We’ve all heard of the five tastes our tongues can detect — sweet, sour, bitter, savory-umami and salty. But the real number is actually six, because we have two separate salt-taste systems. One of them detects the attractive, relatively low levels of salt that make potato chips taste delicious. The other one registers high levels of salt — enough to make overly salted food offensive and deter overconsumption.
Exactly how our taste buds sense the two kinds of saltiness is a mystery that’s taken some 40 years of scientific inquiry to unravel, and researchers haven’t solved all the details yet. In fact, the more they look at salt sensation, the weirder it gets.
Many other details of taste have been worked out over the past 25 years. For sweet, bitter and umami, it’s known that molecular receptors on certain taste bud cells recognize the food molecules and, when activated, kick off a series of events that ultimately sends signals to the brain.
Sour is slightly different: It is detected by taste bud cells that respond to acidity, researchers recently learned.
In the case of salt, scientists understand many details about the low-salt receptor, but a complete description of the high-salt receptor has lagged, as has an understanding of which taste bud cells host each detector.
