Archive for the ‘food’ Category
How come when I open a can of mixed nuts, the Brazil nuts (which I don’t even like) are always at the top? asks a reader.
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.
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What causes tea to run down the underside of the spout rather than out of the teapot? asks a reader.
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.
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How does ice cream give you brain freeze? asks Anthony Pena, a student in Woodside, NY.Ice cream, milkshakes, snow cones, frozen Cokes—if icy concoctions cause a stabbing or searing pain across your forehead, you’re not alone: Some 40 to 80 percent of people occasionally get “brain freeze” after eating or drinking something frigid. While your brain doesn’t really freeze, studies show that the temperature in your head does drop when you eat something very cold over a few minutes.
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.
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How come some cereals make a popping sound when you pour on milk? And why do we get white spots on our fingernails? asks Karen Perez, via email.
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.
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Why does ice cream melt? asks Kim Price, via email.
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.
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Why is the cashew the only nut you cannot buy in its shell? asks Russell Judge, via email.
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.
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