Detection of Inosine Monophosphate and the Umami Synergistic Effect Using a Taste Sensor with a Surface-Modified Membrane

A taste sensor composed of a lipid/polymer membrane using tetradodecylammonium bromide (TDAB) as the lipid and modified with 2,6-dihydroxyterephthalic acid (2,6-DHTPA) has recently been reported to exhibit high sensitivity and selectivity toward the umami substance monosodium L-glutamate (MSG). In this study, we aimed to investigate whether this sensor can also detect another umami substance, inosine monophosphate (IMP), and whether it can evaluate the umami synergistic effect-an enhancement of umami intensity-observed when IMP is mixed with MSG. Furthermore, ¹H-NMR analysis was conducted to examine the nature of interactions between the membrane modifier and umami substances. The results demonstrated that IMP can be successfully detected using the sensor, and that, as previously reported for MSG, sensor sensitivity is influenced by the presence or absence of intramolecular hydrogen bonding within the modifier and intermolecular hydrogen bonding between the modifier and the umami substance. In addition, the response to mixed solutions of MSG and IMP was greater than the sum of individual responses, indicating that the umami synergistic effect can be evaluated using the taste sensor. NMR measurements also revealed that the presence of the membrane modifier enhances the interaction between IMP and MSG, supporting the observed synergistic effect.