Some interesting insights into how our tongues perceive sour taste have been gained by a new research.
Sour is the sensation evoked by substances that are acidic, such as lemons and pickles. The more acidic the substance, the more sour the taste.
Acids release protons, which were thought to bind to the outside of the cell and opening a pore in the membrane that would allow sodium to enter the cell. Sodium's entry would send an electrical response to the brain, announcing the sensation that we perceive as sour.
But the researchers found that the protons were entering the cell and causing the electrical response directly.
"If we want to know how sour works, we need to measure activity specifically in the sour sensitive taste cells and determine what is special about them that allows them to respond to protons," said Emily Liman, associate professor of neurobiology in the USC College of Letters, Arts and Sciences.
Liman and her team bred genetically modified mice and marked their sour cells with a yellow florescent protein. Then they recorded the electrical responses from just those cells to protons.
The ability to sense protons with a mechanism that does not rely on sodium has important implications for how different tastes interact, Liman speculated.
"It makes sense that nature would have built a taste cell like this, so as not to confuse salty with sour," she said.
In the future, the research may have practical applications for cooks and the food industry.
"Once we've understood the nature of the molecules that sense sour, we can start thinking about how they might be modified and how that might change the way things taste. We may also find that the number or function of these molecules changes during the course of development or during aging."
The finding is to be published this week in the Proceedings of the National Academy of Sciences (PNAS) journal.