When you think about your favorite foods, you can almost taste them. But regard- less of whether you swoon over a grilled steak, chow mein with mustard greens, or a spicy salsa, your appreciation of a certain food depends on more than taste alone. As you likely know from having had a cold, food seems tasteless when your nose is really stuffed up. This lack of perception happens because our sense of taste relies heavily on our sense of smell. Together, taste and smell produce the experience of flavor. In fact, flavor is based more on smell than on taste. This perceptual experi- ence does not take place in your mouth and nose, however. Like seeing and hearing, experiencing flavor occurs in your brain.
Receptors in Our Taste Buds Detect Chemical Molecules The sense of taste is also called gustation. Gustation has an adaptive function. In other words, taste is related to survival. If something you eat tastes really bad, you are likely to spit it out. This response is adaptive, because the job of taste is to keep poisons out of the digestive system while allowing good food in.
FROM THE MOUTH TO THE BRAIN Suppose you taste a lemon (Figure 5.21). The physical stimulus that causes you to taste this food consists of chemical molecules that dissolve in saliva (see Figure 5.21, Step 1). The taste receptors are the sensory receptors that detect the chemical molecules. They are located in the taste buds (see Figure 5.21, Step 2). On the tongue, the taste buds reside in tiny, mushroom-shaped structures called papillae. But the taste buds are also spread throughout the mouth and throat. Most individuals have approximately 8,000 to 10,000 taste buds.
Food, fluid, or any other substance (e.g., dirt) will stimulate the taste buds. At that point, the taste receptors transduce the sensory input into action potentials (see Figure 5.21, Step 3). The taste information is sent to other brain regions through a set of nerves, primarily the facial nerve (see Figure 5.21, Step 4). After processing by the thalamus, the information is further processed in the gustatory cortex.
FIvE MAIN TASTES Like the other senses, taste involves a nearly infinite vari- ety of perceptions. These perceptions arise from the activation of unique combina- tions of receptors. Scientists once believed that different regions of the tongue are more sensitive to certain tastes, but we now know that the different taste buds are spread relatively uniformly throughout the tongue and mouth (Lindemann, 2001). Every taste experience is composed of a mixture of five basic qualities: sweet, sour, salty, bitter, and umami (Japanese for “savory” or “yummy”; pronounced “oo-MOM-ee”). Umami is the most recently recognized taste sensation (Krulwich, 2007). If you have eaten foods such as meat, cheese, or mushrooms, you may have noticed how they seem to be bursting with flavor. If so, you have experienced umami. Researchers are still investigating how the cells in the taste buds lead to perception of all five of these taste qualities.
Some people experience taste sensations intensely. This trait is determined largely by genetics. These individuals, known as supertasters, are highly aware of flavors and textures and are more likely than others to feel pain when eating very spicy foods (Bartoshuk, 2000). Supertasters have nearly six times as many taste buds as normal tasters. The more taste buds you have, the more intense your taste experiences will be.
Although it might sound enjoyable to experience intense tastes, many super- tasters are especially picky eaters because particular tastes can overwhelm them. When it comes to sensation, more is not necessarily better. Being a supertaster may also affect health. Supertasters tend to avoid bitter-tasting foods, which they find extremely distasteful. This avoidance may put the supertasters at risk for some cancers that bitter foods may protect against (Basson et al., 2005). The upside is that supertasters also dislike the taste of fatty, sugary foods, so they tend to be thin and may have a lower risk of cardiovascular disease. You can take the test in Try It Yourself, on p. 182, to see if you are a supertaster.
TASTE PREFERENCE Do you love or hate anchovies? Each of us has individ- ual taste preferences. These preferences come partly from our different numbers of taste receptors. The same food can actually taste different to different people, because the sensation associated with that food differs in their mouths. The texture of food also affects taste preferences: Whether a food is soft or crunchy, creamy or granular, tender or tough affects perception of the sensory experience. Another factor is whether the food causes discomfort, as can happen with spicy chilies. But cultural factors influence taste preferences as well.