Job 6:6 (King James Bible)
The tongue is a lie.
Back when I went to school there were four tastes: bitter, salty, sour and sweet. And the taste buds were distributed around the tongue, with sweet at the front, bitter at the back, and salty and sweet along the sides.
It was a lie.
In 1901 a scientist by the name of D.P. Hanig published a study of how people taste. He relied on volunteers, and asked them where on their tongues they thought they tasted various flavors. On the basis of this deeply subjective research, he produced a "map" of flavor sensitivity. Mind you, Hanig never said these were the only places where you could taste various flavors, but that kind of nuance got lost. In popular culture, the tongue map and the four tastes were THE TRUTH.
It wasn't until the 1970s that scientists in Europe and the US became aware of research published in 1908 by the Japanese chemist Kikunae Ikeda that focused on a different flavor which he called "umami," from the words "umai" (delicious) and "mi" (taste). It's been referred to as "savory," and is usually associated with things like meat, mushrooms, miso, and monosodium glutamate.
For many years there was a pronounced distaste (pun intended) toward the idea of a fifth flavor. Even the transcendant Alton Brown was dubious:
'Why do we need another word for it? ... Maybe I've just been exposed to too much marketing in my time. But as far as I'm concerned, umami, you're all smoke and mirrors.' ("Pantry Raid XII: Turing Japanese." Transcript: http://www.goodeatsfanpage.com/season13/miso_soup/turning_jap_tran.htm)
In 2002 it was proven that there are umami taste receptors. And apparently Mr. Brown now (as of 2016) has a signature hamburger available from the Umami Burger chain (see: https://www.umamiburger.com/blog/umami-burger-presents-the-alton-burger-by-alton-brown/). However reluctantly, Alton's on board the umami express.
So now we're up to five flavors. Is that it?
Maybe not. There are at least two additional tastes cresting the horizon: carbonation and fat.
A confession: I LOVE carbonation. Seltzer is my passion. Club soda is my joy. But how can that be? I mean it's just water with bubbles, right? How can it taste good?
It's been known for some time that mosquitoes are attracted to carbon dioxide. And in 2012 a study published in Nature showed that fruit flies are attracted to the taste of carbon dioxide. So the idea that critters might be able to taste carbon dioxide isn't completely far-fetched.
Now it's been proven.
In 2009 Scientific American stated it unequivocally:
"... scientists have discovered that carbonation actually has a flavor." (Scientific American, October 16, 2009. Carbonation Has a Taste. Online: http://www.scientificamerican.com/podcast/episode/carbonation-has-a-taste-09-10-16/)So do we have taste buds that respond to carbonation? Not exactly. It turns out that our sour receptors do double duty:
"Jayaram Chandrashekar of the University of California, San Diego, Charles S. Zuker, formerly of U.C.S.D. and now at Columbia, and colleagues used mice in their studies, implanting electrodes in a nerve leading from taste receptor cells in the tongue. When the tongue was exposed to club soda or even just to gaseous CO2, there was a measurable response in the nerve.No, carbonation doesn't taste sour. Exactly what's going on is still being debated. But yes, carbonation has a flavor. We just don't have a word for it.
"This suggested that taste receptors were responsible. But there are receptors for five tastes: sweet, sour, salty, bitter and umami (sometimes termed savory). They repeated the experiment using mice that had been genetically engineered without one type of receptor. Those without sour receptors showed no response to the carbonation, indicating that those receptors were responsible." (Fountain, Henry. 2009. How Tongues Taste the Carbonation in a Fizzy Beverage. Online: http://www.nytimes.com/2009/10/20/science/20obfizz.html?_r=1)
And fat has a flavor, too:
"In 2010 ... researchers at Deakin University in Australia found that people were able to detect the taste of fatty acids. [In 2012] researchers at the Center for Human Nutrition at Washington University School of Medicine in St. Louis said they had discovered that some people may be more sensitive to the presence of fat in foods than others." (Wan, Julie. 2012. Fat might be the sixth basic taste. Online: https://www.washingtonpost.com/national/health-science/fat-might-be-the-sixth-basic-taste/2012/06/04/gJQAt218DV_story.html)So what does fat taste like?
"The taste of fat, which researchers call "oleogustus" (a combination of the Latin terms for oil and taste), is a distinct flavor and, as a new study in the journal Chemical Senses reports, quite unpleasant." (Kraft, Ann. 2015. Scientists discover the taste of fat, and it's not what you think. Online: http://www.cbsnews.com/news/scientists-discover-the-taste-of-fat-and-its-disgusting/)Apparently it's "bitter and unpalatable." Which may explain why I've never seen much point in unsalted butter.
So, here we are. From four flavors (bitter, salty, sour and sweet) to five (umami) and now seven (carbonation and fat). Is that it?
Probably not:
"molecular biologists have theorized that humans may have as many as 20 distinct receptors for such tastes as calcium ... starch and even water." (Wan, Julie. 2012. Fat might be the sixth basic taste. Online: https://www.washingtonpost.com/national/health-science/fat-might-be-the-sixth-basic-taste/2012/06/04/gJQAt218DV_story.html)So what does all this mean?
Well, for a start, it may help us find better ways to deal with obesity (it might explain why some people consume more fat than others -- it literally tastes good to them). For another, it helps us expand our knowledge of how our bodies function.
And it also helps us in other, less obvious ways. We don't really have a word for "taste of carbonation." Until quite recently, nobody thought we needed one. We don't have words for the taste of fat, or calcium, or metal, or any of the various things that biologists and chemists now suspect are part of what we call "taste."
But we do know that for literally thousands of years people have been desperate to find new tastes, new flavors. The Romans traded with India for pepper. The Dutch and the English fought wars over control of mace and nutmeg. We spend billions of dollars every year coming up with new "flavor additives."
Taste is about more than biochemistry. Taste is something very fundamental to being human. The more we understand taste, the more we understand ourselves.
References
American Mosquito Control Association. 2014. Traps. Online: http://www.mosquito.org/trapsBrown, Alton. Pantry Raid XII: Turning Japanese. First broadcast November 9, 2009. Transcript online: http://www.goodeatsfanpage.com/season13/miso_soup/turning_jap_tran.htm
Does Carbonation Have Flavor? 2012. Online: http://www.livescience.com/32255-does-carbonation-have-flavor.html
Fountain, Henry. 2009. How Tongues Taste the Carbonation in a Fizzy Beverage. Online: http://www.nytimes.com/2009/10/20/science/20obfizz.html?_r=1
Kraft, Ann. 2015. Scientists discover the taste of fat, and it's not what you think. Online: http://www.cbsnews.com/news/scientists-discover-the-taste-of-fat-and-its-disgusting/
McLafferty, Clair. 2014. Why Does Carbonation Make Drinks Taste Good? Online: http://mentalfloss.com/article/56540/why-does-carbonation-make-drinks-taste-good
Midura, Margaretta. 2012. On the Road to Sweetness: A Clear-Cut Destination? Online: http://www.yalescientific.org/2012/11/on-the-road-to-sweetness-a-clear-cut-destination/
O'Callaghan, Jonathan. 2014. The tongue taste map is WRONG: Flavours are actually perceived by neurons in the brain, scientists reveal. Online:
http://www.dailymail.co.uk/sciencetech/article-2828561/The-tongue-taste-map-WRONG-Flavours-actually-perceived-neurons-brain-scientists-reveal.html
Wan, Julie. 2012. Fat might be the sixth basic taste. Online: https://www.washingtonpost.com/national/health-science/fat-might-be-the-sixth-basic-taste/2012/06/04/gJQAt218DV_story.html
Wanjek, Christopher. 2006. The Tongue Map: Tasteless Myth Debunked. Online: http://www.livescience.com/7113-tongue-map-tasteless-myth-debunked.html
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