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12 Delectable Facts About the Science of Taste

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Now that the holiday season is over, you may be cutting back on indulgent meals because of your waistline. But your taste buds are eager for flavor year-round. A lot more than your tongue is involved in the process of tasting food. Taste is not only one of the most pleasurable of all the senses, but a surprisingly complex sense that science is beginning to understand—and manipulate. Here are 12 fascinating facts about your ability to taste. 

1. EVERYONE HAS A DIFFERENT NUMBER OF TASTE BUDS.

We all have several thousand taste buds in our mouths, but the number varies from person to person; between 2000 and 10,000 is the average range. And taste buds are not limited to your tongue; they can be found in the roof and walls of your mouth, throat, and esophagus. As you age, your taste buds become less sensitive, which experts believe may be why foods that you don’t like as a child become palatable to you as an adult. 

2. YOU TASTE WITH YOUR BRAIN.

The moment you bite into a slice of pie, your mouth seems full of flavor. But most of that taste sensation is happening in your brain. More accurately, cranial nerves and taste bud receptors in your mouth send molecules of your food to olfactory nerve endings in the roof of your nose. The molecules bind to these nerve endings, which then signal the olfactory bulb to send smell messages directly to two important cranial nerves, the facial nerve and the glossopharyngeal nerve, which communicate with a part of the brain known as the gustatory cortex.

As taste and nerve messages move further through the brain, they join up with smell messages to give the sensation of flavor, which feels as if it comes from the mouth.

3. YOU CAN'T TASTE WELL IF YOU CAN'T SMELL.

When you smell something through your nostrils, the brain registers these sensations as coming from the nose, while smells perceived through the back of the throat activate parts of the brain associated with signals from the mouth. Since much of taste is odor traveling to olfactory receptors in your brain, it makes sense that you won’t taste much at all if you can’t smell. If you are unable to smell for reasons that include head colds, smoking cigarettes, side effects of medications, or a broken nose, olfactory receptors may either be too damaged, blocked, or inflamed to send their signals on up to your brain. 

4. EATING SWEET FOODS HELPS FORM A MEMORY OF A MEAL.

Eating sweet foods causes the brain to form a memory of a meal, according to a new study in the journal Hippocampus, and researchers believe it can actually help you control eating behavior. Neurons in the dorsal hippocampus, the part of the brain central to episodic memory, are activated when you eat sweets. Episodic memory is that kind that helps you recall what you experienced at a particular time and place. "We think that episodic memory can be used to control eating behavior," said study co-author Marise Parent, of the Neuroscience Institute at Georgia State. "We make decisions like 'I probably won't eat now. I had a big breakfast.' We make decisions based on our memory of what and when we ate."

5. SCIENTISTS CAN TURN TASTES ON AND OFF BY ACTIVATING AND SILENCING CLUSTERS OF BRAIN CELLS.

Dedicated taste receptors in the brain have been found for each of the five basic tastes: sweet, sour, salty, bitter, and umami (savory).  Recently, scientists outlined in the journal Nature how they were able to turn specific tastes “on” or “off” in mice, without introducing food, by stimulating and silencing neurons in the brains. For instance, when they stimulated neurons associated with “bitter,” mice made puckering expressions, and could still taste sweet, and vice versa. 

6. YOU CAN TWEAK YOUR TASTE BUDS.

Most of us have had the unfortunate, mouth-puckering experience of drinking perfectly good orange juice after brushing our teeth only to have it taste more like unsweetened lemon juice. Taste buds, it turns out, are sensitive enough that certain compounds in foods and medicines can alter our ability to perceive one of the five common tastes. The foaming agent sodium lauryl/laureth sulfate in most toothpaste seems to temporarily suppress sweetness receptors. This isn't so unusual. A compound called cynarin in artichokes temporarily blocks your sweet receptors. Then, when you drink water, the cynarin is washed away, making your sweet receptors “wake up” and thus making the water taste sweet. A compound called miraculin, found in the Indian herb Gymnema sylvestre, toys with your sweet receptors in a similar way. 

7. THE SMELL OF HAM CAN MAKE YOUR FOOD "TASTE" SALTIER.

There’s an entire industry that concocts the tastes of the food you buy at the grocery store. Working with phenomena known as phantom aromas or aroma-taste interactions, scientists found that people associate “ham” with salt. So simply adding a subtle “ham-like” scent or subtle flavor to a food can make your brain perceive it as saltier than it actually is. The same concept applies to the scent of vanilla, which people perceive as sweet. 

8. YOUR TASTE BUDS PREFER SAVORY WHEN FLYING.

A study by Cornell University food scientists found that loud, noisy environments, such as when you’re traveling on an airplane, compromise your sense of taste. The study found that people traveling on airplanes had suppressed sweet receptors and enhanced umami receptors. The German airline Lufthansa confirmed that on flights, passengers ordered nearly as much tomato juice as beer. The study opens the door to new questions about how taste is influenced by more than our own internal circuitry, including our interactions with our environments.

9. PICKY EATERS MAY BE "SUPERTASTERS.”

The picky eater may have a new excuse to turn down your homecooked meal: An extreme dislike of eggplant or sensitivity to the slightest hint of onion may mean you are a supertaster—one of 25 percent of people who have extra papillae in your tongue, in essence, a greater number of taste buds, thus receptors. 

10. SOME OF YOUR TASTE PREFERENCES ARE GENETIC.

While your genetics may not explain your love of peanut butter and mayonnaise sandwiches or rocky road ice cream specifically, there may be code written into your DNA that accounts for your preference for sweet foods or your aversion to certain flavors. The first discovery of a genetic underpinning to taste came in 1931, when a chemist named Arthur Fox was working with powdered PTC (phenylthiocarbamide), and some of the compound blew into the air. One colleague found it to have a bitter taste, while Fox did not perceive this. They conducted an experiment among friends and family and found wide variation in how (and whether) people perceived the flavor of the PTC to be bitter or tasteless. Geneticists later discovered that the perception of PTC flavor (similar to naturally occurring compounds) is based in a single gene, TAS2R38, that codes for a taste receptor on the tongue. In a 2005 study, researchers at the Monell Chemical Senses Center found that the version of this gene also predicted a child's preference for sweet foods.

11. IN FACT, YOUR GENES INFLUENCE WHETHER CILANTRO TASTES LIKE AN HERB OR LIKE SOAP.

There may be no flavor more hotly debated or deeply loathed than the humble cilantro herb (also known as coriander). Entire websites such as IHateCilantro.com exist extolling dislike for the herb’s “soapy” or “perfumy” flavor, while those who like it simply think it gives a nice kick to their salsa. Researchers at the consumer genetics firm 23andMe identified two common genetic variants linked to people's “soap” perceptions. A follow-up study in a separate subset of customers confirmed the associations. The most compelling variant can be found within a cluster of olfactory receptor genes, which influence our sense of smell. One of those genes, OR6A2, encodes a receptor that is highly sensitive to aldehyde chemicals, which cilantro contains.

12. SUGAR CRAVINGS HAVE A BIOLOGICAL BASIS.

Your urge for more hot fudge may have little to do with a lack of self-control; scientists believe that our yearning for sweets is a biological preference that may have been designed to ensure our survival. The liking for sweet tastes in our ancient evolution may have ensured the acceptance of sweet-tasting foods, such as breast milk and vitamin-rich fruits. Moreover, recent research suggests that we crave sweets for their pain-reducing properties

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Scientists Accidentally Make Plastic-Eating Bacteria Even More Efficient
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In 2016, Japanese researchers discovered a type of bacteria that eats non-biodegradable plastic. The organism, named Ideonella sakaiensis, can break down a thumbnail-sized flake of polyethylene terephthalate (PET), the type of plastic used for beverage bottles, in just six weeks. Now, The Guardian reports that an international team of scientists has engineered a mutant version of the plastic-munching bacteria that's 20 percent more efficient.

Researchers from the U.S. Department of Energy's National Renewable Energy Laboratory and the University of Portsmouth in the UK didn't originally set out to produce a super-powered version of the bacteria. Rather, they just wanted a better understanding of how it evolved. PET started appearing in landfills only within the last 80 years, which means that I. sakaiensis must have evolved very recently.

The microbe uses an enzyme called PETase to break down the plastic it consumes. The structure of the enzyme is similar to the one used by some bacteria to digest cutin, a natural protective coating that grows on plants. As the scientists write in their study published in the journal Proceedings of the National Academy of Sciences, they hoped to get a clearer picture of how the new mechanism evolved by tweaking the enzyme in the lab.

What they got instead was a mutant enzyme that degrades plastic even faster than the naturally occurring one. The improvement isn't especially dramatic—the enzyme still takes a few days to start the digestion process—but it shows that I. sakaiensis holds even more potential than previously expected.

"What we've learned is that PETase is not yet fully optimized to degrade PET—and now that we've shown this, it's time to apply the tools of protein engineering and evolution to continue to improve it," study coauthor Gregg Beckham said in a press statement.

The planet's plastic problem is only growing worse. According to a study published in 2017, humans have produced a total of 9 billion tons of plastic in less than a century. Of that number, only 9 percent of it is recycled, 12 percent is incinerated, and 79 percent is sent to landfills. By 2050, scientists predict that we'll have created 13 billion tons of plastic waste.

When left alone, PET takes centuries to break down, but the plastic-eating microbes could be the key to ridding it from the environment in a quick and safe way. The researchers believe that PETase could be turned into super-fast enzymes that thrives in extreme temperatures where plastic softens and become easier to break down. They've already filed a patent for the first mutant version of the enzyme.

[h/t The Guardian]

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15 Overlooked Facts about Rosalind Franklin
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Robin Stott, via Flickr // CC BY-SA 2.0

Today is the 60th anniversary of the death of English chemist Rosalind Franklin, a brilliant and dedicated scientist best known for the honor denied her: the 1962 Nobel Prize for discovering the structure of DNA. Here are 15 facts about her.

1. SHE KNEW HER CALLING EARLY, BUT HER FATHER RESISTED EDUCATING A DAUGHTER.

Rosalind Elsie Franklin was born in London in 1920. She was one of five children born into a wealthy Jewish family. She decided she wanted to become a scientist at 15, and passed the admissions exam for Cambridge University. However, her father, Ellis, a merchant banker, objected to women going to college and refused to pay her tuition. Her aunt and mother finally managed to change his mind, and she enrolled at Cambridge's all-female Newnham College in 1938.

2. SHE ATTENDED COLLEGE WITH ANOTHER WOMAN WHO DIDN'T GET FULL CREDIT FOR HER WORK.

Bletchley Park cryptanalyst Joan Clarke was a few years older than Franklin, but they were both at Newnham in the late 1930s. Clarke would go on to be recruited for the war effort, cracking the German Enigma codes. The full scope of Clarke's work is still unknown, due to government secrecy.

3. HER SCHOLASTIC ACHIEVEMENTS WERE DENIED BY HER UNIVERSITY FOR YEARS.

Newnham College, Cambridge
Azeira, Wikimedia Commons // Public Domain

Despite Newnham College having been at Cambridge since 1871, the university refused to accept women as full members until 1948, seven years after Franklin earned the title of a degree in chemistry. Oxford University started granting women's degrees in 1920.

4. HER RESEARCH ON COAL HELPED THE AEROSPACE INDUSTRY.

After graduation, Franklin got a job at the British Coal Utilization Research Association (BCURA), where she researched coal and charcoal, and how it could be used for more than fuel. Her research formed the basis for her 1945 doctoral dissertation; it and several of her later papers on the micro-structures of carbon fibers played a role in the eventual use of carbon composites in air- and spacecraft construction.

5. HER MALE COLLEAGUES WERE HOSTILE AND UNDERMINED HER RESEARCH.

Franklin had a direct nature and was unwilling to be traditionally feminine. One reason she left Cambridge to work on coal was that her doctoral supervisor did not like her and believed women would always be less than men. When she was hired in 1951 at King's College, London, to work on DNA, she clashed with researcher Maurice Wilkins, who had thought she was his assistant, not his equal. Meanwhile, Franklin was under the impression that she'd be completely independent. Their relationship got worse and worse the longer they worked together. Wilkins went so far as to share Franklin's research without telling her with James Watson and Francis Crick—even though they were technically his competitors, funded by Cambridge University. Watson was particularly nasty about Franklin in his 1968 book, The Double Helix, criticizing her appearance and saying she had to be “put in her place.”

6. HOW EVENTS UNFOLDED IN THE DISCOVERY OF DNA'S STRUCTURE IS STILL DEBATED TODAY.

Double helix of DNA
Altayb, iStock

Many books have been written hashing over events, either criticizing Watson and Crick, saying they stole Franklin's research, or defending the duo, saying her research helped them but that Franklin would not ultimately have reached their conclusions on her own. Though Franklin and Watson never became friendly, Crick and his wife welcomed Franklin into their home while she was being treated for ovarian cancer.

7. HER WORK MAY HAVE LED TO HER UNTIMELY DEATH.

Franklin died of cancer in 1958. She was 37. Though genetics likely played a part in her illness, her work with crystal x-ray diffraction, which involved constant exposure to radiation, did not help. She is not the first woman in science to risk her health for her research. Marie Curie died from aplastic anemia, which has been tied to radiation exposure. Many of Curie's personal belongings, including her cookbooks, are too radioactive to handle even today.

8. HAD SHE LIVED LONGER, SHE MAY HAVE QUALIFIED FOR MORE THAN ONE NOBEL PRIZE.


Maurice Wilkins (on left), Francis Crick (third from left), and James Watson (fifth from left) accept their Nobel Prize in 1962.
Keystone, Getty Images

The first, of course, would have been awarded with Watson, Crick, and Wilkins, had they been made to share credit with her. (Pierre Curie had to ask the Nobel Committee to add his wife to the nomination in 1903.) As for the second, chemist Aaron Klug won the prize in 1982, carrying on work he and Franklin had started on viruses in 1953, after she left King's College. Because of the rules at the time of her death about awarding prizes posthumously (and in 1974 all posthumous awards were eliminated, the sole exception being in 2011), Franklin has none.

9. DESPITE BEING DENIED HER PRIZE, SHE'S BEEN HONORED BY MANY ACADEMICS.

In 2004, the Chicago Medical School renamed itself the Rosalind Franklin University of Medicine and Science. She has also had a number of academic programs, auditoriums, and labs named for her. In 2013, Newnham College principal Dame Carol Black helped install a plaque commemorating Franklin at the Eagle Pub in Cambridge. Crick and Watson, who already had a plaque in the pub, drank there often while working on the DNA project, and allegedly boasted about discovering “the secret of life” to other patrons.

10. SHE IS THE SUBJECT OF SEVERAL BIOGRAPHIES.

The first, 1975's Rosalind Franklin and DNA, was written by her friend Anne Sayre, largely as a reaction to Watson's The Double Helix. In 2002, Brenda Maddox published Rosalind Franklin: The Dark Lady of DNA.

11. AN OBJECT IN SPACE IS NAMED AFTER HER.

In 1997, amateur Australian astronomer John Broughton discovered an asteroid, which he named 9241 Rosfranklin.

12. AT LEAST ONE HISTORY RAP BATTLE IS ABOUT HER.

It was produced by seventh graders in Oakland, California (with some help from teacher Tom McFadden). And it is delightful.

13. SHE HAS BEEN IMMORTALIZED ON THE SMALL SCREEN AND THE BIG STAGE.

In 1987, BBC's Horizon series aired The Race for the Double Helix, starring Juliet Stevenson as Franklin. Jeff Goldblum played Watson. In 2011, playwright Anna Ziegler premiered a one-act about Franklin called Photograph 51. It opened on the West End in 2015, starring Nicole Kidman as Franklin.

14. THE 2015 RUN OF PHOTOGRAPH 51 RE-IGNITED THE OLD CONTROVERSY.

While Kidman got much praise from critics for her turn as Franklin in Photograph 51, Maurice Wilkins' friends and former colleagues have taken exception to a scene where Wilkins takes a photograph—the titular Photo 51, which showed evidence of DNA's structure—from Franklin's desk when she isn't there, saying he would never have done something so dishonorable.

15. THE PLAY MAY COME TO THE BIG SCREEN IN THE NEXT FEW YEARS.

In 2016, the West End production's director, Michael Grandage, told The Hollywood Reporter that he hopes to turn the play into a film, with Kidman reprising the role.

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