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When you chew food, aroma molecules travel from the back of your mouth into your nasal cavity.
This is called retronasal olfaction, and it contributes enormously to what you experience as flavor.
It's different from smelling food through your nostrils before taking a bite.
This is why food can seem strangely flavorless when your nose is congested even though your tongue is still working.
A surprisingly large part of “taste” is actually your brain interpreting smells arriving from inside your mouth.
© Monell Chemical Senses Center