Posts Tagged ‘food science’

Whether this spread looks appetizing or disgusting to you make have a lot to do with your genes. Image Credit: dboy, Flickr

Why do some people love broccoli, kale and black coffee, while others hold their noses when faced with these bitter-tasting foods? New research published in the journal Chemical Senses this month may help get at the answer.

Our evolutionary history plays a huge role in which flavors we like and which we avoid. Find it impossible to resist that office birthday cake, even though you know you shouldn’t indulge? The excellent cookbook/food science guide Cooking for Geeksinforms me that we probably love fats, sweets and sugars because back when we were hunting and gathering, the foods they were found in (I’m thinking things like ripe wild strawberries and woolly mammoth meat), were tough to get and also high in energy.

Because of these nutritional advantages, fewer of those who had no affinity survived to pass on their genes. However, in the modern landscape of Big Gulps and Applebee’s restaurants, our evolved love of fats, sweets and sugars now works agasint us, and the result is the obesity epidemic.

Almost everybody likes cake and candy bars. But this isn’t true for bitter foods (although many people do seem to acquire a taste for them as they grow up). According to the new paper, we have 25 “bitter” taste receptors, each with its own gene. But all of them aren’t expressed in all of us: which of them are turned on varies wildly from person to person, much more so than for other taste receptors like those for sweet or salty flavors. The paper suggests that this may be due to “local adaptation to the avoidance of plant toxins;” in other words, if your hunting-and-gathering territory included a lot of bitter plants which were also poisonous, the genes of your ancestors would reflect a distaste for the flavor.

The study tested how which versions of the “bitterness genes” a group of 96 subjects had related to their sensitivity to bitter flavors. The participants were given a genetic analysis, and also a taste trial, in which they sampled espresso, scotch whiskey, and unsweetened grapefruit juice and were asked to rank how strongly they liked or disliked the flavor. They found a strong relationship between genes and affinity for bitter flavors: participants who had one version of a certain gene, for example, ranked grapefruit juice as tasting twice as bitter as participants with a different version.

Each of the 25 “bitterness genes” seem to control our liking for different foods. “This study moves us beyond the one-size-fits-all approach,” said lead researcher John Hayes in a press release. “It turns out that different bitter foods act through different receptors, and people can be high or low responders for one but not another. Thus, you may despise grapefruit but have no problem with black coffee.”

Hayes explains that bitter and sweet tastes work in opposition in the brain — so if you perceive a food as tasting more bitter, then it also tastes less sweet to you. “This means not all foods taste the same to all people,” said Hayes. Perhaps this provides insight into why some people are picky eaters and others aren’t.

These genetically-determined taste preferences appear to have real affects in our diets. According to Hayes, people who are more sensitive to bitter tastes eat 25% fewer vegetables, which could put them at greater risk for certain diseases like colon cancer. The study also found that having the “less sensitive” version (called K172) of one of these genes appears to be a risk factor for drinking too much alcohol (alcohol, if you think about it, has a distinctly bitter taste).

If subsequent research backs up these findings, it seems that our tastes may be more influenced by our genes than we thought. If you have a lifelong loathing of spinach and dark chocolate, your picky tastes might be due to a super-sensitivity to bitter flavors. Go ahead and blame your genes if you want, but this research doesn’t give you a pass: veggies are still good for you.



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Case 4.  This was a normal term infant born to a Jewish mother of Iraqi origin. Before delivery, the amniotic fluid was reported to be “yellow and foul smelling”. The baby had a yellowish skin discolouration similar to mecomium staining, and a peculiar odor. Blood cultures from the infant and amniotic fluid cultures were obtained, and antibiotics were administered. On re-examination, the peculiar odour was judged to be identical to that of curry.

This is an excerpt from a report that appeared in The European Journal of Pediatrics in 1985 called “Peculiar odors in newborns and maternal prenatal ingestion of spicy food.” It details four case studies.  In each one, an infant was born, and after doctors and parents had joyfully ascertained that it had two eyes and all the necessary appendages, something else became apparent… the baby smelled a little funky.

Two of the odiferous infants smelled of cumin, one of curry, and one of something called fenugreek (a flowering plant that is a common ingredient in many curries and an herbal remedy for a variety of health conditions). The doctors were concerned because a smelly baby can be a bad sign: strange odors can indicate dangerous conditions such as Maple Syrup Disease, a genetic disorder that causes a buildup of certain amino acids (and the eponymous odor) which can be fatal if untreated.

As it turns out, the stinky newborns weren’t sick: the source of their mysterious odors was pungent, spicy foods their mothers had enjoyed just prior to delivery.  According to the report, “The spices were absorbed from the maternal gastrointestinal tract and transferred to the amniotic fluid, where they were swallowed by the fetus.” It seems that babies can experience mom’s dinner choices directly, and if they don’t like curry, well, that’s just too bad.

Subsequent studies have shown the significance of the mother’s diet on the baby’s environment. In a 1995 study, a group of pregnant women downed garlic pills, then had some smell-testers compare the odor of those women’s amniotic fluid to that of a control group. The testers had no trouble detecting which mothers were garlic-eaters.

And it seems that what the mother eats during pregnancy can actually shape the baby’s future taste preferences. A 2000 paper from the journal Chemical Senses shows that infants whose mothers who ate anise during pregnancy exhibited a preference for the flavor (which has a strong licorice flavor and is not universally liked) after birth. It seems that our tastes start being shaped in the womb (perhaps explaining why we tend to be partial to the foods of our homelands).

However, the strong influence of our mothers’ tastes isn’t always a good thing.

A 2007 study from the British Journal of Medicine showed that pregnant rats fed a “junk food” diet (lots of fats, sugars, and salts) gave birth to babies who showed a preference for a junk food diet throughout life, and as a result, often grew obese. This is especially frightening considering that pregnancy cravings often demand things like ice cream and greasy Chinese takeout.

All in all, mom’s diet seems to affect baby in some intriguing (and amusing) ways. One thing seems certain: if you’re a pregnant woman nearing your due date, you might want to resist those pickle cravings, lest your offspring emerge smelling like a kosher dill.

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For many, behind a tasty glass of wine lurks a blazing headache. Credit: gfpeck, Flickr

Red wine is a fickle friend. It beckons with glistening ruby fingers, luring us into its swirling depths with a siren song of black cherry, currant, and the mysterious soil and mineral tastes of terroir, the taste of the land the grapes grew in. We’re entranced: we sniff, we swirl, we sip, but — unfortunately for our heads — most of us don’t spit.

The resulting red wine headache is a widespread affliction that can strike after as little as one glass. It’s often accompanied by nausea and flushed skin. But this doesn’t happen with white wine, and the majority of us suffer no ill effects from a glass of pinot noir or cabernet sauvignon (unless we knock back too many glasses).

So what’s the deal with the red wine headache? To find out, I turned to Chris Gerling, an oenologist (wine scientist) at Cornell University in Ithaca, New York.

Sulfites are often blamed, says Gerling. Sulfites (or SO2) are a natural component of wine, but they’re also a common preservative, usually added to wine at several stages during its production to prevent bacteria and oxidation. Without sulfites, we couldn’t have wine: grape juice would turn into vinegar. Some people are allergic to sulfites, and it can cause problems for asthmatics too. However, red wine isn’t alone in its sulfite content: in fact, sweet white wines often contain more. And, Gerling points out, “there is no documented danger to the rest of the population, including headaches, at the parts per million levels at which SO2 is found in wine.”

Gerling says that the other main suspect behind the red wine headache is biogenic amines, compounds which are produced by living things and contain nitrogen. They include compounds like histamine and tyrosine, which can have adverse effects if they’re consumed (histamine has been linked to allergies, for example). But once again, Gerling explains, “the concentrations usually thought to cause trouble are much higher than those found in wine.”

Another big hole in the case against sulfites and amines is that both occur in many other foods. Dried fruits like apricots are loaded with sulfites, Gerling says, and amines are present in foods like fish and cheese. Tannins, which are sometimes blamed for red wine headaches, are also found in chocolate and tea. Wine headache sufferers don’t seem to have any more trouble with these food than the general population.

The cause of the phenomenon remains mysterious. “One comparison I often draw is to MSG,” says Gerling. “People are convinced that MSG is the cause of ‘Chinese Food Syndrome,’ but there have been all sorts of studies done where they try to make people react to it and no one ever does. They sprinkle MSG in Italian food and Mexican food and have groups try the food with and without, and people either react to everything (with or without MSG) or they react to nothing. No one ever eats spaghetti with and without MSG and reports feeling ill after only the MSG-laced pasta. Reports of the phenomenon are so widespread, however, that something must be going on.”

One possibility, Gerling says, is that something in the wine is reacting with these compounds, and the headache is the result of this interaction. Alcohol, for example, could perhaps increase the effects of a low dose of sulfites.  Or we could have the wrong suspects: some other chemical compound, or maybe a strain of yeast or bacteria present in red wine, could be to blame.

Unfortunately, without a known cause of the red wine headache, there’s also no proven cure. If you’re one of the unlucky group who suffers from this dreaded curse, your only trustworthy options are sticking to white wine, or (shudder) giving up the libation entirely. I recommend the former.

For more science, check out Scienceline.org, a product of New York University’s Science, Health and Environmental Reporting Program.

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Science you didn’t know you were doing

Image credit: pasukara76 (out of town), Flickr

In a time-lapse video, it looks like a monster coming alive.  For a moment, it sits there innocuously.  Then it pulsates.  Ripples move across its surface.  It begins to bulge outwards, bursting with weird boils.  In mere seconds, it triples in volume, its color darkens ominously, and its surface hardens into an alien topography of peaks and craters.  Then, the kitchen timer dings.  Your cookie is ready.

What happened inside that oven?

Don’t let the sugar and spice deceive you, for the baker is a mad scientist.  In an act of aproned alchemy, she uses her oven to transform one substance into another.  As her sugary creation heats up, the chemical compounds in the dough undergo a series of reactions that change them into different ones.

When the dough reaches 92° Fahrenheit, the butter melts, causing the dough to start spreading out.  As it melts, it releases trapped water, and as the cookie gets hotter, the water expands into steam.  It pushes against the dough from the inside, trying to escape through the cookie walls like Ridley Scott’s chestbursting alien.

When the temperature reaches 136°, it’s too hot for any salmonella that may have been squirming around in the eggs. They die off.  You’ll live to test your fate with the raw dough from your next batch.


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Check out this video profile by me and fellow science writer Ritchie King.  We talked to Dave Breeden, who makes wine in upstate New York at Sheldrake Point winery.  Dave’s quite a character, and he has interesting views on whether winemaking is an art or a science.

Dave Breeden discusses the art and science of winemaking from Scienceline on Vimeo.

If you liked what you saw, you may also want to read my profile of Dave.  He’s quirky and interesting, and he also gave me wine while I interviewed him!

The bottle as beaker

by Stephanie Warren

Dave Breeden pops a ripe cabernet sauvignon grape into his mouth. A look of complete absorption fills his face as he chews. “It’s sweet,” he says. “The seeds are crunchy and ripe. There’s nothing green, no bell pepper flavors.” He looks up from the vines, pleased. “These are ready to go.” On this windblown, brightly sunny October day, it’s time to harvest the grapes. Then they’re off to the crusher-destemmer, the fermenter, the barrel, the bottle, and at long last, the glass. Breeden will watch over them through each step of the process, sniffing, swirling, sipping and spitting what starts out as a muddle of sugars, acids, and other chemical compounds and eventually becomes that magical beverage humans have revered for nearly seven thousand years: wine.

Breeden, 46, is the head vintner at Sheldrake Point Winery in the Finger Lakes area of New York state. He is an endearing mix of bohemian and geek: tall and lanky, he sports glasses and a long graying ponytail, a navy button-up and several silver rings. The rings emphasize his exceptionally long fingers, which he uses to punctuate his every passionate sentence. They fly around him in a blur: now stabbing the air as he denigrates the overripe, jammy flavors of California cabernet sauvignons, now twisted tightly together as talks with a sort of sheepish pride about Sheldrake’s numerous awards.

…read more.

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Test Tube Kitchen is a place for cooks who want to learn more.  If you’ve ever wondered things like:

  • Why does all baking seem to take place at 350°?
  • Why exactly am I supposed to let meat rest after cooking?
  • Is there a foolproof way to make sure my pie crust is flaky?

Then you’ve come to the right place.  At Test Tube Kitchen, I’ll put cooking questions to the test.  I’ll see what science has to say about how to make the perfect hardboiled egg or golden, airy souffle.

Cooking is chemistry, after all.  And hopefully, learning about the science behind what’s going on in our ovens, refrigerators, and frying pans will make us better cooks.  So come along with me as I bust myths, ask the hard questions, and create a frightening number of dirty dishes.  It’ll be fun!

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