THE ADDITION OF CO2 TO TRADITIONAL TASTE SOLUTIONS ALTERS TASTE QUALITY

Previous studies of the effect of carbonation on taste perception have suggested that it may be negligible, manifesting primarily in increas es in the perceived intensity of weak salt and sour stimuli. Assuming CO2 solutions in the mouth stimulate only trigeminal nerve endings, th is result is not altogether surprising; however, there are neurophysio logical data indicating that CO2 stimulates gustatory as well as trige minal fibers. in that case, carbonation might alter the quality profil e of a stimulus without producing substantial changes in overall taste intensity-much as occurs when qualitatively different taste stimuli a re mixed. To address this possibility, subjects were asked to rate the total taste intensity of moderate concentrations of stimuli represent ing each of the basic tastes and their binary combinations, with and w ithout added carbonation. They then subdivided total taste intensity i nto the proportions of sweetness, saltiness, sourness, bitterness and 'other taste qualities' they perceived. The addition of carbonation pr oduced only small increases in ratings of total taste intensity. Howev er, rather dramatic alterations in the quality profiles of stimuli wer e observed, particularly for sweet and salty tastes. The nature of the interaction is consistent with a direct effect of carbonation/CO2 on the gustatory system, although the possibility that at least some of t he observed effects reflect trigeminal-gustatory interactions cannot b e ruled out.