Miraculin is a special protein that makes people perceive sour tastes as sweetness instead. At least, for a limited time. Now we know why it works.
Taste adventurers will be interested in a little chemical named miraculin. It was used in West Africa as a way of making some meals more palatable. A small red berry contained trace amounts of the chemical, and before chowing down on something that was certain to be too sour, or stale, people chewed a berry or two, letting the chemical coat their mouths. In 1968 miraculin was first isolated and extracted deliberately from the berry. Since then it's been sold in small tablets that people let dissolve in their mouth.
Recently, scientists have proved exactly how it works. We perceive foods as sweet when they bind to certain receptors on our tongue. Sugar, aspartame, and other sweeteners all bind to the same proteins. Sour foods bind to other receptors. Some thought that miraculin modified the sour food enough for them to bind to the sweetness receptors. In fact, it's the miraculin itself that binds to the receptors itself. It can only do that, however, in a sour environment. Outside of a bath of the acids that make food sour, it doesn't bind to any receptor at all, transforming itself into something completely tasteless.
It's also likely that miraculin blocks the receptor for sourness, at least partially. The combined effect is to turn any hint of sourness in any food sweet. There are any number of foods that would have their tastes significantly altered. It might be interesting to grab some miraculin before a buffet. Not appetizing, but interesting.
Via Scientific American.