Anybody who has eaten popcorn, which means just about everybody, has wondered what made the corn pop. Likewise, countless millions have no doubt wondered why Rice Krispies snap, crackle and do what they do. Shedding light on these and other mysteries:
Why Popcorn Pops: The moisture deep inside turns to steam and explodes the kernel. But, of course, some kernels fail to pop, or pop to too small a volume, perhaps due to damage during machine shelling. To minimize this, agricultural engineers are working to develop strains that are hardier and release from the cob under less force.
Why Rice Krispies Crackle: The starchy puffs of rice absorb milk unevenly, fracturing the shells. Air bubbles trapped inside are suddenly released, making tiny popping sounds.
On the subject of rice, the instant variety is precooked under high heat and pressure to expand the kernels and open the pores for more ready acquisition of moisture during cooking.
Puffed rice and puffed wheat are shot from puffing "guns." Kernels are placed in pressure cookers that retard boiling of the moisture inside. Suddenly, the pressure is released with a "bang" and flash-boiling of the water vapor puffs the kernels.
Old MacDonald's Computer: In this age of computers, even our foods are being analyzed in terms of bytes and bits.
Are the peas ready for harvesting? Agronomists feed time and temperature equations into microprocessors to calculate "heat units," explains Daryl Lund, professor of food engineering at the University of Wisconsin. When enough units are tallied, it's time to check the peas.
They're tested with a shear-press, which pushes knife blades down through a container-cell of shelled peas and measures the resistance.
Because peas and other vegetables have only a brief "peak time" for harvesting, growers need a ready market for their crop. In fact, says Lund, most fields are contracted for by canning companies, which use computers to keep tabs on planting and harvesting schedules, and changing weather and market conditions.
Still a Favorite 2,000 Years Later: Though carbonated beverages are ancient (the Greeks and Romans drank naturally occurring bubbly mineral waters thousands of years ago), today's soft drinks contain flavorings so complex they're often treated as trade secrets, with distractor chemicals thrown in to confuse competitors.
By the way, when you shake up a bottle of pop, it foams over not because of increased pressure inside (there's 45 pounds of pressure regardless), but due to disturbance of the gas in the liquid, which causes a quicker release of bubbles.
Let's Drink to That: There are more than 200 compounds that go into making up beer flavor, explains Klaus Zastrow, vice president of brewing technical services of Anheuser-Busch. "Since we know what each compound tastes like, once we know which ones are present and in what amounts, we can predict how a beer will taste."
Why does draft beer taste better? If it indeed does, Zastrow feels it is not because bottled beer is pasteurized (requiring heat of up to 140 degrees to kill bacteria) as commonly supposed. It is, Zastrow feels, the relative freshness of draft beer that accounts for its superior quality. Beer is one of the few drinks in the world with a stable foam structure, caused by hops and protein molecules linking together on the skins of the foam bubbles.
Lack of a stable foam would signify poor quality only if grease or oil were present, says Zastrow. Substances can be added to increase foam stability by adding thickness to the drink, but this is only done on cheaper beers.
A Painless Extraction: If your coffee has seemed tastier to you lately, it may be the result of a new decaffeination process called supercritical fluid extraction.
Whereas older methods use an organic solvent to dissolve the caffeine (which may leave behind bitter traces), this newer technique "extracts" the caffeine using tasteless, odorless carbon dioxide under very high pressure and a carefully regulated range of temperatures.
Sublime Freeze-Drying: Sun drying, oldest of known food processes, is still used on figs, prunes and raisins; also grains and coffee beans. But because the sun scorches a bit, freeze-drying has been developed to "trick" the moisture out of certain foods.
Applied mostly to quality items such as strawberries or coffee, or to convenience foods such as camping foods or military rations, this gentler process works on a fairly straightforward principle:
Foods to be dried are frozen, then placed in a vacuum (with maybe a bit of heat added) and the moisture just goes -- it "sublimes." (Sublimation also takes place naturally in our refrigerators when ice cubes "shrink" over a period of months.)
And because the moisture departs as a vapor instead of as a liquid, it does relatively little damage to the food structure and carries out fewer flavor compounds (there are an estimated 200 in some coffees).
Though freeze-drying is consummately modern, the Incas used the basic technique on potatoes back at the time of Christ, by taking them up into the low temperatures and air pressure of the mountains.
Colder-than-Arctic Blasts: Food freezing is a bit trickier than just plunging foods into cold storage.
Obviously, slow freezing (as done at home) and rapid freezing (involving temperatures as low as -320 degrees farenheit) are vastly different. Some foods such as meats are robust enough to stand up OK under slow home freezing, but more texturally temperamental foods, such as strawberries and corn on the cob, don't fare as well, says David Thompson, professor of agricultural engineering and food science and nutrition at the University of Minnesota.
Thompson contends that food quality is usually better maintained using rapid freezing techniques because rapid freezing freezes water into smaller crystals inside the cells, where ice does less damage to the food. However, foods can take on a withered look under these colder-than-Arctic blasts.
Ah, Fresh-baked Apple Pie: Of all textural qualities, probably crispness and juiciness are the most important for consumers, says Alina Szczesniak, principal scientist with central research of General Foods. Crispness in a product increases sales, even if it's not perceived at the conscious level, she says. (Even chewing sounds are important to the eater.)
Textures are often most pleasing in combinations. For instance, fruit-and-fiber cereal mixes plump soft raisins, crunchy nuts and flaky cereal pieces; fresh-baked apple pie combines crispness, flakiness, softness and juiciness.
There's a good deal of psychology in this, Szczesniak insists. Why is it, anyway, that most kids eat one food on their plate at a time, whereas adults skip from meat to potatoes to salad as if evoking contrasting chords in a symphony?
Szczesniak offers a theory: When you go to your first play or opera, you're surprised and delighted. After you've been to a dozen, you're less impressed.
Well, it's the same with foods, she argues. With age, we need more variety of stimuli and frequent rejuvenation. There's a hunger for new flavors, new textures, new foods.