ABSTRACT
Flavor, a powerful determinant of human consummatory behavior throughout the life span, is a product of several sensory systems, most notably those of taste and smell. The perceptions arising from these two senses are often confused and misappropriated, with such sensations as vanilla, meat sauce, fish, chocolate, and coffee being erroneously attributed to the taste system per se. In fact, taste sensations, mediated by taste buds distributed throughout the oral cavity (see Chapter 32), are largely those of sweet, sour, bitter, salty, and perhaps metallic and savory (e.g., the “umami” taste of monosodium glutamate). Smell sensations, on the other hand, encompass thousands of diverse qualities, some of which are noted above. The receptors for the olfactory system, located high in the nasal chambers, are stimulated not only during inhalation (orthonasal route), but during suckling in infants and deglutition in adults, when molecules reach the receptors by passing from the oral cavity through the nasal pharynx (retronasal route) (Fig. 1). It is this retronasal stimulation arising from the molecules of foodstuffs that leads to the predominant flavor sensations. As noted in detail in several chapters of this volume (e.g., Chapters 2-6), olfactory sensations result from the activation of 1000 or more distinct types of chemical receptors located on millions of receptor cells lining the upper recesses of the nasal cavity.
