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| Sunday, 31 October 2004 |
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Junior Observer |  |
| News Business Features Editorial
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Say cheese
"There really is no good excuse not to like cheese," says Lloyd Metzger. He's a dairy food chemist at the University of Minnesota, Twin Cities, USA. With thousands of varieties available and more in the works, there's a cheese to fit nearly any taste preference, Metzger says. "If you like stinky cheese, you can find a cheese to fit that flavour profile," he says. "If you like bland cheese, you can find that too". Metzger has developed an especially fine appreciation for cheese. As a scientist who studies this multipurpose food, he makes and tastes cheese in his laboratory two or three times a week. Along with other researchers around the world, Metzger is working to formulate cheeses that are tastier, more nutritious, or easier to make than those now in stores. More than just your taste buds stand to benefit from cheese research. Cheese making is a big business, too. Every year, each person in the United States eats an average of 33 pounds of cheese, according to data published by the Food and Agriculture Organization of the United Nations. Denmark, Greece and France top the list, with 63, 57, and 54 pounds per person, respectively. That's a lot of cheese. Loving cheese is nothing new. People have been making it for at least 5,000 years, maybe longer. The first cheese-makers, most experts agree, were herders in the Middle East who domesticated goats and sheep and figured out how to milk them. Legend has it that someone once stored milk in a saddlebag made from the stomach of an animal. After a while, lumps developed in the milk, thanks to a stomach enzyme in the bag called rennet. The first cheese was born!. Turning liquid milk into a solid food had advantages. Compared to milk, cheese was easy to transport, and it could be stored for a longer time. It also tasted good. The basic process of making cheese hasn't changed much since those first lumps accidentally formed thousands of years ago. Scale is probably the biggest difference. Instead of using animal stomachs to process milk from a few homegrown cows, Metzger says, large cheese companies now use room-sized vats that hold 50,000 gallons of milk. Once in the vat, milk is often heated to kill harmful bacteria. Manufacturers then add rennet, which is extracted from animal stomachs. Proteins in milk normally float around as separate molecules. Rennet makes them stick together. Adding rennet to milk causes proteins in the milk to coagulate (curdle) into lumps, called curds, which can then be cut up into smaller pieces. Within 30 or 40 minutes, the enzyme turns the milk's proteins into gel-like yogurt clumps called curds. Stirring utensils and knives in a machine cut the curds into small pieces. As the mixture becomes more concentrated over the next three to five hours, a liquid called whey seeps out. Companies use whey to make high-protein shakes and other products. For every 100 pounds of milk, 90 pounds of whey escape, leaving just 10 pounds of cheese to chew on. First, though, there's still more work to do. Bacterial cultures and salts go in next. The types that are added determine what kind of cheese you end up with. The variety of milk (including what kind of animal it comes from and what the animal was eating before it was milked) also makes a difference, as do storage conditions. Swiss cheese, for instance, goes through a unique ripening process with a certain type of bacterial culture that generates gas, putting holes in the cheese. Cheddar cheese goes straight into the refrigerator. As the cheddar sits there, however, proteins break down, creating a "sharper" flavour. The longer it sits, the sharper the cheese gets. Sometimes, aging goes on for years. To dig deeper into the science of cheese, Metzger works with a special cheese-making machine. One of his main goals is to develop a mozzarella cheese that melts and stretches the way pizza makers would like it to. It's a search for the "perfect melt". Milk, whether from cows, goats, sheep, or other animals, can be converted into all sorts of cheeses. Yet, as scientific as the process has become, cheese-making in many places remains a work of art, designed to please the eye as well as the palate. Science News for Kids ###### Putting the brakes on light Want to hear something that will blow your mind? Light travels 186,000 miles per second in a vacuum; in Lene Hau's lab, it stops! Everyone knows that light, under normal circumstances, travels 186,000 miles per second. It moves a little slower through air or water, but not by much. In 1999 a teacher at Harvard University named Lene Vestergaard Hau slowed light down to a crawl. Moving scarcely 38 miles an hour, it would have come in last in a race with horses. In 2001, she managed to stop it completely. Then, at the touch of a button, allowed it to continue on its way. Hau and researchers like her work with matter in a state that can only be called "weird". They regularly work with stuff at temperatures only a few hundred billionths of a degree above absolute zero. (That's really REALLY cold!) When things get that cold, even the atoms that make up the matter begin to slow down. This is the world of quantum mechanics, where the laws of classic physics no longer apply. When atoms stop moving, they lose their individual identities and merge into a cloud known as the Bose-Einstein condensate. The atoms, now merged into one big atom, begin to move in unison. So how do you stop light? Take two lasers, one magnetic trap, and one small cloud of sodium atom condensate (1/125 of an inch long will do). Capture the substance in the magnetic trap. Aim one beam through the substance (we'll call this the coupling beam). The substance should look transparent now to the naked eye. Take the second laser and send a probe pulse beam through the substance at a right angle to the first beam (This second pulse of light is the light that will be stopped). When the pulse gets half way through the substance, shut off the coupling beam. There. Light has stopped. Wasn't that easy? Here's the cool part, if you switch the coupling beam back on, the pulse continues on its way as if nothing had happened! Smithsonian Magazine Kids' Castle |
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Chances are you love cheese. You might put cheddar on your crackers,
Swiss on your sandwiches, or melted Colby on your hamburgers. You eat
pizza any chance you get.
