Retronasal odor enhancement by salty and umami tastes

It has been shown that congruent food odors are enhanced by sweet taste, but not by sour or bitter taste. This raises questions regarding the underlying conditions of retronasal odor enhancement by taste. We speculate that a taste quality that signals the presence of nutritive or beneficial substances (e.g., sweet carbohydrate), as opposed to potentially harmful substances (e.g., toxins, spoilage), can enhance a congruent odor. This study aimed to investigate this possibility by testing two other taste qualities, saltiness and umami, which signal the presence of minerals and protein. The study also examined the possible occurrence of saltiness and umami enhancement by odors and factors that may affect both taste and odor enhancement. Over five sessions, subjects rated (1) intensities of saltiness, bitterness, umami, and specific odor of tastants (NaCl, MSG, MPG, caffeine), odorants (chicken, soy sauce odor), and all possible binary mixtures, (2) degree of liking/disliking of the odorants in the absence and presence of the tastants, (3) degree of congruency of odorants alone and with tastants, and (4) degree of perceptual similarity between tastants and odorants. Results showed that saltiness and umami enhanced chicken and soy sauce odor intensities, but the odors did not enhance saltiness and umami intensities. Importantly, the degree of odor enhancement was highly correlated with the degree of taste-odor congruency, but less so with the degree of perceptual similarity between taste and odor. These findings confirm our hypotheses that the quality of taste dictates the ability to enhance food odors and that the degree of taste-odor congruency can modulate the degree of odor enhancement. (C) 2015 Elsevier Ltd. All rights reserved.