peppery or hot (from spices). pungency (also spiciness or hotness) substances such as ethanol and capsaicin cause a burning sensation by inducing a trigeminal nerve reaction together with normal taste reception. the sensation of heat is caused by the food's activating nerves that express trpv1 and trpa1 receptors. some such plant-derived compounds that provide this sensation are capsaicin from chili peppers, piperine from black pepper, gingerol from ginger root and allyl isothiocyanate from horseradish. the piquant ("hot" or "spicy") sensation provided by such foods and spices plays an important role in a diverse range of cuisines across the world—especially in equatorial and sub-tropical climates, such as ethiopian, peruvian, hungarian, indian, korean, indonesian, lao, malaysian, mexican, new mexican, pakistani, singaporean, southwest chinese (including sichuan cuisine), vietnamese, and thai cuisines. this particular sensation, called chemesthesis, is not a taste in the technical sense, because the sensation does not arise from taste buds, and a different set of nerve fibers carry it to the brain. foods like chili peppers activate nerve fibers directly; the sensation interpreted as "hot" results from the stimulation of somatosensory (pain/temperature) fibers on the tongue. many parts of the body with exposed membranes but no taste sensors (such as the nasal cavity, under the fingernails, surface of the eye or a wound) produce a similar sensation of heat when exposed to hotness agents. coolness some substances activate cold trigeminal receptors even when not at low temperatures. this "fresh" or "minty" sensation can be tasted in peppermint, spearmint and is triggered by substances such as menthol, anethol, ethanol, and camphor. caused by activation of the same mechanism that signals cold, trpm8 ion channels on nerve cells, unlike the actual change in temperature described for sugar substitutes, this coolness is only a perceived phenomenon. numbness both chinese and batak toba cooking include the idea of 麻 (má or mati rasa), a tingling numbness caused by spices such as sichuan pepper. the cuisines of sichuan province in china and of the indonesian province of north sumatra often combine this with chili pepper to produce a 麻辣 málà, "numbing-and-hot", or "mati rasa" flavor. typical in northern brazilian cuisine, jambu is an herb used in dishes like tacacá. these sensations, although not taste, fall into a category of chemesthesis. astringency some foods, such as unripe fruits, contain tannins or calcium oxalate that cause an astringent or puckering sensation of the mucous membrane of the mouth. examples include tea, red wine, or rhubarb. other terms for the astringent sensation are "dry", "rough", "harsh" (especially for wine), "tart" (normally referring to sourness), "rubbery", "hard" or "styptic". metallicness a metallic taste may be caused by food and drink, certain medicines or amalgam dental fillings. it is generally considered an off flavor when present in food and drink. a metallic taste may be caused by galvanic reactions in the mouth. in the case where it is caused by dental work, the dissimilar metals used may produce a measurable current. some artificial sweeteners are perceived to have a metallic taste, which is detected by the trpv1 receptors. many people consider blood to have a metallic taste. a metallic taste in the mouth is also a symptom of various medical conditions, in which case it may be classified under the symptoms dysgeusia or parageusia, referring to distortions of the sense of taste, and can be caused by medication, including saquinavir, zonisamide, and various kinds of chemotherapy, as well as occupational hazards, such as working with pesticides. fat taste recent research reveals a potential taste receptor called the cd36 receptor. cd36 was targeted as a possible lipid taste receptor because it binds to fat molecules (more specifically, long-chain fatty acids), and it has been localized to taste bud cells (specifically, the circumvallate and foliate papillae). there is a debate over whether we can truly taste fats, and supporters of human ability to taste free fatty acids (ffas) have based the argument on a few main points: there is an evolutionary advantage to oral fat detection; a potential fat receptor has been located on taste bud cells; fatty acids evoke specific responses that activate gustatory neurons, similar to other currently accepted tastes; and, there is a physiological response to the presence of oral fat. although cd36 has been studied primarily in mice, research examining human subjects' ability to taste fats found that those with high levels of cd36 expression were more sensitive to tasting fat than were those with low levels of cd36 expression; this study points to a clear association between cd36 receptor quantity and the ability to taste fat. other possible fat taste receptors have been identified. g protein-coupled receptors gpr120 and gpr40 have been linked to fat taste, because their absence resulted in reduced preference to two types of fatty acid (linoleic acid and oleic acid), as well as decreased neuronal response to oral fatty acids. monovalent cation channel trpm5 has been implicated in fat taste as well, but it is thought to be involved primarily in downstream processing of the taste rather than primary reception, as it is with other tastes such as bitter, sweet, and savory. proposed alternate names to fat taste include oleogustus and pinguis, although these terms are not widely accepted. the main form of fat that is commonly ingested is triglycerides, which are composed of three fatty acids bound together. in this state, triglycerides are able to give fatty foods unique textures that are often described as creaminess. but this texture is not an actual taste. it is only during ingestion that the fatty acids that make up triglycerides are hydrolysed into fatty acids via lipases. the taste is commonly related to other, more negative, tastes such as bitter and sour due to how unpleasant the taste is for humans. richard mattes, a co-author of the study, explained that low concentrations of these fatty acids can create an overall better flavor in a food, much like how small uses of bitterness can make certain foods more rounded. a high concentration of fatty acids in certain foods is generally considered inedible. to demonstrate that individuals can distinguish fat taste from other tastes, the researchers separated volunteers into groups and had them try samples that also contained the other basic tastes. volunteers were able to separate the taste of fatty acids into their own category, with some overlap with savory samples, which the researchers hypothesized was due to poor familiarity with both. the researchers note that the usual "creaminess and viscosity we associate with fatty foods is largely due to triglycerides", unrelated to the taste; while the actual taste of fatty acids is not pleasant. mattes described the taste as "more of a warning system" that a certain food should not be eaten. there are few regularly consumed foods rich in fat taste, due to the negative flavor that is evoked in large quantities. foods whose flavor to which fat taste makes a small contribution include olive oil and fresh butter, along with various kinds of vegetable and nut oils. heartiness kokumi (/koʊkuːmi/, japanese: kokumi (コク味) from koku (こく)) is translated as "heartiness", "full flavor" or "rich" and describes compounds in food that do not have their own taste, but enhance the characteristics when combined. alongside the five basic tastes of sweet, sour, salt, bitter and savory, kokumi has been described as something that may enhance the other five tastes by magnifying and lengthening the other tastes, or "mouthfulness".: 290 garlic is a common ingredient to add flavor used to help define the characteristic kokumi flavors. calcium-sensing receptors (casr) are receptors for kokumi substances which, applied around taste pores, induce an increase in the intracellular ca concentration in a subset of cells. this subset of casr-expressing taste cells are independent from the influenced basic taste receptor cells. casr agonists directly activate the casr on the surface of taste cells and integrated in the brain via the central nervous system. a basal level of calcium, corresponding to the physiological concentration, is necessary for activation of the casr to develop the kokumi sensation. calcium the distinctive taste of chalk has been identified as the calcium component of that substance. in 2008, geneticists discovered a calcium receptor on the tongues of mice. the casr receptor is commonly found in the gastrointestinal tract, kidneys, and brain. along with the "sweet" t1r3 receptor, the casr receptor can detect calcium as a taste. whether the perception exists or not in humans is unknown. temperature temperature can be an essential element of the taste experience. heat can accentuate some flavors and decrease others by varying the density and phase equilibrium of a substance. food and drink that—in a given culture—is traditionally served hot is often considered distasteful if cold, and vice versa. for example, alcoholic beverages, with a few exceptions, are usually thought best when served at room temperature or chilled to varying degrees, but soups—again, with exceptions—are usually only eaten hot. a cultural example are soft drinks. in north america it is almost always preferred cold, regardless of season. starchiness a 2016 study suggested that humans can taste starch (specifically, a glucose oligomer) independently of other tastes such as sweetness, without suggesting an associated chemical receptor. nerve supply and neural connections this diagram linearly (unless otherwise mentioned) tracks the projections of all known structures that allow for taste to their relevant endpoints in the human brain. the glossopharyngeal nerve innervates a third of the tongue including the circumvallate papillae. the facial nerve innervates the other two thirds of the tongue and the cheek via the chorda tympani. the pterygopalatine ganglia are ganglia (one on each side) of the soft palate. the greater petrosal, lesser palatine and zygomatic nerves all synapse here. the greater petrosal, carries soft palate taste signals to the facial nerve. the lesser palatine sends signals to the nasal cavity; which is why spicy foods cause nasal drip. the zygomatic sends signals to the lacrimal nerve that activate the lacrimal gland; which is the reason that spicy foods can cause tears. both the lesser palatine and the zygomatic are maxillary nerves (from the trigeminal nerve). the special visceral afferents of the vagus nerve carry taste from the epiglottal region of the tongue. the lingual nerve (trigeminal, not shown in diagram) is deeply interconnected with the chorda tympani in that it provides all other sensory info from the anterior ⅔ of the tongue. this info is processed separately (nearby) in the rostal lateral subdivision of the nucleus of the solitary tract (nst). nst receives input from the amygdala (regulates oculomotor nuclei output), bed nuclei of stria terminalis, hypothalamus, and prefrontal cortex. nst is the topographical map that processes gustatory and sensory (temp, texture, etc.) info. reticular formation (includes raphe nuclei responsible for serotonin production) is signaled to release serotonin during and after a meal to suppress appetite. similarly, salivary nuclei are signaled to decrease saliva secretion. hypoglossal and thalamic connections aid in oral-related movements. hypothalamus connections hormonally regulate hunger and the digestive system. substantia innominata connects the thalamus, temporal lobe, and insula. edinger-westphal nucleus reacts to taste stimuli by dilating and constricting the pupils. spinal ganglion are involved in movement. the frontal operculum is speculated to be the memory and association hub for taste. the insula cortex aids in swallowing and gastric motility. other concepts supertasters main article: supertaster a supertaster is a person whose sense of taste is significantly more sensitive than most. the cause of this heightened response is likely, at least in part, due to an increased number of fungiform papillae. studies have shown that supertasters require less fat and sugar in their food to get the same satisfying effects. these people tend to consume more salt than others. this is due to their heightened sense of the taste of bitterness, and the presence of salt drowns out the taste of bitterness. (this also explains why supertasters prefer salted cheddar cheese over non-salted.) aftertaste main article: aftertaste aftertastes arise after food has been swallowed. an aftertaste can differ from the food it follows. medicines and tablets may also have a lingering aftertaste, as they can contain certain artificial flavor compounds, such as aspartame (artificial sweetener). acquired taste an acquired taste often refers to an appreciation for a food or beverage that is unlikely to be enjoyed by a person who has not had substantial exposure to