Are the tastes of polycose and monosodium glutamate unique?

To study whether Polycose and monosodium L-glutamate (L-MSG) have unique tastes differing from the traditional four basic tastes, chemosensory profiles were established for Polycose, L-MSG and a group of related compounds (sucrose, maltose, monosodium D-glutamate (D-MSG), sodium chloride, calcium chloride). Flavors were assessed using whole-mouth tests in human subjects with nose open or clamped to reduce olfactory input. Polycose (a mixture of glucose-based oligosaccharides) had a flavor consisting of an olfactory component and a maltose-like taste. L-MSG and D-MSG profiles differed from each other, and from NaCl and CaCl2. L-MSG had a lower threshold and a higher frequency of 'other' tastes than the D form. The data do not support a 'polysaccharide' taste, but suggest a chiral receptor site for 'umami' taste.