No abstract

The importance of stimulus timing and location on the perceptual integration of taste and odour was studied based on a sub-threshold methodology. From a panel of 16 people, 12 showed the integration effect previously reported while 4 showed no effect. The experiment was repeated using retronasal and orthonasal delivery of the odour and with tastant present or absent in the mouth. Integration of taste and odour only occurred when both stimuli were present at the same time. Retro- or orthonasal presentation both produced integration providing that tastant delivery was synchronous but the threshold values for the two presentation methods were different. The relevance of these findings to flavour perception under realistic conditions is considered.

Cross-modal interactions between aroma, sweetness, and acidity were studied. A series of samples was presented to trained panelists who assessed strawberry flavor intensity using magnitude estimation with a reference modulus. The delivery of aroma stimuli from the different solutions was measured by monitoring exhaled breath using atmospheric pressure chemical ionization-mass spectrometry to determine whether there were any physicochemical effects on volatile release; no significant differences were noted. Three-dimensional predictive models were built to describe perceived strawberry flavor intensity as a function of concentrations of sucrose, acid, and volatiles. Analysis of the data identified two groups of panelists with different responses: For Group 1, increasing sucrose and/or acid levels also increased the perceived flavor intensity. For Group 2, changing sucrose concentrations had little effect, but increasing acid and/or volatile levels did. The results show different effects of organic and inorganic acids on perception, as well as clear interactions between the modalities of taste (sugar and acid) and aroma. The clustering of panelists' responses suggests that this phenomenon may depend on prior associations between the fruity flavor and the tastants.

Perception of flavor is a complex process involving the integration of taste and aroma. Few functional magnetic resonance imaging (fMRI) studies have assessed the crossmodal interactions which result in flavor perception, and all previous studies have used a retro-nasal aroma delivery with a delayed swallow, which delays retro-nasal aroma release, and thus, alters taste and aroma integration. In this paper, we assess crossmodal interactions in flavor processing using an immediate swallow fMRI paradigm in 13 healthy volunteers. We compare unimodal taste (sucrose) and unimodal retro-nasal aroma stimuli, with a congruent taste and aroma combination (flavor), to assess crossmodal flavor interactions using an immediate swallow paradigm. Subtraction and conjunction analysis methods are described, and the use of a control stimulus is addressed. Subtraction analysis was found to reveal areas of anterior insula, frontal operculum, anterior cingulate, and orbitofrontal cortex, whilst the conjunction analysis revealed additional active areas in oral somatosensory areas (SI), rolandic operculum and posterior cingulate, supporting the hypothesis that taste, olfactory, and tactile sensations are integrated to produce a flavor percept.