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Killer paper for germ-free food packaging

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Friday, April 1st, 2011

As reported in Israel21CAn Israeli invention could revolutionize the way perishables are packaged, extending shelf life by banishing bacteria.

 Imagine if all the paper, cardboard, foil and plastic that envelops the food we buy could not only keep it clean and tidy but also free of the bacteria that leads to spoilage.

That scenario is quite possible in the near future, thanks to an Israeli student and his master’s thesis supervisors.

Graduate student Ronen Gottesman developed a silver nanoparticle-coated paper with the guidance of Prof. Nina Perkas at Bar-Ilan University’s Institute of Nanotechnology and Advanced Materials (BINA) and Mina and Everard Goodman Faculty of Life Sciences. As reported in Langmuir, the journal of the American Chemical Society, the “killer paper” is intended for use as a new food packaging material. It could provide an easy alternative to preservation methods such as radiation, heat treatment and low temperature storage.

“Metallic silver has been known for generations as an antibacterial agent,” explains Prof. Aharon Gedanken, director of the Kanbar Laboratory of Nanomaterials at BINA. Silver already is widely used as a bacteria fighter in medicinal ointments, kitchen and bathroom surfaces and even odor-resistant socks. Scientists have been exploring the use of silver nanoparticles — each 1/50,000 the width of a human hair — as long-lasting germ-fighting coatings for plastics, fabrics and metals.

“The smaller the size of the particles, the more effective they are against bacteria,” Gedanken tells ISRAEL21c. However, developing a nanoparticle-coated product suitable for commercial use has proven difficult.

Strategies for vanquishing germs

Gedanken, who is spearheading a multi-country project to commercialize an antibacterial textile for hospital use, suggested that his student explore how germ-fighting nanoparticles could be introduced to paper and other food wrappings.

First, Gottesman had to spend a year brushing up on microbiology under the supervision of Prof. Yishayahu Nitzan. “We are chemists, not biologists,” Gedanken explains.

Using silver nanoparticles fabricated at the BINA lab, Gottesman used a sono-chemical technique Gedanken innovated for “throwing” the particles onto paper or textile at such high speed that they become permanently embedded. Then he took the paper to the microbiology lab to test its antibacterial properties.

The coated paper showed potent antibacterial activity against E. coli and S. aureus, two causes of bacterial food poisoning. It killed all of the microbes in just three hours.

“In the future, people could coat any packing material, like plastic bags, paper and cartons, to keep the food fresh for a longer time,” says Gedanken. “It is bacteria that causes food to rot.”

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