Your nose does the tasting

Two doors into your nose

Smell reaches you by two routes. Sniffing over the cup is orthonasal smell — the front door. A sip sends aroma up the back of your throat to the same nose.

• front route · sniffing: Air comes in through your nostrils carrying aroma off the cup. Cuppers call the dry-grounds version the fragrance.
• back route · sipping: A sip pushes aroma up behind your palate to the same sensors. This is the route that feels like taste.
• mouth · the five tastes: Sweet, sour, salty, bitter and umami are picked up here, all around your mouth — and nothing else is.

Filed under taste

That back route is retronasal smell, and it fires while the coffee is still in your mouth — so your brain files it under “taste”. It isn’t taste: it’s your nose, by the tradesmen’s entrance.

Close the door

Block the nose and watch what leaves. A sip is still hot, bitter, a little sour, with some weight on the tongue; the aroma arrows shut off.

Why a cold flattens food

Your nose is blocked by a cold. Why does dinner taste of almost nothing?

Answer: Odours can’t reach your smell sensors. Odours can’t get through, so what’s left is the five tastes and the texture. The nose was doing most of the work all along.

The nose-pinch test

Pinch your nose, chew a jelly bean and try to name the flavor. Sweet, perhaps sour, and little else. Let go, and the flavor arrives all at once, like a guest kept waiting.

Five tastes, and the rest

Which sense picks each one up?

• taste
  • sweet
  • sour
  • salty
  • bitter
  • umami
• smell
  • blueberry
  • jasmine
  • caramel

Sweet, sour, salty, bitter and umami are tastes — umami is the savoury one. Blueberry, jasmine and caramel are smells.

Even the sweetness

Researchers argue about the exact share, but agree the nose does most of the work. Even black coffee’s sweetness may be largely aroma: a UC Davis study found no simple sugars in drip brews anyone could taste.

Sniff short

Smell the dry grounds, then the brewed cup, in short bursts. A nose parked over one smell soon tires of it and reports less.

Then slurp, and breathe out

Slurp, swallow, and breathe out through your nose.

You swallow, then breathe out through your nose. What does the exhale do?

Answer: Carries aroma past your sensors from behind. It carries aroma up past your smell sensors from behind — the easiest way to catch what a coffee tastes “of”.