Effects of Stimulus Intensity on Odor Enhancement by Taste

Abstract

Enhancement of retronasal odors by sucrose has been shown to be a reliable perceptual phenomenon of taste–odor interactions. It is unknown, however, whether stimulus intensity modulates the degree of odor enhancement. The present study was therefore designed to investigate how the intensity of odor and taste alone affects the degree of odor enhancement. In the first experiment, subjects rated the intensities of taste and odor for aqueous solutions of sucrose and citral at three concentrations, both alone and in binary mixtures. The results showed that sucrose significantly increased the “citrus” ratings to an extent that was inversely related to the intensity of citral alone. Interestingly, the increase in sucrose intensity had insignificant effects on odor enhancement. To test the reliability of the relationship between odor intensity and the degree of enhancement, a second experiment was conducted in which subjects inhaled three concentrations of citral in vapor phase via the mouth while tasting sucrose. This procedure also provided an opportunity to rule out the possibility that the odor enhancement is the result of, at least in part, physicochemical interactions between sucrose and volatiles. Consistent with the previous results, the presence of sucrose in the mouth significantly enhanced the “citrus” ratings compared to when citral was inhaled alone, and the odor intensity relationship was preserved. These findings demonstrate that odor enhancement by sucrose is a perceptual phenomenon that occurs independent of physicochemical interactions between flavor components and that the degree of enhancement is greater when retronasal odors are weak.