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Dipstick Test Detects Spoiled Food

American research team develops a format that spots bacterial breakdown of food

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HealthDay Reporter

MONDAY, March 26, 2007 (HealthDay News) -- Imagine using a "dipstick" test to find out if your food is spoiled.

If things work out as John Lavigne hopes, it just might be possible.

Lavigne, an assistant professor of chemistry and biochemistry at the University of South Carolina, and his research team have developed a polymer sensor that detects biogenic amines, the breakdown products of proteins that are a hallmark of food spoilage.

However, some experts are skeptical, saying it would be hard to improve upon good, old-fashioned food hygiene and a sensitive nose.

The findings were presented Sunday in Chicago at the American Chemical Society's national meeting.

Targeting nonvolatile amines -- the breakdown products that you cannot smell -- the test is about 90 percent accurate, Lavigne said, and can detect spoilage in different kinds of meats, vegetables, fruits and beverages.

"Hundreds, thousands, millions of people per year in the U.S. get sick, because they cannot tell when food goes bad. So, there's a lot of opportunity out there to short circuit some of these illnesses," Lavigne said.

The test works much as pH paper does. A small sample of what Lavigne called "the food's natural liquid" (his team used fish) is added to a purplish, dark-red solution of polymer. If the food is starting to turn, the solution changes color, from red to orange to yellow, depending on the extent of spoilage.

Though the test is currently solution-based, Lavigne is working on a dipstick test for consumer use. "There are a couple of different formats that we're looking at," he said. "All would require a small, liquid-based sample from the food. If it's a beverage, that's easy. If it's chicken or fish, we're working on developing a method to very easily extract a small bit of liquid and directly introduce it into the sensor."

Lavigne described the current format as "very discrete," pencil-sized, but shorter.

Some experts questioned the utility of the system.

"What's wrong with your nose?" asked Philip M. Tierno, director of Clinical Microbiology & Immunology and associate professor of Microbiology & Pathology at New York University Medical Center. "Your nose is a very sensitive mechanical device that can detect amines. If it's bad, you'll know it."

Tierno, who did call the findings "a great beginning," said that when food spoils, both volatile and nonvolatile amines are produced. "A dead carcass will not decide which kind to display, both are present. Whether your system detects one or another, it doesn't matter."

Dr. Pascal James Imperato, chairman of the department of preventive medicine and community health at SUNY Downstate Medical Center and former commissioner of health for New York City, noted that a negative result in this test does not mean the food is safe to eat raw.

That's because the test only detects the products caused by bacterial breakdown of food as the bacteria "eat" it. Some pathogens don't "ingest" the food they inhabit, and even if they do, that breakdown will be slow if the food is properly refrigerated.

"All it is doing is measuring degradation of protein due to spoilage. So, if the test is negative, that doesn't mean the food isn't contaminated with toxicogenic E. coli, salmonella, staphylococcus or any other microbe."

Indeed, Imperato said, a test such as this could not have prevented the recent E. coli outbreak linked to contaminated spinach, for instance, because the pathogens were not breaking down the leaves. "Very often, these organisms are simply on the surface of the vegetables but not attacking the plant," he explained.

Earlier this month, the U.S. Food and Drug Administration unveiled a draft of new voluntary guidelines for commercial processing and handling of fresh-cut vegetables and fruit to minimize such outbreaks.

In the meantime, the best way to prevent food poisoning, Tierno said, is to consider all food potentially pathogenic. "If you practice good food hygiene, and you cook your food well, you will kill potential pathogens, whether a parasite in the fish, or a [bacteria] in the fish, or E. coli in meat.

"In public health," Imperato said, "there is an old adage: When in doubt, throw it out."

More information

For more information on food handling, visit the U.S. Department of Agriculture.

SOURCES: John Lavigne, Ph.D., assistant professor, chemistry and biochemistry, University of South Carolina, Columbia; Philip M. Tierno, Ph.D., director, Clinical Microbiology & Immunology, and associate professor, microbiology & pathology, New York University Medical Center; Pascal James Imperato, M.D., distinguished service professor, chairman, preventive medicine and community health, and director, Master of Public Health Program, SUNY Downstate Medical Center, New York City; March 25, 2007, presentation, American Chemical Society annual meeting, Chicago

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