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Ice cream man. (Food chemistry: states of matter).

IMAGINE LICKING a double-decker cone and getting a mouthful of coarse ice. That texture may be fine for a snow cone, but for ice cream it's totally wrong! "People expect a smooth, creamy feel without any sharpness on the tongue," says food scientist Douglas Goff at the University of Guelph in Canada. "But there are thousands of ice crystals hiding in a scoop of ice cream." Ice-crystal size dictates ice cream's smoothness. For a velvety mouth-feel, the crystals should be no more than 20 micro-meters (two-hundredths of a millimeter) in diameter. The trouble is, ice crystals tend to grow over time. Let ice cream sit in the freezer for too long and crystals can expand to an unappetizing 100 micrometers in diameter--about the width of a human hair. And the taste? Gross!

The good news for ice cream lovers? Goff has discovered an ingredient that keeps crystals tiny--and may help your ice cream stay as smooth as on the day it was made. The ingredient is a winter-wheat protein (molecule that controls cell growth, among other functions). Called AFP, or antifreeze protein, the molecule directs ice-crystal formation. "Wheat cells produce a variety of ice-modifying proteins in response to cold," says Golf. When an ice crystal forms and grows in a wheat plant, AFPs latch onto the crystal's surface, blocking further growth.

Goff inserted the proteins into a batch of ice cream in his lab, and the proteins had the same ice-modifying effect: Tiny crystals stayed tiny, even when he let the ice cream melt a little before refreezing. Normally, refreezing causes some water to leach out of the ice cream in the form of unpleasantly large ice crystals. If Goff's research continues smoothly, the world's greatest frozen dessert may soon be creamier than ever!

RELATED ARTICLE: Sweet sensation.

When a glob of vanilla ice cream hits your tongue, nerve cells (electrical fibers connected to the brain and spinal cord) detect its cool temperature and creamy texture. At the same time, your tongue's taste-receptor cells (taste buds) kick in. "Each taste bud is an onion-shaped cluster of 50 to 100 taste cells," says scientist Julie Mennella at Philadelphia's Monell Taste Laboratory. The receptor cells, which resemble orange segments, can decipher five tastes: umami (meaty), sour, salty, bitter, and sweet. When ice cream's sugar molecules bind to taste-cell proteins--molecules that can control chemical reactions--the cells secrete chemicals that ferry electrical signals to nerve cells. In turn, the nerve cells transmit the information to the brain, which interprets the message: Sweet!
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Publication:Science World
Article Type:Brief Article
Geographic Code:1USA
Date:May 6, 2002
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