Serious Eats
Calcium: The Tongue's Sixth 'Taste' Discovered
Your tongue might be able to taste calcium, according to scientists like Michael Tordoff, the behavioral geneticist at the Monell Chemical Senses Center in Philadelphia. And how does it taste? "Calcium-y," Tordoff said. "There isn't a better word for it."
A sour bitterness is the best description, which could explain why certain people don't like collard greens, bok choy, kale, or bitter melon. They are all calcium-rich vegetables.