The addition of CO2 to traditional taste solutions alters taste quality

Previous studies of the effect of carbonation on taste perception havesuggested that it may be negligible, manifesting primarily in increases inthe perceived intensity of weak salt and sour stimuli. Assuming CO2solutions in the mouth stimulate only trigeminal nerve endings, this resultis not altogether surprising; however, there are neurophysiological dataindicating that CO2 stimulates gustatory as well as trigeminal fibers. Inthat case, carbonation might alter the quality profile of a stimuluswithout producing substantial changes in overall taste intensity--much asoccurs when qualitatively different taste stimuli are mixed. To addressthis possibility, subjects were asked to rate the total taste intensity ofmoderate concentrations of stimuli representing each of the basic tastesand their binary combinations, with an without added carbonation. They thensubdivided total taste intensity into the proportions of sweetness,saltiness, sourness, bitterness and 'other taste qualities' they perceived.The addition of carbonation produced only small increases in ratings oftotal taste intensity. However, rather dramatic alterations in the qualityprofiles of stimuli were observed, particularly for sweet and salty tastes.The nature of the interaction is consistent with a direct effect ofcarbonation/CO2 on the gustatory system, although the possibility that atleast some of the observed effects reflect trigeminal-gustatoryinteractions cannot be ruled out.