounds generally combine additively in mixture and do not show interactions with a few specific exceptions. The methods employed detected synergy among sweeteners, but could not detect synergy among these eight bitter compounds. In general, the perceived bitterness of these binary bitter-compound mixtures was an additive function of the total bitter inducing stimuli in the mouth.