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Published:  23 July, 2008

By Jamie Goode

Scientists have identified a new taste receptor that could change our understanding of wine tasting. The results, published in leading scientific journal Nature, pinpoint for the first time a receptor enabling humans to taste amino acids such as monosodium glutamate, the widely used flavour enhancer. The existence of a fifth taste, known by the Japanese term umami', had been suspected for a while. However, in the absence of a receptor for amino acids on the tongue, there was some debate about whether it might simply be a combination of the other tastes. This new research by US scientists Charles Zuker and Charles Ryber shows conclusively that umami is one of the basic tastes, along with sweet, salty, bitter and sour. Zuker and Ryber studied a group of receptors in taste cells known as T1R'. They showed that when different T1R genes are expressed in combination in taste cells, they enable the detection of specific tastes: whereas T1R3 and T1R2 together produce a receptor for sweet tastes, T1R1 and T1R3 in tandem produce a receptor that recognises amino acids. Wine contains some 1-4 grams per litre of amino acids, which according to Zuker (who is a wine lover) would robustly activate the amino acid receptor'. However, he told Harpers: Because the perception of wine reflects the interaction of so many players in such a complex mixture, we cannot assign a value to the contribution of the umami receptor versus the sweet, sour, bitter and salty receptors.' In theory, it should be possible to test the impact of amino acids on the taste of wine simply by changing their levels. But, Zuker added: I do not believe that this is a good experiment, since it is the interplay of the various taste modalities that produces the final taste.' An increased understanding of the way that human taste works raises the possibility that winemakers could use manipulations that would help them design wines to taste better'.