Taste and smell are sensations that result when specialized nerve receptors in the mouth and nose detect molecules. The ability to detect molecules in this manner referred to as chemoreception.
A taste is recognized by the brain after specialized nerves in the throat and tongue detect chemical molecules within ingested liquids or solids. In man, there are 4 basic classes of tastes: sweet, sour, bitter, and salt.
A smell is recognized by the brain after specialized nerves in the passages of the nose detect chemical molecules within the inhaled air.
The flavor of food is largely a combination of taste and smell
sensations. (The consistency and temperature of foods also play a
role in determining their "taste.")
For more, please visit the MedicineNet.com Nutrition Center.