The sense of taste, one of the five major senses, is defined based on anatomy. In mammals, it is the sense subserved by taste receptor cells located primarily on taste buds in the oral cavity. These taste receptor cells are innervated by branches of the seventh, ninth, and tenth cranial nerves that synapse first in the brainstem prior to sending messages to other parts of the brain (Breslin and Spector, 2008).
Most investigators agree that the sense of taste is composed of a small number of primary or basic taste qualities, usually consisting of sweet, sour, salty, bitter, and savory or umami (Bachmanov and Beauchamp, 2007). It is thought that these specific classes or categories of taste evolved to help the animal solve two of its most primary problems: the identification and ingestion of nutrients and the avoidance of poisons. As a presumed consequence of these dedicated critical functions, positive or negative responses to taste compounds (tastants) are often genetically programmed. For example, sweet tastants are generally innately liked and ingested by animals that consume plants (herbivores and omnivores—some carnivores, such as cats, do not detect sweet compounds) (Li et al., 2005). In contrast, bitter tastants are generally disliked and avoided, since many are toxic (Breslin and Spector, 2008).
Virtually all foods and beverages impart sensations in addition to taste. For example, a complex food such as soup not only has taste properties (e.g., it is salty, sour, or sweet) but also has volatile compounds that give it its specific identity (e.g., pea soup compared to potato soup), and it may also have burning properties, such as those caused by hot peppers. These sensory properties are conveyed by the sense of smell (cranial nerve 1), experienced mainly through the retronasal route—from the throat up through the nasal passages and up to the olfactory receptors in the upper regions of the nasal cavity—and the sense of chemesthesis (Green et al., 1990) or irritation (cranial nerve 5), respectively. In common parlance, the entire sensation elicited by this food is called its “taste.” However, most scientists would instead use the term “flavor” to refer to this total sensation, and that is how it will be used here. It should be noted that many also include the texture of a food as a component of flavor. Taste molecules such as salt can influence flavor in many ways, some of which are described below.
Although this chapter focuses on how the taste imparted by salt influences food palatability, it needs to be emphasized that the other chemi-