A scientific paradox linking artificial sweeteners with a sensory experience in which plain water takes on a sweet taste has helped researchers better understand how humans detect sweet taste, according to an advance online publication in Nature.
Scientists from the Monell Chemical Senses Center, Philadelphia, described how certain artificial sweeteners, including sodium saccharin and acesulfame-K, inhibit sweet taste at high concentrations. They found that taste perception switches back to sweetness when these high concentrations are rinsed from the mouth with water, resulting in the after-taste experience known as sweet "water taste."
"These findings will open doors for tweaking the sweet taste receptor and finding new sweeteners and inhibitors that can be used both by [the] food industry and in medicine," said Paul A.S. Breslin, PhD, a Monell geneticist and senior author.
Lead author Veronica Galindo-Cuspinera, PhD, explained that saccharin, which is used commonly at low concentrations as an artificial sweetener, loses its initially sweet taste when tasted at high concentrations. She observed that strong sweetness returned when the high concentrations of saccharin were rinsed from the mouth with water.
The researchers discovered that high concentrations of saccharin inhibit the sweetness of any other sweetener tasted at the same time.
Testing a variety of compounds, they found that any sweetener that elicits sweet "water taste" also acts as a sweet taste inhibitor.
To understand how sweet "water taste" compounds could act both as a sweetener and as a sweet inhibitor, collaborators Marcel Winnig, Bernd Bufe and Wolfgang Meyerhof, German Institute of Human Nutrition, Nuthetal, Germany, conducted a series of molecular studies using cultured cells expressing the human sweet taste receptor.
Findings revealed that the cellular responses directly parallel the human perceptual responses.
"The phenomenon of sweet water taste is the direct result of releasing the receptor from inhibition," said Dr. Galindo-Cuspinera. "It is rare to find so complete a molecular explanation for a complex perceptual phenomenon," she said. "We can now use sweet water taste as a predictor for potential sweet inhibitors."
Sweet inhibitors are used by the food industry to counteract the undesirable high sweetness that results from replacing fats with sweet carbohydrates in reduced-fat products, such as snack foods and salad dressings.
"The extremely close parallels between the behavior of the human sweet taste receptor and the perceptual phenomenon are remarkable," said Dr. Breslin. "This two-site model should enable a more complete understanding of human sweet taste perception, leading directly to studies of how to stimulate, manipulate, enhance, inhibit and create synergy of sweet taste."
This study was funded by the National Institutes of Health and the German Science Foundation.
