The sixth taste?

Five taste qualities are recognized in humans: sweet, bitter, sour, salty, and umami. Rats and some other species may also have a sixth taste. Behavioral and electrophysiological data suggest that rats can taste polysaccharides derived from starch. Furthermore, the tastes of sugars and polysaccharides appear to differ in quality. Rats also discriminate different types of polysaccharide and starch molecules. Recent studies indicate that sweet taste is mediated by a T1R2 and T1R3 receptor complex but the identity of the hypothesized polysaccharide taste receptor remains to be established.