The tongue is covered with many little bumps called papillae. Taste buds are found in the walls of papillae and the grooves surrounding them. Each taste bud contains anywhere from 50 to 150 taste receptor cells. 

Microvilli extend from taste receptor cells

and protrude through an opening (taste pore) into the mouth. 

These microvilli come in contact with substances in the mouth that can be tasted, also known as tastants.

Tastants interact with taste receptor cells through a number of different mechanisms to depolarize the cells. 

When taste cells are depolarized, they release neurotransmitters that stimulate sensory neurons that travel in cranial nerves VII, IX, and X. 

These neurons terminate on neurons in the nucleus of the solitary tract in the medulla then continue on to the thalamus. 

Taste information is sent to the gustatory cortex, ( ocated on the border between the anterior insula and the frontal operculum). 

This information encodes for basic tastes, such as sweet, salty, sour, bitter, and savory or umami. 

However, the actual flavour of a food---which is what we typically define as taste---is created by a combination of taste and olfactory (smell) information.

Sweetness

Produced by the presence of sugars, some proteins, and other substances.

Detected by G protein-coupled receptors T1R2+3 (heterodimer) and T1R3 (homodimer).

Saltiness

Saltiness is a taste produced best by the presence of cations (such as Na+, K+or Li+) 

Directly detected by cation influx into glial like cells via leak channels causing depolarisation of the cell.

Sourness

Sourness is acidity and is also sensed using ion channels. 

Undissociated acid diffuses across the plasma membrane of a presynaptic cell, where it dissociates in accordance with Le Chatelier's principle. 

The protons that are released then block potassium channels, which depolarise the cell and cause calcium influx. 

Bitterness

Current research suggests TAS2Rs (taste receptors, type 2, also known as T2Rs) such as TAS2R38 are responsible tasting bitter substances. 

Savouriness

The amino acid glutamic acid is responsible for savouriness, but some nucleotides (inosinic acid and guanylic acid) can act as complements.

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FOOD TOURISM: Explore the world with your taste buds

Chinese philosopher Confucius was quoted as saying “Everyone eats and drinks, but few appreciate taste.” Food and drink serve not only as a means of providing nourishment for our bodies, but also as pleasure. The pleasures a person has when experiencing certain flavors can often be disregarded, much like Confucius suggested. Overlooked, as well, are the complex actions occurring within the body when we experience and interpret taste. 

Though we begin with a Chinese quote about taste we shall continue with a Portuguese proverb, “For each mouth, a different soup.” It is not uncommon for people to have noticed that what tastes good to one person does not necessarily taste good for the next. The biological processes for taste all work in the same fashion yet perception and preference of taste can vary by individual. It could make sense then to conclude that something in an individual’s environment may impact their taste preference. Could the regional cooking create taste preference based upon culture? The sensory system that handles taste, mixes with smell, and creates a perception of flavor; in addition to possible cultural differences in preference of taste is the topic of this paper.

Taste perception within the gustatory system begins when food is placed within the mouth. Solid foods are broken down into molecules that can be dissolved in saliva. From this point the physiology of the gustatory system becomes very important. The tongue is covered with bumpy structures called papillae which contain taste buds. Taste buds, which create signals that are relayed to the brain by taste nerves, have taste receptor cells. These taste receptor cells can only receive certain molecules, but when it makes contact with a molecule it can communicate with it creates an action potential. This action potential is what sends information to the cranial nerves in the brain. 

Sensory information about taste does not stop at the cranial nerves. The Medulla and the thalamus are additional areas of the brain in which the gustatory information travels through on its way to the cortex. The first part of the cortex that receives taste information is the insular cortex. The insular cortex then projects information to its final stop, the orbitofrontal cortex. The orbitofrontal cortex has multimodal (more than one process) neurons which mean this area may be used in integration of temperature, touch, smell, and well as taste. 

The current consensus is that there are four basic tastes: sweet, salty, sour, and bitter. Liking and disliking of these four flavors is hardwired from birth. The four mentioned tastes help humans detect nutrients as well as “antinutrients.” Bitter and sour tastes help keep humans away poisons and acidic substances respectively. Sweet and salty tastes attract us to sugar and sodium, two types of foods components that the humans need. Not only do these four tastes serve in theory these guide humans to which specific nutrients we need via cravings. The specific hunger theory states that our body communicates nutrient deficiency by creating cravings. Several research studies were conducted to examine this theory but it was Paul Rozin (1967 as cited in (Wolfe et al., 2008) that concluded that the specific hunger theory only worked in the case of sweet and salty cravings. 

We have seen that we can crave items our body needs, and that we are hardwired to enjoy certain tastes, but what creates specific likes and dislikes of foods? It is a combination of hardwired and learned likes and dislikes that create cognitive reactions which compel us to like or dislike foods. The hardwired force to like a one of the four basic tastes combines with a learned preference for certain retronasal smells (odors that are perceived when food in the mouth is chewed or swallowed) to determine our affect towards certain foods. Additionally, the gastrointestinal tract plays a role in the learning of food preferences by stimulation of chemoreceptors (receptors that create action potentials) when certain foods are ingested. The stimulations of these receptors and the brain are what play key roles in our conditioned food preferences.

As suggested by the earlier Portuguese proverb there is genetic variation in taste experience. One particularly fascinating discovery was made by Arthur Fox (1931 as cited in (Wolfe et al., 2008) who accidently discovered the inability for certain people to taste bitterness in PTC crystals that other people tasted. He called people who could taste the bitterness “tasters” and those who could not “nontasters.” Further research by Fischer suggested that due to tasters ability to detect bitterness easier that their eating patterns would be more selective containing less vegetables than those of nontasters due to their bitter compound (Wolfe et al., 2008). Some clinical implications of the commonly reduced vegetable intake of tasters include elevated risk of colon cancer. Tasters, on the other hand, would be able to find vegetables more tolerable due to their inability to detect the bitterness tasters did. A third class of taster, a “supertaster,” was found to have the ability to detect the most intense taste sensations. A pleasant consequence of “super tasting” ability is the lowered risk of cardiovascular disease. This lowered cardiovascular risk is due to supertasters reaction to highly fatty foods which can produce unpleasant sensations from their intake. (Wolfe et al., 2008)

We now have a basic understanding of taste variation and preference in individuals but what about cultures as a whole? Mark Twain was quoted as saying “Foreigners cannot enjoy our food, I suppose, any more than we can enjoy theirs. It is not strange; for tastes are made, not born.” What Twain is suggesting is that cultural food preference and enjoyment does vary by region. One particular research that studied cultural differences in taste occurred in 1975 Indian laborers from the Karnataka region in India (Moskowitz, V. Kumariah, K. N. Sharma, H. L. Jacobs, & S. D. Sharma, 1975). This study notes that in the Western world sweetness is a pleasing taste while bitter and sour tastes are displeasing. When examining the diets of illiterate Indian laborers whose diet consists of about 1,200 – 1,500 calories a day, researchers noted the occurrences of bitter and sour foods that are ingested on a regular basis. This finding showed that daily diets of Indian laborers emphasized more sour tastes than Western diets. Precautions were taken due to laborers illiteracy to ensure the comprehensive completion of pleasantness of tastes twice a day; once after a 14 hour fast and before breakfast and once again after lunch. When tasting various substances the preferences for sour and bitter tastes differed in preference from Western populations. One specifically interesting finding was that as the concentration of citric acid (sourness) was increased so did the related pleasantness according to the laborers. Additional findings included the rating of pleasantness of quinine (bitterness) in low doses. These findings differ from Western subjects ratings of similar substances. One commonality between Western and Karnataka subjects was the ratings of pleasantness of salty and sweet flavors.  One explanation of the differences in taste preference is each group’s dietary history. Since tamarind is commonly eaten by the Karnataka laborers their ratings of pleasantness of sour tastes may reflect an actual preference for sourness.

Research on national and sub-cultural consumption is another study that aims to examine the behavioral and regional differences in food preference. One such study was conducted by Wright, Nancarrow and Kwok (2001) where influence of culture was examined in terms of food preference in order to find a link for consumer research. Wright claims that culture has always been connected to food preference. Specifically, Wright claims that food preferences are a product of “geographical, historical, and economic context” (Len Tiu Wright, Clive Nancarrow, & Pamela M.H. Kwok, 2001). Influence of other cultures upon one particular culture will also influence food preferences compared to countries that were isolated regions. 

Religion is also said to influence food preferences according to Wright. An example of religion impacting food preference stated in Wright’s study is Britain’s Protestant movement which aided in the Industrial Revolution. Soon after this change food began to be seen less as a “pleasure” and more as a substance for providing fuel for the body. As food became more of a necessity and dwindled in quantity many diets in Britain degraded as well to the extent where some would often sustain on tea and bread.

Supporting the cultural influences of tastes Wright quotes Fowler in saying that tastes are created over generations through social construct (Len Tiu Wright et al., 2001). Other influences of taste differences based upon culture include income. Lower wage earners tend to enjoy the feeling of fullness and thus prefer sweet flavored foods most. The “sweet tooth” phenomenon is said to be passed down generationally in working class families. As you can see, not only your family, but your area and culture as whole can impact a person’s taste preference and eating behaviors.

French painter Maurice de Vlaminck once said, “Good painting is like good cooking; it can be tasted, but not explained.” In an effort to explain taste and its acquisition I have covered the physiological anatomy of the gustatory system, theories about the influence of taste, research the explores taste and taste differences in culture, cognitive reactions to liked and disliked tastes, and how behaviors of those around us and our region can influence taste preference. These items, however, get us no closer to the appreciation of taste. I can appreciate the complexity of the systems that help create taste and how the world around me can influence my taste, but actually really appreciating taste is more than what I have referenced within this paper. 

Perception, in this case the perception of taste, is one of the ‘hard issues” that are attempted to be explained through the study of sensation and perception. When I sit down to a meal and take a bite of a chicken, knowing that as I chew food smells are creating a retronasal olfactory sensation does not help me appreciate the taste of food, rather, I appreciate the complex system that is allowing me to taste. When my mouth salivates when cutting lemons to eat as a snack I do not recall that as a human I am hardwired against sour foods due to their acidic content (well, maybe I will now). I am recalling my love of the sour, acidic taste of lemons sprinkled with salt and chili (bitterness) that I enjoy. The fact that I am enjoying such a treat and the social and cultural influences that brought about my enjoyment of these items. 

I began this paper with the intent of explaining the gustatory system as a way to gain appreciation for taste of food by describing the complicated system that brings about the perception of flavor and enjoyment to a person. Yet as conclude my writing I have come to the realization that this explanation does not bring about appreciation of a system whose perceptions vary from person to person as flavor manifests itself on our tongues and in our minds. I can compare taste to many different things in life; however, the perception of taste is something that is indescribable. 

References

Len Tiu Wright, Clive Nancarrow, & Pamela M.H. Kwok. (2001). Food taste preferences and cultural influences on consumption. British Food Journal, 103(5), 348 - 357.

Moskowitz, H. W., V. Kumariah, K. N. Sharma, H. L. Jacobs, & S. D. Sharma. (1975). Cross-Cultural Differences in Simple Taste Preferences. Science, New Series, 190(4220), 1217 - 1218.