
The vast majority of flavor sensations do not originate in the mouth,
where taste receptors are, but in the nasal passages, which contain
smell, or olfactory, receptors. Your brain knows only from your tongue
whether a stimulus is salty, sour, sweet, bitter or meaty, and must rely
on the olfactory sensors picking up gas particles from foods in the
mouth to discern the nuances of individual tastes.
Without your nose, you have no hope of telling what is really in your
mouth - something you may have observed while suffering from a stuffy
nose. Do some experiments at home by biting an apple normally and then
biting the same apple with an onion under your nose. When you chomp on
the same apple while you smell an onion, you will have a very different
experience.