Scientists Harness High Speed Train Technology To Test Food

Scientists say you can measure how much fat is in food and how much salt is in water using the power of magnets.

Futurists take note: Magnetic levitation -- the discovery that was supposed to revolutionize high-speed rail but hasn't really taken off commerically -- might have a more practical and cheaper application.

Scientists have found the technology can be used to take important measurements of our food. For example, whether water is too salty to drink and how much fat is really in that lowfat milk.

So how does it work?

As a kid, you probably impressed your friends with magnet tricks. So you know that the opposite poles attract and the like poles repel each other.

Magnets on the bottom of a maglev train repel magnets on a special rail, and voila, you've got a high-speed, fossil-fuel free ride.

But those train systems are pretty expensive to build. And so far, maglev trains can't run on existing rails. That limits their practicality, particularly in the minds of U.S. officials (This video shows how the trains work.)

But George Whitesides and his colleages at Harvard wanted to shrink that technology down and see what else it could do. They built an ice-cube sized sensor using the same technology to test the density of foods and beverages.

The sensor is a fluid-filled container with magnets at each end. It allows tiny samples of solids or liquids to be placed inside. The distance they migrate through the fluid allows us to measure their density.

The device quickly estimated the salt content of water and the relative fat content in different kinds of milk, cheese, and peanut butter in the lab.

There are other methods of measuring the density of food products already in use, but many are large, expensive, and require highly-specialized technicians to interpret the results, the study says.

This one was relatively easy to read -- the higher in fat the milk or cheese, the higher the materials levitated toward the top magnet, according to the study.

The study appears in the latest issue of Journal of Agricultural and Food Chemistry. Copyright 2010 National Public Radio. To see more, visit http://www.npr.org/.

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