The sense of smell works by the transmission of electrical signals to the brain via biochemical receptors. In humans, the biochemical receptors are olfactory sensory neurons located in patches of tissue deep inside the nasal cavity.
Odor-producing substances release microscopic particles in the air. The chewing of food releases these aroma particles, which travel through channels that connect the olfactory neurons to the back of the throat. The olfactory sensory neurons detect these particles and respond by transmitting electrical impulses along neural pathways directly to the brain. The brain maintains a record of previously encountered odors and recognizes these signals as particular smells.
Some of these odors are recorded or associated with certain flavors or tastes. When the channels between the throat and nose become blocked by nasal congestion or a cold, it becomes difficult to distinguish certain odors and tastes.