Apr. 2, 2007 Chemists at the University of South Carolina are developing a consumer test kit that people can use to quickly and accurately determine if food products are spoiled or safe to eat.
Described at the 233rd national meeting of the American Chemical Society, the new diagnostic test, which researchers describe as a disposable "dipstick," is capable of rapidly (less than 5 minutes) detecting the presence of chemicals formed by disease-causing bacteria. In preliminary studies, the test had a 90 percent accuracy rate, the researchers say. The test could help avoid illnesses and even deaths caused by food poisoning, which afflicts several million people each year in the United States alone.
The dipstick test is still in development but could be on store shelves in two to three years, says study leader John J. Lavigne, Ph.D., an assistant professor in the school's Department of Chemistry and Biochemistry, located in Columbia, S.C.
"There's no other test like this targeting the consumer market right now that I am aware of," says Lavigne. "It has the potential to change the way individual diners think about the quality of their food and greatly impact public health."
Lavigne envisions that consumers will be able to carry the dipsticks with them and use them anywhere, including homes and restaurants.
The new test relies on the detection of a class of chemicals called nonvolatile biogenic amines. These compounds are generated during the bacterial decay of food proteins and are an indirect measurement of the extent of food spoilage. Lavigne and his associates developed special polymers that change color in the presence of these biogenic amines. In lab studies, they tested these polymer biosensors against a variety of fish samples, including fresh salmon, fresh tuna and canned tuna.
The polymers change color in the presence of increasing levels of these biogenic amines to indicate degrees of food spoilage. Specifically, the polymers changed from dark purple to yellow in the presence of badly spoiled fish, while the change was from dark purple to a reddish hue in the presence of mildly spoiled fish, he says. Depending on the degree of freshness identified, the consumer could then decide whether to eat the food or avoid it. To the consumer, the yellow color would clearly be an indication to avoid the fish, Lavigne says. The test is currently designed to be qualitative only and will not identify the specific pathogen present, he notes.
Although fish were used in this study, a similar approach can be applied to other foods, including other meats as well as fruits and vegetables, according to Lavigne. Although many fruits and vegetables contain lower protein levels than meats, preliminary studies also indicate the dipsticks are capable of detecting even small amounts of protein decay caused by bacterial activity, he says. More detailed tests on these other food types are planned.
Other than tell-tale clues of food spoilage such as foul smells and the appearance of mold, spoilage sometimes can be difficult to detect by the average consumer. Current scientific methods used to identify foodborne pathogens often require expensive equipment, are time consuming (ranging from hours to days) and involve complicated analyses carried out by trained professionals.
The researchers are working to improve the speed, sensitivity and accuracy of the new test. But Lavigne notes that no 'freshness' test will substitute for the importance of proper food safety, including optimal storage, cleaning and cooking. Funding for the study was provided by the University of South Carolina and Research Corporation, a private foundation that advances scientific research.
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