Why is your sense of taste impaired when you only breathe through your mouth and not your nose?

Smell Problem effect: The tongue can detect only sweet, salty, sour, and bitter tastes. Much of what is perceived as "taste" is actually smell. People who have taste problems often have a smell disorder that can make it hard to identify a food's flavor. Flavor is a combination of taste and smell. Taste problems can be caused by anything that interrupts the transfer of taste sensations to the brain, or by conditions.

Smell not taste: Taste is sensed through the mouth. Example is sweet. The flavor of food derives mostly from smell . The smell sensors are located in the nasal roof.