Thursday, Oct 23, 2014
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Edible film from fungus fights food pathogens


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In an effort to help the producers of many types of processed foods keep the good stuff in and the bad stuff out, researchers at Penn State University have been experimenting with an edible film created from a polymer produced by a type of fungus.

Although it isn’t going to replace the plastic packaging in wide use in the food industry, the film can play a role in preserving food’s flavor, freshness and color, and keep bacteria and other pathogens at bay, according to Catherine Cutter, professor of food science at the Penn State College of Agricultural Sciences.

Writing in the April issue of the Journal of Food Science, Cutter and her colleagues report a film containing 2 percent essential oils derived from the herbs rosemary and oregano and nanoparticles made from zinc oxide or silver was able to significantly inhibit the growth of pathogens.

The essential oils and nanoparticles are added to a polymer film created by Aureobasidium pullulans, a yeastlike black fungus found in a variety of fruits and vegetables.

The pullulan film, when applied to food, can slowly release pathogen fighters such as the essentials oils and nanoparticles, the Penn State researchers say.

“The results from this study demonstrated that edible films made from pullulan and incorporated with essential oils or nanoparticles have the potential to improve the safety of refrigerated, fresh or further-processed meat and poultry products,” said Cutter.

The film’s pathogen fighting abilities were tested in experiments in which the film was placed in laboratory Petri dishes and then applied to fresh and ready-to-eat meat and poultry products containing bacterial pathogens.

These experimented were led by Mohamed Morsy, a doctoral student at Benha University in Egypt. He was at Penn State on a Borlaug Fellowship through a USDA-Foreign Agricultural Service grant.

The film is more effective in fighting food pathogens than spray-on antimicrobial agents, Cutter and her colleagues believe, because the liquid can run off the food without being absorbed.

The film clings to the food, allowing the pathogen fighters to be released over time.

The edible film is no immediate threat to supplant plastic food packaging, Cutter acknowledges, because the film is not as impermeable to oxygen than plastic.

“The meat industry likes the properties of the polyethylene vacuum packaging materials that they are using now,” she said.

Undaunted, Cutter thinks combining the two materials may be a viable approach. So she is going to try to develop a two-layer packaging. “I keep thinking there’s a way to extrude edible, antimicrobial film in one layer with polyethylene, creating all-in-one packaging,” Cutter said.

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