Taste

Encyclopedia of Nursing and Allied Health, 20050229 by R.D. Linda Richards

Definition

Taste is one of the five senses (the others being smell, touch, vision, and hearing) through which all animals interpret the world around them. Specifically, taste is the sense for determining the flavor of food and other substances.

Description

One of the two chemical senses (the other being smell), taste is stimulated through the contact of certain chemicals in substances with clusters of taste bud cells found primarily on the tongue. However, taste is a complex sensing mechanism that is also influenced by the smell and texture of substances. An individual's unique sense of taste is partially inherited, but factors such as culture and familiarity can help determine why one person's favorite food made be hot and spicy while another cannot get enough chocolate.

The primary organ for tasting is the mouth. Clusters of cells called taste buds (because under the microscope they look similar to plant buds) cover the tongue and are also found to a lesser extent on the cheek, throat, and the roof of the mouth. First discovered in the 19th century by German scientists Georg Meissner and Rudolf Wagner, taste buds lie on the bumps and grooves of the tongue (called the papillae) and have hairlike extensions (microvilli) to increase the receptor surface of the cells. Four different pairs of nerves are involved in the tongue, which helps explain in part why the sense of taste is a robust one, and not easily knocked out by disease or trauma.

Genetic and other factors affecting taste

Scientists have also discovered that genetic makeup partially accounts for individual tasting abilities and preferences for specific foods. According to Yale University researchers, some people are genetically programmed to have more taste buds and, as a result, taste more flavors in a particular food. (The number of taste buds varies in different animal species. For example cows have 25,000 taste buds, rabbits 17,000, and adult people approximately 10,000.) In general, a person's ability to taste can lie anywhere in a spectrum from poor to exceptional, with the ability to sense tastes increasing in proportion to the number of taste buds present. The difference in the number of taste buds can be extreme. Researchers have found anywhere from 11 to 1,100 taste buds per square inch in various young people tested. They have also found that women tend to have more taste buds than men and, as a result, are often better tasters. How well people taste greatly affects what they like. Studies at Yale, for example, revealed that children with fewer taste buds who are classified as poor tasters liked cheese more often than exceptional tasters, who experienced a more bitter sensation, probably because of increased sensitivity to the combination of calcium and the milk protein casein found in cheese.

Despite the important role that taste buds play in recognizing flavors, they do not work alone in providing the experience of taste. For example, the amount of naturally occurring salt in saliva varies; with the result that those with less saliva can better taste the saltiness of certain foods than others, who may end up adding salt to get a similar flavor. The smell and texture of foods are also important contributing factors to how people perceive a food to taste and whether or not they like it. Food in the mouth produces an odor that reaches the nose through the nasopharynx (the opening that links the mouth and the nose). Since smell is much more sensitive to odors than taste is to flavors, people often first experience the flavor of a food by its odor. The texture and temperature of food also influences how it tastes. For example, many people would not think of drinking cold coffee, while others will not eat pears because of a dislike for the fruit's gritty texture.

The predilection for certain foods and tastes is not determined merely by biology. Culture and familiarity with foods greatly influence taste preferences. The Japanese have long considered raw fish, or sushi, to be a savory delicacy. Until the 1990s, few Americans would have enjoyed such a repast. As the number of Japanese restaurants grew along with the sushi bars they often contained, so did Americans' familiarity with this delicacy, resulting in a new taste for it.

Function

Taste's primary function is to react to items placed in the mouth. For most foods and substances, saliva breaks down the chemical components which travel through the pores in the papillae to reach the taste buds. These taste buds specialize primarily in processing one of the four major taste groups: sweet, sour, salty, and bitter. Because the four taste groups may not describe all taste sensations, other proposed tastes include metallic, astringent and umami. Umami is the oral sensation stimulated by monosodium glutamate.

Taste occurs when specific proteins in the food bind to receptors on the taste buds. These receptors, in turn, send messages to the brain's cerebral cortex, which interprets the flavor. The actual chemical processes involved for each major taste group vary and involve various mechanisms. For example, salty and sour flavors occur when saliva breaks down sodium or acids, respectively. The chemical constituents of foods that give bitter and sweet tastes are much more difficult to specify due to the large number of chemical components involved.