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January 3, 2011

Better Food Safety

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Your Thanksgiving leftovers might get wrapped in plastic, or stored in a container, but before long they'll go bad. Now researchers have created new technology that could significantly extend the life of your food, and improve food safety overall. And as this ScienCentral News video explains, it's also environmentally friendly

Natural Germ Killers

You may not want to eat the plastic-looking wrap , but you certainly might want your cheese packaged in it. Microbiologist Mark Daeschel and engineer Yanyun Zhao made it from natural antimicrobial compounds found in crab shells and egg whites.

"They're not only biodegradable they are also edible," says Zhao. "So there is no environmental impact."

To make these edible films, the Oregon State University researchers combine two natural antimicrobials, lysozyme, a protein found in egg whites that kills bacteria by bursting, or "lysing" their cell walls, and chitosan, a polysaccharide found in crab and shrimp shells.

"These compounds, when they're naturally present in foods, are unavailable to provide any antimicrobial activity," Daeschel explains. "So we have to extract them out, purify them and then fabricate them again."

They tested the films by wrapping or coating fresh produce, eggs and cheeses, then contaminating them. "Then we compare that to food that hasn't been treated with the coating, and we consistently see that the food that has been treated has a much longer shelf life, and we can actually enumerate the death of the microorganisms on the surface of these foods," he says.

They wrote in the Journal of Food Science that the films kill illness-causing bacteria like E. Coli and salmonella
as well as spoilage-causing molds.

Uncoated strawberries after 20 days.
image courtesy Oregon State University
While uncoated strawberries looked like this after 20 days, coated strawberries still looked happy.

"What we can see is a 99 percent or greater reduction in the number of microorganisms within a 24 to 48 hour period," Daeschel says. They also found that consumers reported no changes in the foods' appearance, smell, or taste.

Fresh Focus

Daeschel says the team has focused on foods like fresh produce and dairy products because they are so susceptible to contamination. "Fresh fruits and vegetables have been a problem," he says. "We have had contamination of products like spinach, cantaloupe, lettuce, and also fresh berries. If we can coat these foods and eliminate those microorganisms and provide a safer food, as well as extend the shelf life, that would be a great improvement."

Coated strawberries after 20 days.
image courtesy Oregon State University
"The consumer is looking for more fresh, more natural foods," he says, adding that, "All of the technologies designed to make our food safe may not be appropriate for these new foods."

The researchers are now working with a specialty food company to turn the edible films into products that could be available within a year or two.

Zhao the engineer doesn't see many obstacles to mass-producing the films.

"There are products, in fact, using edible coatings-- some citrus fruits, some apples… are coated by a wax coating. So moving from lab scale to the commercial application for the coating shouldn't be a major challenge," she says. She says the same goes for edible films, which consumers have gotten used to in products like mouthwash strips.

The researchers point out there is a drawback; the films are made from foods that some people are allergic to. Therefore, the films would need to carry warning labels just like all potential food allergens.

Beyond that, they say they see a bright future. "There's no reason why we can't extend it to a whole variety of foods," Daeschel says. "Right now we're at the point of just documenting the ability of the stuff to work on a couple of foods, and then as this becomes commercialized, I'm sure there'll be a lot of different applications with a lot of different foods."

Zhao, who loves to cook and says she makes great Chinese food, expects that her research will be of personal benefit. "I'm a scientist, (but) also a consumer. So I'm very curious, I pay great attention to what I'm eating, and food safety is a big thing," she says "So with this new technology, I really think I'll help consumers, (and) help myself.

This research was published in the Journal of Food Science, October 26, 2007, and funded by Fordras SA, Lugano, Switzerland.

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