Physiological Studies on Umami Taste

Abstract

The first electrophysiological studies on umami taste were conducted with rats and cats. Unlike humans, these animals did not show a large synergism between monosodium glutamate (MSG) and disodium guanylate (GMP) or disodium inosinate (IMP). The taste nerve responses of these animals to umami substances were not differentiated from the salt responses. The canine taste system was sensitive to umami substances and showed a large synergism between MSG and GMP or IMP. The umami substances showed no enhancing effects on other basic tastes. Amiloride, an inhibitor for the response to NaCl, did not inhibit the large response induced by the synergism between MSG and the nucleotides, indicating that the response to the umami substances is independent of the response to salt. Single-fiber analysis on the responses of mouse glossopharyngeal nerve and monkey primary taste cortex neurons also showed that the responses to umami substances are independent of other basic tastes. On the basis of these results, it was proposed that the umami taste is a fifth basic taste, and that there is a unique receptor for umami substances. Hence, we compared the taste of agonists for brain glutamate receptors. In humans, the order of intensity of umami taste induced by a mixture of 0.5 mmol/L GMP and 1.5 mmol/L of various agonists was glutamate > ibotenate > L(+)-2-amino-4-phosphonobutyric acid (L-AP4) = (+/-)1-aminocyclopentane-trans-1,3-dicarboxylic acid (ACPD). Kainate, N-methyl-D-aspartic acid (NMDA) and (RS)-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), which are agonists for ionotropic receptors, had no umami taste. It was concluded that the umami receptor is not identical to any known glutamate receptors; there seems, therefore, to be a unique receptor for umami.

Consensus meeting: monosodium glutamate – an update

“…In electrophysiological studies, recording from afferent chorda tympani fibers in dogs, taste cells were found that responded to GLU application to the tongue independent of sodium receptor stimulation (sodium receptors were blocked with amiloride) (Nakamura and Kurihara, 1991). In addition to these earlier results, glossopharyngeal afferent fibers were identified in mice that responded to GLU (and mononucleotide) applications to the tongue, but not to the other basic tastants (Kurihara and Kashiwayanagi, 2000).…”

“…The result was that the umami taste receptor is probably a metabotropic, but not an ionotropic GLU receptor, perhaps somewhat similar to, but not identical with the metabotropic GLU receptor subtype-4. Kurihara and Kashiwayanagi (2000) concluded from their human studies that the umami taste receptor may be a unique GLU receptor subtype.…”

Influence of Supercritical CO₂ Extraction of Schisandra Chinensis on Antioxidant Status, Carcass and Meat Quality of AA Broilers

“…It is known that IMP contributes to the pleasant, fresh flavor of the meat (Howgate, 2005). Furthermore, IMP acts as a flavor enhancer of meaty foods, especially L-glutamate, an umami flavor (Kurihara and Kashiwayanagi, 2000;Kawai et al, 2002;Li et al, 2002), IMP is as an important indicator to measure the meat flavor. Some studies showed that IMP heated in water and fat could produce obvious meat flavor (Heath and Reineccius, 1986).…”

Seasonal changes in the biochemical composition ofEvechinus chloroticusgonads (Echinodermata: Echinoidea)

“…The omission of glutamate from synthetic extracts generally resulted not only in the expected decrease in umami taste but, in the case of the sea urchin extract, led to an increase in sweetness (Fuke & Ueda 1996). Glutamate flavour has also been shown to intensify in the presence of a very small concentration of nucleotides such as inosine 5?-monophosphate (IMP) or guanosine monophosphate (GMP) (Kurihara & Kashiwayanagi 2000;Kawai et al 2002); however, IMP or GMP concentrations were not quantified in the current study.…”