The structure of the human umami receptor and orthosteric and allosteric-binding modes of umami compounds have been proposed. The relationship between in vivo concentration of umami compounds (on the tongue) and the perception of umami flavor does not appear to have been investigated. Using a swabbing technique similar to Davidson and co-workers, taste perception and analytical chemistry were used to study the relationship between taste stimuli and taste perception. Synergistic effects of orthosteric and allosteric-binding umami compounds were also studied.