Stevia is regarded as a healthy alternative to sugar. Yet there are drawbacks to the Stevia products recently approved as sweeteners by the European Union. One of these is a long-lasting bitter after-taste. Scientists at Technische Universitaet Muenchen (TUM) and the German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE) have now identified the receptors on the human tongue mediating the bitter sensation (Journal of Agricultural and Food Chemistry).
The human tongue has just one receptor type for detecting sweetness but about25 different ones for bitter flavors. Scientists at Technische Universitaet Muenchen (TUM) and the German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE) have now identified the two receptors, hTAS2R4 and hTAS2R14, that detect the bitter after taste of Stevia.
Prof. Thomas Hofmann (Chair of Food Chemistry and Molecular Sensory Science at TUM) and Wolfgang Meyerhof (German Institute of Human Nutrition Potsdam-Rehbruecke) investigated nine Steviol glycosides responsible for the intensive sweet taste of Stevia plant extracts. Sensory tests combined with cell experiments in vitro revealed that the structure of glycoside molecules plays a key role in determining sweetness or bitterness in Stevia. These new findings could help minimize the bitter taste of Stevia products at an early stage in production processes. ”They could open the way for selective cultivation measures or targeted purification during the development of Stevia products, enabling manufacturers to focus on the sweetest candidates,” confirms TUM scientist Thomas Hofmann.
Caroline Hellfritsch, Anne Brockhoff, Frauke Stähler, Wolfgang Meyerhof, Thomas Hofmann: Human Psychometric and Taste Receptor Responses to Steviol Glycosides, Journal of Agricultural and Food Chemistry, May 2012