The Hidden Link Between Smell and Taste

Pinch your nose shut and eat a jellybean — most people, tested this way, cannot tell a lemon one from an orange one, and sometimes cannot even tell they’re eating a jellybean at all rather than plain sugar. The tongue, on its own, is a surprisingly blunt instrument: it distinguishes only five qualities — sweet, sour, salty, bitter, and umami — nothing that would explain the difference between a strawberry and a raspberry.

What we call flavor is mostly smell, arriving by the back door. As we chew, aroma molecules rise up the throat into the nasal cavity from behind, reaching the same olfactory receptors that a sniff reaches from the front — a route physiologists call retronasal olfaction, as opposed to the orthonasal kind used for ordinary smelling. It is why food turns bland and interchangeable during a bad cold: the tongue still works perfectly, but the passage behind it is blocked.

Wine tasting makes the point almost embarrassingly well. Trained tasters describe leather, violets, wet stone, and black cherry in a glass that, chemically speaking, offers the tongue only sourness, a little sweetness, and tannin’s bitterness — everything else is retronasal smell, reconstructed by the brain into something we insist on calling taste.