Taste perception of bitter compounds in young and elderly persons: Relation to lipophilicity of bitter compounds

Covariation in individuals’ sensitivities to bitter compounds: Evidence supporting multiple receptor/transduction mechanisms

“…The finding that subjects who are insensitive to PROP give lower ratings to bitter compounds than do subjects more sensitive to PROP has been found by other researchers as well (e.g., Lawless, 1979;Schiffman et al, 1994). Although these results initially may seem to contradict the lack of PROP correlations with other compounds reported above, the apparent discrepancy is due to the fact that only a very few subjects were shown to rate all compounds consistently lower than other subjects.…”

“…Similarly, studies have failed to find a clear relationship between urea and PROP/PTC (Hall et al, 1975;Mela, 1989;Yokomukai et al, 1993), at either threshold levels (Hall et al, 1975;Schiffman et al, 1994) or suprathreshold concentrations (Mela, 1989;Yokomukai et al, 1993). Following this trend, Mela (1989) failed to find a significant difference between PROP tasters and nontasters in the suprathreshold concentrations of SOA and denatonium benzoate, and both Schiffman et al (1994) and Boughter and Whitney (1993) failed to find a significant difference between PROP taster groups in the thresholds of SOA.…”

“…For example, the number of methyl groups will likely be positively correlated with compound lipophilicity (cf. Schiffman et al, 1994). Thus, this cluster may involve a mechanism dependent on lipophilic stimuli.…”

“…Although some studies have found a significant positive relationship between PROP or PTC sensitivity and quinine sensitivity (Gent & Bartoshuk, 1983;Jefferson & Erdman, 1970;Lawless, 1979;Leach & Noble, 1986), several other studies have failed to find such a relationship either for suprathreshold ratings of quinine (Bartoshuk, 1979;Bartoshuk, Rifkin, Marks, & Hooper, 1988;Frank & Korchmar, 1985;Mela, 1989;Schifferstein & Frijters, 1991;Yokomukai et al, 1993) or for quinine thresholds (Fischer & Griffin, 1963;Hall et al, 1975;Lawless, 1979;Schiffman et al, 1994).…”

“…Hall et al (1975) found that "sensitivity to the taste of PTC predicts sensitivity to caffeine," using both threshold measurements and magnitude estimations of suprathreshold concentrations of caffeine, but other studies failed to find a significant difference between tasters and nontasters in the ratings of suprathreshold concentrations of caffeine (Leach & Noble, 1986;Mela, 1989) or in caffeine thresholds (Schiffman et al, 1994).…”