Spaghetti cooking

Before you is a pile of dry spaghetti.  Your job, should you decide to accept it, is to break each piece in half, so that the pasta fits easily into a small saucepan.  Ready, set, snap…Oops.  What should be a snap is actually frustratingly difficult, as tiny, broken bits of pasta litter the table.

Scientists tried to solve the broken pasta problem for years.  Most famously, the late physicist (and Nobel Prize winner) Richard Feynman spent an evening with friend (and supercomputer expert) W. Daniel Hillis, snapping spaghetti.  At the end of the night, there was a pile of broken spaghetti, but no satisfying theory.

But in 2005, two physicists in Paris may have solved the spaghetti puzzle.  The scientists took high-speed images of breaking spaghetti, and applied a mathematical equation describing how waves travel through a stressed object.  What they found:  As a piece of spaghetti is bent until it can curve no longer, it breaks.  The sudden release causes a burst of “flexural waves” to travel through the remaining pieces, causing them to curve sharply, too — leading to more breaking.

So in a split second, your pasta breaks into three or four pieces, instead of neatly in two.  (Watch dry spaghetti bend and fragment at www.youtube.com/watch?v=8GutricnMNc.)

Once you’ve cooked your broken (or intact) spaghetti and added sauce, you may be in the mood for slurping.  But while it’s fun to hoover up strands of spaghetti,  you could find the tablecloth–and everyone around you–covered in a fine spray of crushed tomatoes.

How come?  According to physicist Jearl Walker, of Cleveland State University, the culprit is…wait for it…the Spaghetti Effect.  It turns out that the Spaghetti Effect doesn’t just apply to pasta drawn into your mouth, but also to paper, metal, and other materials pulled into machinery.

Walker says that when a spaghetti strand is lifted from your plate, it already has some sideways swinging motion.  As you suck up the spaghetti, you leave less and less of the strand hanging free.  So the energy of motion–the kinetic energy of the strand — is concentrated in a smaller and smaller piece of strand.  Just before the strand disappears into your mouth, its sideways motion becomes violent enough to fling sauce across the table.

You can also see the Spaghetti Effect in action between meals, whenever you use the vacuum cleaner.  After you’re finished sweeping the living room, unplug the vacuum and press the cord rewind button.  As the spaghetti-like cord is sucked quickly into the base, it may begin to whip around, turning the metal-tipped plug into a moving hazard.  The solution:  Retract the cord slowly, with several gentle pushes of the button.  (And if you must slurp pasta, try to do it in slow motion.)

Ever add sugar to a cup of microwaved tea, only to have the tea (startlingly) boil over?  Boiling depends on bubbles, and sugar can make hot water more bubbly.

Boiling is evaporation, but fast and furious.  We can actually see the water leaving, as a cloud of steam.  It can take days for a room-temperature glass of water to evaporate, but a small pan of water can boil away in a matter of minutes.  That’s because when water reaches its boiling temperature (212 F. at sea level), it evaporates not just from the surface, but from deep within.

Adding sugar (or other ingredients, like salt) can make extremely hot water boil, or cause already-boiling water to boil faster.  How come?  Boiling begins with bubbles.  The first bubbles to appear on the walls of a heating pan of water are actually air that was dissolved in the water, re-emerging as a gas.  But as the bottom of the pan gets hot, liquid water itself begins to turn to gas.

Water begins forming vapor bubbles at hot spots here and there on the pan bottom.  Steam bubbles form most easily on a rough, uneven surface.  Tiny crevices are ideal “nucleation sites,” places where bubbles can get a foothold and grow.

When steam bubbles inflate, break free, and begin to rise, their journey is short-lived.  As a bubble floats up into cooler water in the middle of the pan, it collapses like a deflated balloon.  Why?  At lower temperatures, a bubble’s pressure drops, allowing the kitchen air — the local part of the Earth’s atmosphere — to crush it.

But when the water’s temperature reaches the boiling point throughout, the pressure in the vapor bubbles increases to that of the air.  Bubbles from down under can then rise to the surface.  Where, with tiny pops, they release their vapor into the air.

When you drop sugar (or salt, or powdered sweetener) into boiling water, the crystals provide a raft of new nucleation spots.  Presto–a crowd of new vapor bubbles forms, creating a short-lived fizzy effect.  But add sugar to microwaved water, and the effect can be much more dramatic.

When you heat a cup of water or tea in the microwave, its temperature can rise several degrees above the boiling point — while the liquid remains still and bubble-free.  Why?  When water isn’t heated from the bottom up, there are fewer hot spots.  Meanwhile, in a smooth glass or ceramic cup, there are few nucleation spots.  The result:  Water can “superheat,” without boiling.

Remove your superheated cup of tea and add sugar — or drop a teabag into superheated water — and the results can be explosive.  Runaway nucleation can cause the tea or water to suddenly boil furiously.  Scalding liquid may pour over the sides of the cup, or even spray into the air.  The lesson:  You can’t tell how hot the water is just by looking.  When in doubt, let microwaved liquids sit a while before moving.

It’s the heartbreak of dropped toast.  You tip your plate or lose your grip or bump the table.  In the blink of an eye, your toast is, well, toast: the buttered side stuck to the floor, its surface studded with dust, grit, and cat hair.

But don’t blame the cow.  Toast also lands jam-side down, peanut butter-side down, and, in the U.K., Marmite-side down.

The falling toast effect is one of the most popular examples of Murphy’s Law:  that whatever can go wrong, will.  People have been dropping their buttered toast on the unforgiving floor (and complaining about it) for centuries.  In 1841, an Ohio newspaper called The Huron Reflector published a bread lament:

“I never had a slice of bread, Particularly large and wide, That did not fall upon the floor, And always on the buttered side.”

By the end of the 20th century, science had caught up with what the rest of us already suspected.  U.K. researcher Robert Matthews conducted a scientific investigation of the dynamics of buttered toast.  The result was a 1995 report in the European Journal of Physics, “Tumbling toast, Murphy’s Law, and the fundamental constants.”

In the paper, Matthews noted that the prevailing view among scientists at the time was that there was no toast problem.  Like flipping a coin, toast dropped enough times should land 50 percent of the time on the plain side, 50 percent on the spread side.

And a BBC science show experiment in the early 1990s seemed to support that conclusion.  Volunteers threw their toast into the air.  Of 300 tosses, 152 landed butter-side down, 148 butter-side up.  The conclusion:  the chances of buttering your floor are about 50-50.

But Matthews found this wasn’t the case.  In real life, toast isn’t tossed up into the air.  Instead, it slips off a table or a plate, and usually does land on the buttered side.

How come?  While it seems like the weight of the butter or other spread is to blame, Matthews says it’s the height the toast falls from that’s crucial.   When toast — resting buttered-side up — slips off a standard-height table, it tends to flip over.  Why?  When the center of the slice — which is the center of gravity, if the toast is buttered evenly — moves beyond the edge of the table, the toast begins to rotate over the edge.

If the distance to the floor isn’t far, the toast won’t have time to do a full 360 in the air.  So toast falling about 3 feet usually lands butter-side down.  If the toast has far to fall, it could go either way:  angular momentum will cause it to spin end-over-end, but air resistance will slow it down.  And if it happens to spin, say, 1.5 times, it’s buttered linoleum all over again.

The tumbling toast effect, Matthew says, “seems to be an ineluctable feature of our universe.”

For more toast experiments, visit www.thenakedscientists.com/HTML/content/kitchenscience/exp/butter-side-down.

Did you ever pour a packet of cocoa mix into a cup of hot water…and notice that the pitch of your spoon striking the cup seemed to rise or lower as the mix dissolved?  If so, you’re familiar with the Hot Chocolate Effect.  The strangely musical effect can also occur with instant coffee, or when we add powdered creamer to coffee or tea, spoon sugar into a hot drink, or even drop a scoop of ice cream into a mug of root beer.

To listen for the hot chocolate effect, you’ll need a metal or wooden spoon; use either end.  (You can also use your knuckle, and rap against the outside of the cup.)  After filling the cup with hot water or milk, quickly tap the bottom or side of the cup before adding cocoa.  That way, you’ll tune into the mug’s powder-free sound.

Now add the cocoa, and keep tapping.  You should hear the pitch of the tap first drop, and then begin to rise.  How come?

Physicist Frank Crawford explained why in a 1982 article in the American Journal of Physics.  Crawford dubbed it The Hot Chocolate Effect, and since then, researchers have expanded on his original explanation.  (Read about engineer Kevin Kilty’s experiments with “the cheap instant coffee effect” at www.kilty.com/coffee.htm.)

Scientists say that when you add cocoa to your cup, some of the air dissolved in the hot water gloms onto the powder grains.  The result is tiny bubbles, clinging to the powder.  In other words, foam.  The cloud of foam reduces the speed of sound through the liquid.  Meanwhile, the frequency at which sound resonates inside the mug depends on the sound wave’s speed.  The lower the speed, the lower the frequency.

So when you first add cocoa powder, sounds will actually decrease in frequency.  Since the frequency determines a sound’s pitch, your tapping spoon will sound up to an octave lower than it did in plain hot water.  (Think low thunk.)

But as the bubbles float to the surface and pop, the sound traveling through the cocoa quickly speeds up.  The frequency of the sound begins to rise, and along with it, the pitch.  And so we hear higher and higher notes with each new, now-tinkly tap.  Astonishingly, the pitch can rise up to three octaves, or about the vocal range of a well-trained singer.

(Watch a video of the effect using instant coffee at www.youtube.com/watch?v=JCVaOzlOUfY.)

Experiments to try yourself:  Does the composition (glass, ceramic, plastic) or thickness of the cup make a difference in the changing pitch?  What about a taller or shorter cup or glass?  How about a cup with or without a handle?  (Try tapping on the cup’s bottom, then on or near the handle.)  Does using different liquids (water, skim milk, whole milk) alter the sound?  Finally, what about adding whipped cream or marshmallows?  At the very least, it’s all a good excuse to make a second (or third) cup of cocoa on a cold winter’s day.

It’s like a Brazil nut conspiracy. The big, heavy nuts sit like bullying boulders at the top of the can, shoving all the tasty almonds, pecans, cashews, and (not-so-thrilling) peanuts to the bottom. Doesn’t gravity make heavier things sink? Or is it somehow rendered powerless in the confines of a Planters can?

Scientists first officially identified the mystery in the 1930s, around the same time the first Planters peanut stores opened across the U.S. When a container of particles is shaken up and down, a big particle buried inside will tend to rise to the surface.

More than 70 years later, the Brazil Nut Effect still isn’t completely understood. Why all the attention to a problem with party nuts? Scientists say that the Brazil Nut Effect goes way beyond oppressed almonds. The separation of a material’s particles by size affects everything from geological processes to food and drug manufacturing. On the positive side, the effect allows manufacturers to use vibration to separate particles (like grains of rice) by size. On the negative side, it can result in unevenly-mixed medicine.

The Brazil Nut Effect also interests scientists investigating the effects of vibration on sand and snow, and how materials sort during avalanches and landslides. Meanwhile, farmers encounter the effect every spring, when boulders mysteriously appear on open fields, heaved up through the freezing/thawing ground.

The oldest explanation for the effect is also the simplest. With each vertical shake or jostle (say, in a truck on a bumpy road), particles rise off the bottom and then settle. As spaces are created in the material, smaller particles in a container sift down into the gaps under bigger particles. Gradually, the biggest particles are pushed to the top.

But there’s more: Material that is thrown against the container walls experiences friction, and a stream of small particles flows downward along the walls. Meanwhile, in the center, particles heave up, like spaghetti in a pan of rolling boiling water. The big particles can’t return to the bottom through the narrow margins along the side walls. So they remain stuck at the top.

Scientists have also discovered that how fast a nut rises through, say, a box of cereal flakes also involves air in the spaces between particles. Air apparently causes a drag on the smallest particles, keeping them from rising as quickly. In experiments using an air-free vacuum, all the particles, big and small, moved toward the top at the same rate.

To complicate matters, some experiments have shown that big but lightweight particles may actually sink to the bottom, in a kind of reverse Brazil Nut Effect. Meanwhile, other experiments have shown that heavy and lightweight particles rose faster than medium-weight particles of the same size. The upshot? The Brazil Nut Effect is far more complex than anyone imagined 70 — or even 10 — years ago.

Do your own Brazil Nut Effect experiment; visit the website http://199.6.131.12/en/scictr/lab/brazilnut/index.htm.

Whether it’s tea ruining a tablecloth or rain rotting a windowsill, scientists call it The Teapot Effect, and still write and publish papers about the annoying phenomenon. Tea seemingly changes its mind about being poured into your waiting cup, turning back to run down the spout. But gravity has the last laugh, as the liquid breaks off the teapot and drips unceremoniously onto the table.

And it’s not just tea. If you’ve ever tried to pour milk into your cereal from a drinking glass, you know that it sometimes takes a side trip down the glass. From rainwater pooling underneath outdoor windowsills to soup running down the pan and into the burner, the teapot effect is a pesky problem in fluid dynamics.

So what’s the story behind tea’s messy retreat? Some theories say the teapot effect is due mainly to surface tension and adhesion. The molecules at the surface of a liquid are attracted much more strongly to each other than they are to molecules in the air above. The result is surface tension, creating a kind of elastic “skin,” allowing some insects to walk across ponds. Surface tension also causes water to bead up on wax paper or other surfaces. Meanwhile, water is also attracted to other materials, causing it to cling a bit to glass and ceramic vessels.

But according to physicist Jearl Walker, of Cleveland State University, the key factor in the teapot effect is the pressure of air, varying across the flowing tea. A stream of tea experiences higher pressure where its exposed surface meets the air, and lower pressure underneath, where the out-flowing tea touches the lip of the spout. If the stream is flowing slowly, the higher air pressure from above causes the tea to run down the underside of the spout, rather than arcing gracefully into your cup.

Walker and others say that air pressure trumps adhesion. He notes that coating the underside of the spout with butter to reduce wetting does nothing to prevent sluggishly flowing liquid from taking its drippy detour.

So how to prevent the dribble? British engineer Damini Kumar noticed that outdoor windowsills often have a built-in groove underneath, preventing dripping rainwater from taking a damaging detour back into a building. So she designed a dripless teapot spout with a similar groove on the underside. The spout also narrows at the end, forcing the tea to flow faster as it exits.

But you can usually avoid the dreaded runback with good pouring technique. According to Jearl Walker (and generations of tea pourers), the trick is to pour quickly, so that the liquid follows a “projectile path” through the air above the cup. Then, like a circus performer shot from a cannon, the tea should land in the cup, rather than sliding back down the pot.

For more on the teapot effect, see http://news.bbc.co.uk/2/hi/science/nature/227572.stm.

Up to 93 percent of migraine sufferers say they also get ice cream headaches. But even the normally headache-free often suffer a brain freeze attack at the local Baskin-Robbins. The pain usually peaks in a minute, and then quickly fades. Theories abound about what, exactly, causes the stabbing pain. Some say the headache is a referred pain from iced nerves in the palate and throat. Others say that blood vessels in the mouth and throat, constricted by the cold, cause blood vessels in the rest of the head to expand, triggering a headache.

However, many have noted that they don’t have to be eating anything to get brain freeze. A faceful of snow during a winter snowball fight, a blast of icy wind on an exposed forehead, or a slap in the face by a cold ocean wave can produce the same brief, excruciating pain as chugging a milkshake.

One researcher used an ultrasound machine to track blood flow in the brain during ice cream headaches. He found that blood flow temporarily decreased, indicating cerebral arteries were constricting. But no one knows whether the constriction results from chilled blood flowing through the neck to the brain, or from a signal sent by chilled nerves in the palate and throat.

In 2002, an eighth-grade student named Maya Kaczorowski had her own brain freeze experiment published in the British Medical Journal. Maya recruited 145 kids to participate in ice cream-eating sessions. Some ate small amounts of ice cream quickly (in less than 5 seconds); others indulged more slowly.

The result: About 13 percent of the students in the slow group got ice cream headaches, while more than twice as many of the fast eaters experienced the icy pains. And nearly 80 percent reported getting brain freeze sometime in the past. (Read Maya’s full report here.)

More recently, researchers in Japan used the slurpee method to induce headaches in their subjects. The results were presented at the October 2005 meeting of the American Society of Anesthesiologists. Volunteers were asked to eat a whopping 3/4th lb. of shaved ice over 10 minutes. About 2.5 minutes into the experiment, volunteers began to get severe headaches.

During the headaches, the volunteers’ ear temperatures dropped, but armpit temperatures stayed the same. So cooling the throat, and thus the carotid arteries in the neck, may cool the brain without producing a big change in body or heart temperature. That could be a way, the researchers suggest, to protect the brain without hurting the heart while doing life-saving CPR.

While Rice Krispies may be the noisiest cereal, other puffed cereals may also snap, crackle and pop when doused with ice-cold milk. Just as corn is popped into popcorn, rice, wheat, and other grains can be puffed up into fluffier versions of themselves. In the case of puffed rice, cereal makers oven-toast the rice, which has been conditioned with water. As the water turns to steam, rice kernels puff out like microwaved popcorn.

Unlike the compact, hard walls of an uncooked rice kernel, the walls of puffed rice are stretched very thin, making each kernel quite fragile. When cold milk is poured on, the shock causes the walls to crack like a thin glass crystal. As the milk is (unevenly) absorbed by the puffed rice grains, the snapping, crackling and popping sounds come from the fracturing of the walls and the escape of air bubbles trapped inside the kernels.

Meanwhile, if you pick up your spoon to eat your talking cereal and notice a few white spots on your fingernails, don’t panic. Some cultures see the white spots as a good luck sign, and even call them fortune or gift spots. There’s also the old idea that someone with a white spot on a fingernail is in love, or that the number of white spots equals the number of “sweethearts” a girl has. In an Alice Hoffman novel, a white spot appeared on a character’s fingernail each time he lied, a telltale sign like Pinocchio’s growing nose.

But fibbing, falling in love, or winning the lottery actually have nothing to do with white spots, unless you happen to hit one of your fingers in all the excitement. Dermatologists (skin doctors) say that white spots and smeary streaks happen to all of us, and are usually nothing to worry about.

The official name for white nail spots is the somewhat scary-sounding punctate leukonychia. (In total leukonychia, the entire nail turns white.) Kids and adults often have one or more random white dots or marks on their nails, especially if they are hard on their hands. Dermatologists say the spots appear because of repeated dings to the nail bed at the base of a fingernail (say, by a striking ball when playing sports). Much rarer causes include infections, systemic illnesses and dietary deficiencies.

White spots are a mix of keratin (a tough protein) and air. The spots are places where, due to an minor injury to the nail bed, new nail cells were incompletely formed or “keratinized.” The white spots will rise higher as the nail is pushed up by new growth from the nail bed. Since a nail grows about one millimeter in 10 days, it can take months for the spotted part to reach the tip for trimming off. Meanwhile, you can look at your nail spots and relive memories of all the insults and injuries to your fingers in the past year.

Whether premium, low-fat, nonfat, or low-carb, all ice cream melts on a hot summer day, dripping down the cone and onto the front of your shirt.

In melting, ice cream is just behaving like any other bit of frozen, icy matter, suddenly exposed to warm air. Matter changes its state, depending on temperature and pressure. Liquid water boils into a gas (water vapor), freezes into a solid (ice), and melts back into a liquid if left out of the fridge.

But ice cream isn’t plain water, and how (and how fast) it melts depends on more than just temperature. The melting qualities of ice cream are actually a favorite focus of some food scientists, since how ice cream melts affects how it tastes.

If you’ve ever made ice cream at home—or idly read the carton label as you dug in with a spoon—you know ice cream’s basic ingredients: cream and/or milk, sugar, and flavoring, plus egg yolks in the custardy varieties. Some brands add chemical stabilizers and emulsifiers. Finally, there’s the fruit, nuts, chocolate chips, candy, cookie dough, and other extras that create hundreds of flavors.

Scientists call ice cream a frozen foam, since ice cream is partly just thin air. Premium, high-fat ice creams contain the least air, while some bargain brands may be more than half air by volume. (Which is why a pint of Haagen-Dazs usually weighs more than a pint of generic.)

After the cream, milk, sugar, flavorings (and egg yolks) are combined or cooked together, the mixture is transferred to an icy-cold blending machine. Air is whipped in, milk proteins and fat droplets surrounding the air in a honeycomb structure. Ice crystals form throughout the mixture as it freezes. Rotating blades break the crystals into tiny pieces, so that the resulting ice cream has a smooth, non-gritty texture. After final ingredients (from coconut to candy canes) are mixed in, the ice cream is put in the deep freeze to harden at about -40 C (-40 F).

Researchers test the melting rates of different ice creams by putting a scoop on a wire screen in a warm room, measuring the fluid that drips through. Ice cream melts as it absorbs heat from the air, with ice crystals on the outside of the scoop melting first.

Scientists say that the melting rate of ice cream depends mainly on the amount of whipped-in air, the size of its ice crystals, and its framework of fat globules. Airier ice creams (and those containing the additive polysorbate 80) tend to keep their shapes longer in the heat.

But leave the carton out on the counter too long, and your ice cream will suffer the dreaded food-science fate called “heat shock.” Each time ice cream half-melts and then is shoved back into the freezer, its liquid water refreezes around existing ice crystals instead of forming new ones. Over time, ice crystals get bigger and bigger, and your once-creamy treat becomes lumpy, coarse, and crunchy.

For more on melting ice cream, visit this website.

Cashews — the nut that sounds like a sneeze — are the oddballs of the nut world.

Think of nuts on a tree, and you might imagine round walnuts hanging on the branches of a black walnut tree, thudding to the ground in late summer or early fall. But cashews come in an elaborate disguise. A cashew wearing its shell looks exactly like a fat worm, wriggling out the bottom of a misshapen apple.

Evergreen cashew trees grow only in a tropical or subtropical climate. The cashews we eat come mainly from India, Vietnam, Brazil, and a number of countries in Africa, including Nigeria and Tanzania.

Cashew trees can grow to be over 40 feet tall, their green leaves the backdrop for brightly colored cashew apples, the tree’s “false” fruit. Yellow or red cashew “apples” actually look like pears, or oversized hot peppers. The nuts protruding from the apple’s undersides are the tree’s real fruit. Hidden inside each nut is a single seed — a delicious cashew.

Why not pluck the nut and sell it with shell intact — like a walnut, pecan, or almond? The problem lies in the cashew’s family tree. One of the cashew’s close relatives is the pistachio, the tasty green (though often dyed red) nut used for snacks and ice cream. Another is the tropical mango. But other relatives – the black sheep of the Anacardiaceae clan – include the not-so-nice poison sumac and poison ivy.

All of these plants contain urushiols, the oily chemicals that makes a brush with poison ivy such a painfully itchy experience. The cashew’s share of urushiols are concentrated in an oily liquid trapped between the two layers of the shell. (It’s no wonder that an old name for the cashew was “blister nut.”)

Because of the lurking urushiols, cashews must be processed very carefully. Much of the work is still done by hand, and cashew workers often suffer from burning rashes and eye irritation. The process of removing the shells and extracting the liquid includes roasting, burning, boiling, soaking, cracking and peeling. Instead of being discarded, the cashew nutshell liquid (CNSL) is often sold for industrial uses. CNSL oils are used in waterproof paints, varnishes, and lacquers, while CNSL solids are used as friction particles in brake linings.

Finally, the cashew seeds are thoroughly cleaned and roasted. This leaves a batch of pristine (and urushiol-free) cashews, ready to eat.

Despite having poison ivy for a ne’er-do-well first cousin, cashews cause fewer allergic reactions than other nuts. But when cashew processing gets careless, there can be problems. In 1982, more than 50 Pennsylvanians who ate cashews sold by their local Little League ended up with poison-ivy-like rashes. The culprit: bits of cashew shells mixed in with the cashew pieces.

Fortunately, such glitches are rare. Cashews make an excellent snack, containing heart-healthy unsaturated oils as well as a good mix of protein and carbs. To see cashew apples and nuts on the tree, and learn more about their processing, visit this website.