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Research: Plant extracts shield food

FAYETTEVILLE, Ark. — Incorporating plant extracts into edible protein film made from soybeans can help protect refrigerated and pre-cooked ready-to-eat food from dangerous bacteria, according to research at the Arkansas Agricultural Experiment Station.

Navam Hettiarachchy, University of Arkansas Division of Agriculture food scientist, said food-borne illness is estimated to affect 6 million to 8 million persons, cause 9,000 deaths, and cost an estimated $5 billion in the United States each year. Listeria monocytogenes is one of the more common bacterium that can cause food-borne illness.

Hettiarachchy has learned how to produce edible films and film solutions from soybean proteins that can be coated right on food products or used in place of plastic wrap for prepackaged foods. These films can be impregnated with antimicrobial agents that inhibit growth of bacteria.

In a related study, she has shown that ginko biloba extract (GBE) can inhibit the growth of Listeria monocytogenes. Adding sodium ethylene diamine tetra acetic acid (EDTA) enhanced the antimicrobial activity of GBE.

"Ginkgo biloba leaf extracts have been used by humans for hundreds of years as a medicine," Hettiarachchy said. "We've demonstrated that combining GBE with EDTA had a synergistic effect on the inhibition of Listeria monocytogenes. The inhibitory effect was more pronounced at a refrigeration temperature of 4 degrees centigrade."

Combining this antimicrobial solution with a protective film can be an effective tool for food safety, she said.

"Soy protein films can function as carriers of antimicrobials that help protect against food-borne illnesses," Hettiarachchy said. "We're trying to learn the properties of protein films that will work best as carriers for time-release of antimicrobials that will inhibit pathogens and extend shelf life of packaged foods."

The films are applied to foods either as a dry film wrapper or as a liquid spray that dries into a protective coating. Because they are edible, very thin and have little or no effect on flavor, they can be prepared and eaten with the food, leaving nothing to remove and throw away.

"Our tests have shown that these edible films can act as suitable carriers for delivering effective antimicrobials to the surfaces of food products," Hettiarachchy said. "They have promising applications for pharmaceuticals, fruits, vegetables and meat products."

Fred Miller is science editor for the Arkansas Agricultural Experiment Station. e-mail:

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