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"Sour" redirects here. For the Lebanese city, see Tyre, Lebanon . The basic tastes are the commonly recognized types of Taste Sense d by Human s. Humans receive tastes through sensory organs called '' Taste Bud s'' or ''gustatory calyculi'', concentrated on the upper surface of the (described as savoury, meaty, or brothy). Taste and Smell are subsumed under the term '' Flavor ''. The basic tastes are only one component that contributes to the sensation of food in the mouth — other factors include the food's Smell , detected by the Olfactory Epithelium of the nose, its Texture , detected by Mechanoreceptor s, and its temperature, detected by Thermoreceptor s. HISTORY In Western culture, the concept of basic tastes can be traced back at least to Aristotle , who cited " Sweet " and " Bitter ," with "succulent," " Salt ," " Pungent ," "harsh," " Astringent " and "acid" as elaborations of those two basics. The ancient Chinese Five Elements philosophy lists slightly different five basic tastes: bitter, salty, sour, sweet, and spicy. Japanese and Indian cultures each add their own sixth taste to the basic five. For many years, books on the Physiology of human taste contained diagrams of the tongue showing levels of sensitivity to different tastes in different regions. In fact, taste qualities are found in all areas of the tongue, in contrast with the popular view that different tastes map to different areas of the tongue.Huang A. L., et al. 1 Nature, 442. 934 - 938 (2006).2 August 25, 2006. RECENT DISCOVERIES The Receptors for all known basic tastes have been identified. The receptors for sour and salty are Ion Channel s while the receptors for sweet, bitter, and umami belong to the class of G Protein Coupled Receptor s. In November 2005, it was reported that a team of French researchers experimenting on rodents claimed to have evidence for a sixth taste, for fatty substances. It is speculated that humans may also have the same receptors. Fat has occasionally been raised as a possible basic taste since at least the 1800s. FIVE BASIC TASTE Saltiness Saltiness is a taste produced by the presence of Sodium Chloride (and to a lesser degree other Salt s). The ions of salt, especially sodium (Na+), can pass directly through ion channels in the tongue, leading to an Action Potential . Sourness Sourness is the taste that detects Acid ity. The mechanism for detecting sour taste is similar to that which detects salt taste. Hydrogen Ion Channels detect the concentration of Hydronium Ion s (H3O+ ions) that are formed from acids and water. Hydrogen ions are capable of permeating the amiloride-sensitive sodium channels, but this is not the only mechanism involved in detecting the quality of sourness. Hydrogen ions also inhibit the potassium channel, which normally functions to hyperpolarize the cell. Thus, by a combination of direct intake of hydrogen ions (which itself depolarizes the cell) and the inhibition of the hyperpolarizing channel, sourness causes the taste cell to fire in this specific manner. Sweetness See Also: Sweetness Sweetness is produced by the presence of Sugar s, some proteins and a few other substances. Sweetness is often connected to Aldehyde s and Ketone s, which contain a Carbonyl Group . Sweetness is detected by a variety of G Protein Coupled Receptor s coupled to the G Protein Gustducin found on the Taste Bud s. At least two different variants of the "sweetness receptors" need to be activated for the brain to register sweetness. The compounds which the brain senses as sweet are thus compounds that can bind with varying bond strength to two different sweetness receptors. These receptors are T1R2+3 (heterodimer) and T1R3 (homodimer), which are shown to be accountable for all sweet sensing in humans and animals (8). The average human detection threshold for Sucrose is 10 millimoles per litre. For Lactose it is 30 millimoles per litre, and 5-Nitro-2-propoxyaniline 0.002 millimoles per litre. See Also: Miraculin Curculin Bitterness The bitter taste is perceived by many to be unpleasant, sharp, or disagreeable. Evolutionary Biologists have suggested that a distaste for bitter substances may have evolved as a defense mechanism against accidental Poisoning . Common bitter foods and beverages include Coffee , unsweetened Chocolate , Bitter Melon , Beer , uncured Olives , Citrus Peel , many plants in the Brassicaceae family, Dandelion greens and Escarole . Quinine , the anti-malarial Prophylactic , is also known for its bitter taste and is found in Tonic Water . The bitterest substance known is the synthetic chemical Denatonium , discovered in 1958. It is used as an Aversive Agent that is added to toxic substances to prevent accidental ingestion. Research has shown that TAS2Rs (taste receptors, type 2) such as TAS2R16 coupled to the G Protein gustducin are responsible for the human ability to taste bitter substances. They are identified not only by their ability to taste for certain "bitter" ligands, but also by the morphology of the receptor itself (surface bound, monomeric).Lindemann "Receptors and transduction in taste." Nature 2001 Researchers use two synthetic substances, Phenylthiocarbamide (PTC) and 6-n-propylthiouracil (PROP) to study the Genetics of bitter perception. These two substances taste bitter to some people, but are virtually tasteless to others. Among the tasters, some are so-called " Supertaster s" to whom PTC and PROP are extremely bitter. This genetic variation in the ability to taste a substance has been a source of great interest to those who study genetics. In addition, it is of interest to those who study Evolution since PTC-tasting is associated with the ability to taste numerous natural bitter compounds, a large number of which are known to be toxic. Savouriness See Also: umami Savouriness is the name for the taste sensation produced by compounds such as Glutamate are commonly found in Fermented and aged foods. In English, it is sometimes described as "meaty" or "savoury". In Japanese , the term ''umami'' (旨味, うまみ) is used for this taste sensation, whose characters literally mean "delicious flavour." Umami is now the commonly used term by taste scientists. The same taste is referred to as ''xiānwèi'' (鮮味 or 鲜味) in Chinese cooking. Savoury is considered a fundamental taste in Chinese and Japanese cooking, but is not discussed as much in Western Cuisine . Examples of food containing these glutamate (and thus strong in the savoury taste) are Parmesan and Roquefort Cheese as well as Soy Sauce and Fish Sauce . It is also found in significant amounts in various unfermented foods such as Walnut s, Grape s, Broccoli , Tomato es, and Mushroom s, and to a lesser degree in Meat . The glutamate taste sensation is most intense in combination with Sodium . This is one reason why tomatoes exhibit a stronger taste after adding Salt . Sauces with savoury and salty tastes are very popular for cooking, such as tomato sauces and Ketchup for Western cuisines and soy sauce and fish sauce for East Asia n and Southeast Asia n cuisines. Since not every glutamate produces a savoury-like taste sensation, there is continuing investigation into the exact mechanism of how the savoury taste sensation is produced. The additive Monosodium Glutamate (MSG), which was developed as a food additive in 1907 by Kikunae Ikeda , produces a strong savoury taste. Savoury is also provided by the Nucleotide s Disodium 5’-inosine Monophosphate (IMP) and Disodium 5’-guanosine Monophosphate (GMP). These are naturally present in many protein-rich foods. IMP is present in high concentrations in many foods, including dried Skipjack Tuna flakes used to make '' Dashi '', a Japanese broth. GMP is present in high concentration in dried '' Shiitake '' mushrooms, used in much of the Cuisine Of Asia . There is a synergistic effect between MSG, IMP and GMP which together in certain ratios produce a strong umami taste. A subset of savoury taste buds responds specifically to Glutamate in the same way that ''sweet'' ones respond to sugar. Glutamate binds to a variant of G Protein Coupled Glutamate Receptors . 3 Earlier reports had postulated that a Metabotropic Glutamate Receptor (mGluR4) and the NMDA Receptor might play a role in umami perception. MORE SENSATIONS The tongue can also feel other sensations, not generally called tastes '' Per Se '' or included in the five human tastes. These are largely detected by the Somatosensory system. Temperature Temperature is an essential element of human taste experience. Food and drink that — within a given culture — is considered to be properly served hot is often considered distasteful if cold, and ''vice versa''. Coolness Some substances activate cold Trigeminal receptors. One can sense a cool sensation (also known as "fresh" or "minty") from, e.g., Spearmint , Menthol , ethanol or Camphor , which is caused by the food activating the TRP-M8 ion channel on Nerve Cell s that also signal cold. Unlike the actual change in temperature described for sugar substitutes, coolness is only a perceived phenomenon. Spiciness or Hotness See Also: Scoville scale 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 activating a nerve cell called TRP-V1, which is also activated by hot temperatures. The sensation, usually referred to as being "hot" or "spicy", is a notable feature of Mexican , Indian , Szechuan , Korean , Indonesian , central Vietnamese , and Thai Cuisines . The two main plants providing this sensation are Chili Pepper s (those fruits of the '' Capsicum '' plant that contain capsaicin) and Black Pepper . Numbness Chinese cooking includes the idea of 麻 ''má'', the sensation of tingling numbness caused by spices such as Sichuan Pepper . The cuisine of Sichuan province often combines this with Chili Pepper to produce a 麻辣 ''málà'', "numbing-and-hot", flavour.http://www.uni-graz.at/~katzer/engl/Zant_pip.html?noframes] Fat Recent research has revealed a potential taste receptor called the , but probably exists among other Mammal s as well. In experiments, mice with a genetic defect that blocked this receptor didn't show the same urge to consume fatty acids as normal mice, and failed to prepare Gastric Juice s in their Digestive Tracts to digest fat. This discovery may lead to a better understanding of the biochemical reasons behind this behaviour, although more research is still necessary to confirm the relationship of CD36 and the cravings of fat. Kokumi Some Japanese researchers refer to a flavour called ''kokumi'' which has been described variously as continuity, "mouthfulness", mouthfeel and thickness. Kasaaya In Indian tradition, the tastes are referred to as 'Arusuvai' or six tastes {Link without Title} . These tastes are normally referred to as the following: sweet, sour, salty, bitter, hot / spicy and astringent. Some people call the sixth taste as neutral or tasteless. A typical example of a neutral tasting substance is water. Certain others say the astringent or the sixth taste is a mix of varied tastes and is termed Kasaaya, in India. That is more in line with the Japanese approach to umami. Astringency Some foods, such as unripe fruits, contain Tannins or Calcium Oxalate that cause an astringent or rough sensation of the mucous membrane of the mouth or the teeth. Examples include Tea , Rhubarb , Grapes and unripe Persimmon s and Banana s. Less exact terms for the astringent sensation include: "rubbery", "hard", "styptic", "dry", "rough", "harsh" (especially for wine) and "tart" (normally referring to sourness) http://www3.interscience.wiley.com/cgi-bin/abstract/68000103/ABSTRACT?CRETRY=1&SRETRY=0. The Chinese have a term for this: 澀 (''sè''), the Korean have 떫다 (''tteolda''), the Japanese call it 渋い (''shibui''), while Thai have ฝาด (fard), the Malay use ''kelat'', and in Russian there is ''вяжущий (vyazhuschiy)'' or ''тёрпкий (tjorpky)''. Metallic taste All people know this taste (e.g. Cu2+, FeSO4, or blood in mouth), but it is not only taste but olfactory receptors worked in this case (''Guth'' and ''Grosch'', 1990).
REFERENCES (8) Zhao G.Q., et al. Cell, 255-256 (2003)
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