Tip of the Tongue: Humans May Taste at Least 6 Flavors Tip of the Tongue: Humans May Taste at Least 6 Flavors By Adam Hadhazy | December 30, 2011 11:59am ET MORE Scientists disagree about whether humans can detect more than five basic tastes (sweet, sour, bitter, salty and umami). Credit: Rafa Irusta , Shutterstock We cook, therefore we are. Over the millennia, humankind – hardly content to eat plants, animals and fungi raw – has created a smorgasbord of cuisines. Yet for all our sophistication in the kitchen, the scientific understanding of how we taste food could still use some time in the oven. Dating back to ancient Greece and China, the sensation of taste has historically been described as a combination of a handful of distinct perceptions. Western food research, for example, has long been dominated by the four "basic tastes" of sweet, bitter, sour and salty. In recent decades, however, molecular biology and other modern sciences have dashed this tidy paradigm. For example, Western science now recognizes the East's umami (savory) as a basic taste.

But even the age-old concept of basic tastes is starting to crumble. "There is no accepted definition of a basic taste," said Michael Tordoff, a behavioral geneticist at the Monell Chemical Senses Center in Philadelphia. "The rules are changing as we speak." Our ability to sense the five accepted categories comes from receptors on our taste buds. These tiny sensory organs appear mostly on the tongue, the roof of the mouth and in the back of the throat. The sense of touch also plays a key role in experiencing taste, as evidenced by the strong opinions on crunchy versus smooth peanut butter. Smell, too, impacts our tasting abilities. Just ask anyone with a stuffed-up nose picking away at what seems to be a plate of bland food. [ Supertaster vs. Nontaster ] In the mouth itself, though, food scientists continue to discover new receptors and new pathways for gustatory impressions to reach our brain. Here are some taste sensations vying for a place at the table as a sixth basic taste. 1. Calcium The element calcium is critical in our bodies for muscle contraction, cellular communication and bone growth. Being able to sense it in our chow, therefore, would seem like a handy tool for survival.

Mice seem to have it figured out, kind of. Recent research has revealed that the rodents' tongues have two taste receptors for calcium . One of those receptors has been found on the human tongue, though its role in directly tasting calcium is not yet settled, said Tordoff. Calcium clearly has a taste, however, and counterintuitively most mice (and humans) don't like it. People have described it as sort of bitter and chalky – even at very low concentrations. Tordoff thinks our calcium taste might actually exist to avoid consuming too much of it. An over-sensitivity to calcium-rich foods such as spinach could help explain why four out of five Americans don't get enough calcium. "There is a strong relation between people not liking vegetables and calcium," said Tordoff. As for milk and other calcium-loaded dairy, the calcium in it binds to the fat, so we don't taste the mineral all that much, Tordoff noted. 2.

Kokumi That calcium receptor might also have something to do with an unrelated sixth-taste candidate called kokumi , which translates as "mouthfulness" and "heartiness." Kokumi has been promulgated by researchers from the same Japanese food company, Ajinomoto, who helped convince the taste world of the fifth basic taste, umami, a decade ago. Ajinomoto scientists published a paper in early 2010 suggesting that certain compounds, including the amino acid L-histidine, glutathione in yeast extract and protamine in fish sperm, or milt – which, yes, they do eat in Japan, and elsewhere – interact with our tongue's calcium receptors. The result: an enhancement of flavors already in the mouth, or perhaps a certain richness. Braised, aged or slow-cooked foods supposedly contain greater levels of kokumi. If all that sounds a bit vague, it does to Western scientists also. Ajinomoto representatives have visited Tordoff's group "and given us foods they say are high in kokumi – but we have no idea what they're talking about," he said. "Kokumi may be something that the Western palette is not attuned to." 3.

Piquance Spicy-food lovers delight in that burn they feel on their tongues from peppers. Some Asian cultures consider this sensation a basic taste, known in English as piquance (from a French word). Historically, however, food scientists have not classified this undeniable oral sensation as a taste. That's because certain piquant compounds, such as capsaicin from peppers, directly activate our tongue's touch, rather than taste-bud, receptors. The key piquancy receptor is called TRPV1, and it acts as a "molecular thermometer," said John E. Hayes, a professor of food science at Penn State. Normally, nerves with this receptor send a signal of hotness to the brain when exposed to substances around 107.6 degrees Fahrenheit (42 degrees Celsius), the heat pain threshold for humans. Capsaicin fits into this the TRPV1 receptor and lowers the activation temperature to 95 degrees Fahrenheit (35 degrees Celsius) – cooler than body temperature. Hence, "all of a sudden the receptor is sending signals to brain about 'oh, hot!'" said Hayes, though the food itself is not necessarily hot temperature-wise.

These TRPV1 receptors appear all over the body, which is why exposed mucous membranes in the nose or the eyes also feel the burn of pepper spray, for example. 4. Coolness At the opposite end of taste sensation from piquance's peppers is that minty and fresh sensation from peppermint or menthol. The same trick of sensory perception is at work here – activated touch receptors, called TPRM8 in this case, fool the brain into sensing coldness at normal oral temperatures, said Hayes. As touch sensations, both piquance and coolness are transmitted to the brain via the trigeminal nerve, rather than the three classical nerves for taste. "The set of nerves that carry the burn and cooling sensation are different than from taste sensation," said Hayes. [ 10 Fun Brain Facts ] Still, there is an argument that temperature sensation, both in the genuine sense and in the confused-brain phenomenon of piquance and coolness, deserves to be in the pantheon of basic tastes. Interestingly, Germanic people dating back to 1500 had considered heat sensation as a taste, Hayes said, and the modern debate over temperature's status is far from over. 5.

Metallicity Yet another controversial "taste" is our registering of metals, such as gold and silver, in the oral cavity. Some Asian cultures place gold and silver leaf, as it's called, atop curry dishes and candies, while Europeans fancy a bit of these metallic foils on pastries. The silver foil garnish is known as "vark" when used on Indian sweets, as in the picture above. Although usually tasteless, such garnishes are sometimes reported as having a distinctive flavor. Researchers have shown that this sensation might have something to do with electrical conductivity, in effect giving the tongue a little zap. "If you cut a copper penny in half, expose the zinc core and put it on the tongue, you get a whopping metallic taste," said Harry Lawless, a professor emeritus of food science at Cornell University. "It's like a little battery, with a drop of saliva – you get about 550 millivolts." Lab tests have failed to turn up a metallic-taste receptor, Lawless said, and it remains unclear if electrical conductivity or something more is going on for those shiny culinary embellishments. "We're leaving the door open," Lawless said. 6.

Fat The jury is still out on whether our tongues can taste fat , or just feel its creamy texture. Clearly, many of us enjoy fatty foods, from well-marbled steak to pretty much fried anything. "Fat is a tremendous source of calories," said Linda Bartoshuk, a physiological psychologist at the University of Florida "Eating fat is encouraged by our brains to have us survive." Mice can taste fat, research has shown, and it looks like humans can too, according to a 2010 study in the British Journal of Nutrition. The study revealed varying taste thresholds for fatty acids – the long chains that along with glycerol comprise fats, or lipids – in participants. Intriguingly, the subjects with the higher sensitivities to fat ate fewer fatty menu items and were less likely to be overweight than those with low sensitivity. Bartoshuk, who was not involved in the research, noted that fatty acids "tend to taste bitter in the mouth," and she thinks touch fibers in the taste buds sense the creamy thickness of non-broken-down fat globs instead. 7. Carbon Dioxide Yet another strong sixth taste candidate: carbon dioxide (CO2).

When dissolved in liquids, this gas gives soda, beer, champagne and other carbonated beverages their zingy fizz. [ Infographic: All About Champagne ] That familiar tingling was thought to result from bubbles bursting on the tongue, and had therefore been consigned to the touch category. "It's tricky because CO2 was always considered a trigeminal stimulus," said Tordoff. Researchers presented a strong case for dedicated, taste bud-based carbon dioxide sensors in a Science paper in 2009. They found that an enzyme called carbonic anhydrase 4, which appears on sour taste-sensing cells, specifically detects carbon dioxide in mice. Further evidence comes from a drug called acetazolamide, often taken by climbers to avoid altitude sickness. Acetazolamide blocks the activity of carbonic anhydrase 4. Upon reaching the summit and cracking a beer or popping a bottle of bubbly , climbers have reported that the beverages taste boringly flat. Thus, for those celebrating this New Year's with a traditional glass of champagne, take delight in the range of tastes – whether official or not – that our tongues and brains affords us. Editor's Recommendations It is now generally accepted that the human tongue can detect how many basic tastes?

| Poll Everywhere That's an interesting question! Looks like a Poll Everywhere user asked an audience that very same question. You can crowdsource answers, too! We'll walk you through the steps to turn this question into a live poll. After that, you can ask any crowd, anywhere, anytime. Much more fun than asking Google. It is now generally accepted that the human tongue can detect how many basic tastes? Poll responses are kept private 5 9 14 Ask your audience a question with the Poll Everywhere app Step 2 Audience answers in real time using mobile phones, Twitter, or web browsers Step 3 See your response live on the web or in a PowerPoint presentation Still have questions? Is Poll Everywhere free? Yes! Free plans for K12 and Higher Ed educators include 40 responses per question, and the free business plan allows 25 responses per question. Paid plans allow more responses per question, along with premium features like moderation, post-event reporting, and a custom URL for your audience response page. Is this legit? Yup. We invented this live text/web polling bonanza back in 2007.

Now over 60% of the Fortune 500 and 100,000 educators use Poll Everywhere to engage everyone. We process millions of audience responses every month. The Primary Tastes - How Taste Works | HowStuffWorks The Primary Tastes Prev Next Sour? Sweet? When the primary tastes collide, lemonade is just delicious. Until recently, scientists have accepted four basic tastes. You know them well -- sweet, salty, sour and bitter. They are the building blocks of flavor and at the root of other tastes. Each primary taste triggers a particular gustatory receptor (although receptors can, and frequently do, respond to multiple tastes). The basic tastes went unchallenged for years, perhaps because of their familiarity -- name another taste that is as distinctive as one of the four. In the early 1900s, however, a Japanese scientist sought to detect another taste -- that of the savory seaweed common in Japanese cooking. Kikunae Ikeda eventually isolated glutamic acid as a distinct fifth taste -- one with its very own gustatory receptor. Ikeda named this fifth taste umami, a Japanese word meaning delicious, savory taste. You can taste umami in meats and tomatoes.

Up Next Break the Cycle of Negative Thinking Researchers continued to study umami throughout the 20th century. An important breakthrough came in 1985 when scientists trying to mimic the controversial, flavor-enhancing substance MSG failed to replicate the taste with any combination of the basic four. But because Ikeda's study on taste was not translated into English until 2002 and because the taste of glutamic acid is subtle and less common in Western food , umami has only recently entered the taste canon. Now that the gate is open, however, it's unlikely that scientists will ever be so secure in the limits of primary taste. French researchers even identified a potential gustatory receptor for fat . Fat could actually be the sixth taste. The primary tastes gave early humans clues about what food was good to eat and what was harmful. Sweet foods usually had calories . Salty foods had important vitamins and minerals. Sour foods could be healthy, like oranges, or spoiled, like rotten milk. Bitter tastes were often poisonous. The enhanced flavor of processed food could signify nutritional value that isn't actually there, but our preferences have remained. We still crave and respond to our ancestral favorites, even to our detriment.

So if there are at least five primary tastes, what's up with the tongue map? In the next section we'll learn about the biology-book mainstay and why it might be completely wrong. Taste Assimilation Everything tastes better when you're hungry, right? Well, it actually might. In a study done by researchers at the University of Malawi , groups of students who had not eaten in 16 hours could perceive weaker sucrose and salt solutions than those who had eaten only an hour before. In order to discern taste, students who had just eaten needed a sucrose concentration 50 percent higher and a salt concentration double that of those who had not eaten. But our poison-detecting sense never rests: An empty or full stomach had no effect on the perception of bitterness [source: New York Times ].­ The 5 Senses << Go Back Taste Taste, gustatory perception, or gustation[1] is one of the five traditional senses. Taste is the sensation produced when a substance in the mouth reacts chemically with receptors of taste buds.

Taste, along with smell (olfaction) and trigeminal nerve stimulation (which also handles touch for texture, also pain, and temperature), determines flavors, the sensory impressions of food or other substances. Humans perceive taste through sensory organs called taste buds,[2] or gustatory calyculi, concentrated on the top of the tongue.[3] The tongue is covered with thousands of small bumps called papillae, which are easily visible to the naked eye. Within each papilla are hundreds of taste buds, the organ of taste transduction.[4] There are between 2000 and 5000[5] taste buds that are located on the back and front of the tongue. Others are located on the roof, sides and back of the mouth, and in the throat. Each taste bud contains 50 to 100 taste receptor cells. Taste perception fades with age: On average, people lose half their taste receptors by time they turn 20.[4] The sensation of taste can be categorized into five basic tastes: sweetness, sourness, saltiness, bitterness, and umami. Taste buds are able to differentiate among different tastes through detecting interaction with different molecules or ions.

Sweet, umami, and bitter tastes are triggered by the binding of molecules to G protein-coupled receptors on the cell membranes of taste buds. Saltiness and sourness are perceived when alkali metal or hydrogen ions enter taste buds, respectively.[6] As taste senses both harmful and beneficial things, all basic tastes are classified as either aversive or appetitive, depending upon the effect the things they sense have on our bodies.[7] Sweetness helps to identify energy-rich foods, while bitterness serves as a warning sign of poisons.[8] Schematic drawing of a taste bud. The basic tastes contribute only partially to the sensation and flavor of food in the mouth — other factors include smell,[2] detected by the olfactory epithelium of the nose;[9] texture,[10] detected through a variety of mechanoreceptors, muscle nerves, etc.;[11] temperature, detected by thermoreceptors; and "coolness" (such as of menthol) and "hotness" (pungency), through chemesthesis. Basic Tastes For a long period, it was commonly accepted[who?] that there is a finite and small number of "basic tastes" of which all seemingly complex tastes are ultimately composed.

Just as with primary colors, the "basic" quality of those sensations derives chiefly from the nature of human perception, in this case the different sorts of tastes the human tongue can identify. As of the early twentieth century, physiologists and psychologists believed there were four basic tastes: sweetness, sourness, saltiness, bitterness. At that time umami was not proposed as a fifth taste[19] but now a large number of authorities recognize it as the fifth taste.[citation needed] In Asian countries within the sphere of mainly Chinese and Indian cultural influence, pungency (piquancy or hotness) had traditionally been considered a sixth basic taste. Sweetness Sweetness, usually regarded as a pleasurable sensation, is produced by the presence of sugars and a few other substances. Sweetness is often connected to aldehydes and ketones, which contain a carbonyl group. Sweetness is detected by a variety of G protein coupled receptors coupled to the G protein gustducin found on the taste buds. At least two different variants of the "sweetness receptors" must be activated for the brain to register sweetness. Compounds 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 account for all sweet sensing in humans and animals.[20] Taste detection thresholds for sweet substances are rated relative to sucrose, which has an index of 1.[21][22] The average human detection threshold for sucrose is 10 millimoles per liter. For lactose it is 30 millimoles per liter, with a sweetness index of 0.3,[21] and 5-Nitro-2-propoxyaniline 0.002 millimoles per liter. Sourness Sourness is the taste that detects acidity. The sourness of substances is rated relative to dilute hydrochloric acid, which has a sourness index of 1. By comparison, tartaric acid has a sourness index of 0.7, citric acid an index of 0.46, and carbonic acid an index of 0.06.[21][22] Sour taste is detected by a small subset of cells that are distributed across all taste buds in the tongue.

Sour taste cells can be identified by expression of the protein PKD2L1,[23] although this gene is not required for sour responses. There is evidence that the protons that are abundant in sour substances can directly enter the sour taste cells. This transfer of positive charge into the cell can itself trigger an electrical response. It has also been proposed that weak acids such as acetic acid, which are not fully dissociated at physiological pH values, can penetrate taste cells and thereby elicit an electrical response. According to this mechanism, intracellular hydrogen ions inhibit potassium channels, which normally function to hyperpolarize the cell. 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 action potentials and release neurotransmitter. The mechanism by which animals detect sour is still not completely understood. Saltiness Saltiness is a taste produced primarily by the presence of sodium ions. Other ions of the alkali metals group also taste salty, but the further from sodium the less salty the sensation is. The size of lithium and potassium ions most closely resemble those of sodium and thus the saltiness is most similar.

In contrast rubidium and cesium ions are far larger so their salty taste differs accordingly.[citation needed] The saltiness of substances is rated relative to sodium chloride (NaCl), which has an index of 1.[21][22] Potassium, as potassium chloride - KCl, is the principal ingredient in salt substitutes, and has a saltiness index of 0.6.[21][22] Bitterness Bitterness is the most sensitive of the tastes, and many perceive it as unpleasant, sharp, or disagreeable, but it is sometimes desirable and intentionally added via various bittering agents. Common bitter foods and beverages include coffee, unsweetened cocoa, South American mate, bitter gourd, beer (due to hops), bitters, olives, citrus peel, many plants in the Brassicaceae family, dandelion greens, wild chicory, and escarole. Quinine is also known for its bitter taste and is found in tonic water. Bitterness is the most sensitive of the tastes, and many perceive it as unpleasant, sharp, or disagreeable, but it is sometimes desirable and intentionally added via various bittering agents.

Common bitter foods and beverages include coffee, unsweetened cocoa, South American mate, bitter gourd, beer (due to hops), bitters, olives, citrus peel, many plants in the Brassicaceae family, dandelion greens, wild chicory, and escarole. Quinine is also known for its bitter taste and is found in tonic water.] Umami Umami is an appetitive taste[7] and is described as a savory[36][37] or meaty[37][38] taste. It can be tasted in cheese[39] and soy sauce,[40] and while also found in many other fermented and aged foods, this taste is also present in tomatoes, grains, and beans.[39] Monosodium glutamate (MSG), developed as a food additive in 1908 by Kikunae Ikeda,[41] produces a strong umami taste.[40] See TAS1R1 and TAS1R3 pages for a further explanation of the amino-acid taste receptor.

A loanword from Japanese meaning "good flavor" or "good taste",[42] umami is considered fundamental to many Eastern cuisines[43] and was first described in 1908,[44] although it was only recently recognized in the West as a basic taste.[40][45] Sweet, Sour, Salty, Bitter ... and Umami : Krulwich Wonders... : NPR Sweet, Sour, Salty, Bitter ... and Umami Embed Embed Sweet, Sour, Salty, Bitter ... and Umami Sweet, Sour, Salty, Bitter ... and Umami Embed Embed Heard on Morning Edition Robert Krulwich With his invention of veal stock, French chef Auguste Escoffier set cuisine afire. His dishes had a new taste that was neither salty, sour, sweet nor bitter. Hulton-Deutsch Collection/Corbis hide caption toggle caption Hulton-Deutsch Collection/Corbis So here's a question you don't hear every day: How many tastes can a person taste? There's sweet, of course. Then sour. Then salty. And when the Greek philosopher Democritus took up the question several thousand years ago, he added bitter.

So that makes four. Democritus said (not because he did any experiments; being a philosopher, he thought for a living) that when you chew on your food and it crumbles into little bits, those bits eventually break into four basic shapes. When something tastes sweet, he said, it is because the bits are "round and large in their atoms." Salty is isosceles triangle bits on your tongue, Bitter is "spherical, smooth, scalene and small," while sour is "large in its atoms, but rough, angular and not spherical." And that's it, said Democritus. Everything we taste is some combination of those four ingredients. And that made sense to Plato, and made sense to Aristotle, and pretty much ever since even modern scientists have said that's the number: four. When taste buds were discovered in the 19th century, tongue cells under a microscope looked like little keyholes into which bits of food might fit, and the idea persisted that there were four different keyhole shapes. Article continues after sponsorship An illustration of taste buds from Gray's Anatomy of the Human Body.

When taste buds were discovered in the 19th century, tongue cells under a microscope looked like little keyholes into which bits of food might fit, and the idea persisted that there were four different keyhole shapes. hide caption toggle caption So four it is. Four it was. And then, along came Auguste Escoffier. What the Chef Tasted Escoffier was a chef. Not just a chef, in Paris in the late 1800s he was the chef. He had opened the most glamorous, most expensive, most revolutionary restaurant in the city. He had written a cookbook, The Guide Culinaire. And, says science writer Jonah Lehrer (a colleague of mine on NPR/WNYC's Radio Lab), he also created meals that tasted like no combination of salty, sour, sweet and bitter; they tasted new. Escoffier invented veal stock. And should you choose to listen to our broadcast on Morning Edition, you will hear Jonah and me "cooking" (the sounds were snatched from sound effects records, but I think you will drool anyway) what was then considered a spectacularly new sauce that seemed to deepen and enrich the flavor of everything it touched.

"It didn't just taste good," Jonah says. "This was an epiphany. This was the best food you ever tasted in your life." But because it was neither sweet, bitter, sour, salty nor any combination of those four, as far as the scientists were concerned, it wasn't real. People may smack their lips, drool, savor and pay enormous amounts of money to M. Escoffier, but what they were tasting wasn't really there. It was all in their heads. What the Japanese Soup Lover Tasted Meanwhile, halfway across the world, a chemist named Kikunae Ikeda was at the very same time enjoying a bowl of dashi, a classic Japanese soup made from seaweed. He too sensed that he was tasting something beyond category. Dashi has been used by Japanese cooks much the way Escoffier used stock, as a base for all kinds of foods. And it was, thought Ikeda, simply delicious. Soy sauce contains the taste glutamate, but the Japanese call the flavor "umami," which means yummy. iStockPhoto.com hide caption toggle caption iStockPhoto.com But what was it? Being a chemist, Ikeda could find out.

He knew what he was tasting was, as he wrote, "common to asparagus, tomatoes, cheese and meat but… not one of the four well-known tastes." Ikeda went into his lab and found the secret ingredient. He wrote in a journal for the Chemical Society of Tokyo that it was glutamic acid, but he decided to rename it. He called it "umami," which means "delicious" or "yummy" in Japanese. Umami Glutamate is found in most living things, but when they die, when organic matter breaks down, the glutamate molecule breaks apart. This can happen on a stove when you cook meat, over time when you age a parmesan cheese, by fermentation as in soy sauce or under the sun as a tomato ripens. When glutamate becomes L-glutamate, that's when things get "delicious." L-glutamate, said Ikeda, is a fifth taste. When Escoffier created veal stock, he was concentrating umami. When Japanese made their dashi, they were doing the same thing. When you bite into an anchovy, they are "like glutamate speedballs. They are pure umami," Jonah writes. "Aristotle was wrong.

Plato was wrong. We have five tastes, not four. But when Ikeda's findings were published," Jonah says, "nobody believes him." So Who Was Right? It turns out, almost 100 years after Escoffier wrote his cookbook and Ikeda wrote his article, a new generation of scientists took a closer look at the human tongue and discovered, just as those two had insisted, that yes, there is a fifth taste. Humans do have receptors for L-glutamate and when something is really, really yummy in a non-sweet, sour, bitter or salty way, that's what you're tasting. In 2002, this became the new view. It's in the textbooks now and scientists decided to call this "new" taste, in Ikeda's honor, "umami." If you want to get an umami headache, add some monosodium glutamate to your next bowl of noodles. The Moral In his new book, Proust Was a Neuroscientist, Jonah tells eight stories that share a common theme.

In each case, (he chooses Marcel Proust, Walt Whitman, George Elliot, Paul Cezanne, Igor Stravinsky, Gertrude Stein, Virginia Wolf and, yes Auguste Escoffier) an artist is busy about his/her work and happens to observe something or sense something about the real world that scientists have not yet noticed, or that scientists say is not true. But because artists are so good at describing what it's like to experience the world, so intent on delivering the truth of what it feels like to be alive, so intuitive, in each of these eight cases, the artists learn something that the scientists don't discover until years later. Art, Jonah reminds us, describes the same world that science does; art just does it by a different route. And sometimes, more often than you would suppose, the artists get there first.

Excerpt: 'Proust Was a Neuroscientist' The Tongue Map: Tasteless Myth Debunked The Tongue Map: Tasteless Myth Debunked By Christopher Wanjek | August 29, 2006 04:19am ET MORE The notion that the tongue is mapped into four areas—sweet, sour, salty and bitter—is wrong. There are five basic tastes identified so far, and the entire tongue can sense all of these tastes more or less equally. As reported in the journal Nature this month, scientists have identified a protein that detects sour taste on the tongue. This is a rather important protein, for it enables us and other mammals to recognize spoiled or unripe food. The finding has been hailed as a minor breakthrough in identifying taste mechanisms, involving years of research with genetically engineered mice. This may sound straightforward but, remarkably, more is known about vision and hearing , far more complicated senses, than taste. Maps like this have been around for ages. But they are wrong. LiveScience Bad Graphic. Image: stock.xchange Only in recent years have taste receptors been identified.

One of the first breakthroughs in taste research came in 1974 with the realization that the tongue map was essentially a century-old misunderstanding that no one challenged. You might know the map: The taste buds for "sweet" are on the tip of the tongue; the "salt" taste buds are on either side of the front of the tongue; "sour" taste buds are behind this; and "bitter" taste buds are way in the back. Wineglasses are said to cater to this arrangement. The tongue map is easy enough to prove wrong at home. Place salt on the tip of your tongue. You'll taste salt. For reasons unknown, scientists never bothered to dispute this inconvenient truth. The map has frustrated many a grade-schooler, including me, who couldn't get the experiment right in science class. I failed for insisting I could taste sugar in the back of my tongue. In fact, there's more to taste than sweet, sour, salty and bitter. Most scientists agree that there's a fifth distinct taste, called umami, identified by a Japanese scientist named Kikunae Ikeda in the early 1900s (and ignored by the West for most of the twentieth century).

This is the taste of glutamate. It is common in Japanese foods, particularly kombu, a type of sea vegetable similar to kelp, and in bacon and monosodium glutamate (MSG), which Ikeda isolated and patented. There's considerable debate about the existence of a sixth taste receptor for fat, too. The tongue map dates back to research by a German scientist named D.P. Hanig, published in 1901. Not familiar with Japanese cuisine, Hanig set out to measure the relative sensitivity on the tongue for the four known basic tastes. Based on the subjective whims of his volunteers, he concluded that sensitivity to the four tastes varied around the tongue, with sweet sensations peaking in the tip, etc. That's all. Bad Medicine The Five Senses - Taste The Five Senses - TASTE - Schematic drawing of a taste bud. TASTE (or, the more formal term, gustation; adjectival form: "gustatory") is one of the traditional five senses. It refers to the capability to detect the taste of substances such as food, certain minerals, and poisons, etc.

The sense of taste is often confused with the "sense" of flavor, which is a combination of taste and smell perception. Flavor depends on odor, texture, and temperature as well as on taste. Humans receive tastes through sensory organs called taste buds, or gustatory calyculi, concentrated on the upper surface of the tongue. There are five basic tastes: sweet, bitter, sour, salty and umami. Other tastes such as calcium[6][7] and free fatty acids[8] may be other basic tastes but have yet to receive widespread acceptance. Taste, gustatory perception, or gustation[1] is one of the five traditional senses. Taste is the sensation produced when a substance in the mouth reacts chemically with receptors of taste buds. Taste, along with smell (olfaction) and trigeminal nerve stimulation (which also handles touch for texture, also pain, and temperature), determines flavors, the sensory impressions of food or other substances. Humans perceive taste through sensory organs called taste buds,[2] or gustatory calyculi, concentrated on the top of the tongue.[3] The tongue is covered with thousands of small bumps called papillae, which are easily visible to the naked eye.

Within each papilla are hundreds of taste buds, the organ of taste transduction.[4] There are between 2000 and 5000[5] taste buds that are located on the back and front of the tongue. Others are located on the roof, sides and back of the mouth, and in the throat. Each taste bud contains 50 to 100 taste receptor cells. Taste perception fades with age: On average, people lose half their taste receptors by time they turn 20.[4] The sensation of taste can be categorized into five basic tastes: sweetness, sourness, saltiness, bitterness, and umami. Taste buds are able to differentiate among different tastes through detecting interaction with different molecules or ions. Sweet, umami, and bitter tastes are triggered by the binding of molecules to G protein-coupled receptors on the cell membranes of taste buds.

Saltiness and sourness are perceived when alkali metal or hydrogen ions enter taste buds, respectively.[6] As taste senses both harmful and beneficial things, all basic tastes are classified as either aversive or appetitive, depending upon the effect the things they sense have on our bodies.[7] Sweetness helps to identify energy-rich foods, while bitterness serves as a warning sign of poisons.[8] The basic tastes contribute only partially to the sensation and flavor of food in the mouth - other factorsinclude smell,[2] detected by the olfactory epithelium of the nose;[9] texture,[10] detected through a variety of mechanoreceptors, muscle nerves, etc.;[11] temperature, detected by thermoreceptors; and "coolness" (such as of menthol) and "hotness" (pungency), through chemesthesis. - Basic Tastes - For a long period, it was commonly accepted that there is a finite and small number of "basic tastes" of which all seemingly complex tastes are ultimately composed. Just as with primary colors, the "basic" quality of those sensations derives chiefly from the nature of human perception, in this case the different sorts of tastes the human tongue can identify.

As of the early twentieth century, physiologists and psychologists believed there were four basic tastes: sweetness , sourness , saltiness , bitterness . At that time umami was not proposed as a fifth taste[19] but now a large number of authorities recognize it as the fifth taste.[citation needed] In Asian countries within the sphere of mainly Chinese and Indian cultural influence, pungency (piquancy or hotness) had traditionally been considered a sixth basic taste. Sweetness Sweetness, usually regarded as a pleasurable sensation, is produced by the presence of sugars and a few other substances. Sweetness is often connected to aldehydes and ketones, which contain a carbonyl group. Sweetness is detected by a variety of G protein coupled receptors coupled to the G protein gustducin found on the taste buds. At least two different variants of the "sweetness receptors" must be activated for the brain to register sweetness. Compounds 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 account for all sweet sensing in humans and animals.[20] Taste detection thresholds for sweet substances are rated relative to sucrose, which has an index of 1.[21][22] The average human detection threshold for sucrose is 10 millimoles per liter. For lactose it is 30 millimoles per liter, with a sweetness index of 0.3,[21] and 5-Nitro-2-propoxyaniline 0.002 millimoles per liter. Sourness Sourness is the taste that detects acidity. The sourness of substances is rated relative to dilute hydrochloric acid, which has a sourness index of 1. By comparison, tartaric acid has a sourness index of 0.7, citric acid an index of 0.46, and carbonic acid an index of 0.06.[21][22] Sour taste is detected by a small subset of cells that are distributed across all taste buds in the tongue.

Sour taste cells can be identified by expression of the protein PKD2L1,[23] although this gene is not required for sour responses. There is evidence that the protons that are abundant in sour substances can directly enter the sour taste cells. This transfer of positive charge into the cell can itself trigger an electrical response. It has also been proposed that weak acids such as acetic acid, which are not fully dissociated at physiological pH values, can penetrate taste cells and thereby elicit an electrical response. According to this mechanism, intracellular hydrogen ions inhibit potassium channels, which normally function to hyperpolarize the cell. 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 action potentials and release neurotransmitter. The mechanism by which animals detect sour is still not completely understood. Saltiness Saltiness is a taste produced primarily by the presence of sodium ions. Other ions of the alkali metals group also taste salty, but the further from sodium the less salty the sensation is. The size of lithium and potassium ions most closely resemble those of sodium and thus the saltiness is most similar.

In contrast rubidium and cesium ions are far larger so their salty taste differs accordingly.[citation needed] The saltiness of substances is rated relative to sodium chloride (NaCl), which has an index of 1.[21][22] Potassium, as potassium chloride - KCl, is the principal ingredient in salt substitutes, and has a saltiness index of 0.6.[21][22] Bitterness Bitterness is the most sensitive of the tastes, and many perceive it as unpleasant, sharp, or disagreeable, but it is sometimes desirable and intentionally added via various bittering agents. Common bitter foods and beverages include coffee, unsweetened cocoa, South American mate, bitter gourd, beer (due to hops), bitters, olives, citrus peel, many plants in the Brassicaceae family, dandelion greens, wild chicory, and escarole. Quinine is also known for its bitter taste and is found in tonic water. Bitterness is of interest to those who study evolution, as well as various health researchers[21][26] since a large number of natural bitter compounds are known to be toxic.

The ability to detect bitter-tasting, toxic compounds at low thresholds is considered to provide an important protective function.[21][26][27] Plant leaves often contain toxic compounds, yet even amongst leaf-eating primates, there is a tendency to prefer immature leaves, which tend to be higher in protein and lower in fiber and poisons than mature leaves.[28] Amongst humans, various food processing techniques are used worldwide to detoxify otherwise inedible foods and make them palatable.[29] Umami Umami is an appetitive taste[7] and is described as a savory[36][37] or meaty[37][38] taste. It can be tasted in cheese[39] and soy sauce,[40] and while also found in many other fermented and aged foods, this taste is also present in tomatoes, grains, and beans.[39] Monosodium glutamate (MSG), developed as a food additive in 1908 by Kikunae Ikeda,[41] produces a strong umami taste.[40] See TAS1R1 and TAS1R3 pages for a further explanation of the amino-acid taste receptor.

A loanword from Japanese meaning "good flavor" or "good taste",[42] umami is considered fundamental to many Eastern cuisines[43] and was first described in 1908,[44] although it was only recently recognized in the West as a basic taste.[40][45] References

Question: It is now generally accepted that the human tongue can detect how many basic tastes?
Answer: 5