title: A psychophysical investigation of binary bitter-compound interactions.
abstract: 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), quinine-HCl (QHCl), sucrose octaacetate (SOA), urea, L-tryptophan (L-trp), L-phenylalanine (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, and ranitidine; 2, SOA and 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.
authors.affiliation: Monell Chemical Senses Center, 3500 Market St, Philadelphia, PA 19104, USA. keast@monell.org
authors.forename: Russell S J
authors.initials: RS
authors.lastname: Keast
authors.forename: Melanie M E
authors.initials: MM
authors.lastname: Bournazel
authors.forename: Paul A S
authors.initials: PA
authors.lastname: Breslin
mesh_terms: D000328:Adult; D016000:Cluster Analysis; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004357:Drug Synergism; D005260:Female; D006801:Humans; D007206:Individuality; D008297:Male; D008875:Middle Aged; D010649:Phenylalanine; D011601:Psychophysics / Q000379:methods; D000644:Quaternary Ammonium Compounds; D011899:Ranitidine; D013268:Stimulation, Chemical; D013650:Taste Buds / Q000187:drug effects / Q000502:physiology*; D013652:Taste Threshold / Q000502:physiology*; D014364:Tryptophan; D014508:Urea
chemical_list: D004338:Drug Combinations; D010649:Phenylalanine; D000644:Quaternary Ammonium Compounds; D011899:Ranitidine; D014364:Tryptophan; D014508:Urea; C043414:denatonium