Interactions between CO2 oral pungency and taste

Two experiments are reported in which the perceptual interactions between oral pungency, evoked by CO2, and the taste of each of four tastants--sucrose (sweet), quinine sulfate (bitter), sodium chloride (salty), and tartaric acid (sour)--were explored. In experiment 1 the effect of three concentrations of each tastant on the stimulus-response function for perceived oral pungency, in terms of both rate of change (slope) and relative position along the perceived pungency axis, was determined. In experiment 2 the effect of three concentrations of CO2 on the stimulus-response function for the perceived taste intensity of each tastant was examined. Results show that the characteristics of the mutual effects of tastant and pungent stimulus depend on the particular tastant employed. Sucrose sweetness and CO2 oral pungency have no mutual effect; sodium chloride saltiness or tartaric acid sourness and CO2 oral pungency show mutual enhancement; and quinine sulfate bitterness abates CO2 oral pungency, whereas CO2 has a double and opposite effect on quinine sulfate bitterness--at low concentrations of bitter tastant CO2 enhances bitterness, and at high concentrations of bitter tastant CO2 abates bitterness. It is suggested that the perceptual attributes of saltiness and sourness are closer, from a qualitative point of view, to oral pungency than are the attributes of bitterness and sweetness.