Saturday, March 12, 2011
Killer paper for germ-free food packaging
In the future food packaging may include Israeli technology that can keep food free of bacteria.
An 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."
Inquiries from abroad
After the paper was published, Gedanken - who has had a hand in more than 570 such scientific articles -- was surprised by the intense interest this one aroused. A large number of companies have contacted him about it, mostly from the United States and one from the United Kingdom.
Any commercial development of the invention would be handled by Bar-Ilan Research & Development, the corporate interface between scientific and technological development at the university and the world of business and industry.
"The application is straightforward in its ability to elongate shelf life, especially for products such as packaged meat," Gedanken says. "Yesterday I wrote to one company explaining that they can send us a trial of paper to coat with nanoparticles using our machine."
Instead of silver, however, the scientists have switched to zinc oxide, a gentler and highly effective bacteria killer that is favored by the US Food and Drug Administration over silver.
Zinc oxide is also the substance Gedanken is using for his antibacterial textile, which has recently been proven to remain embedded after many washings. The trials, as well as the design and manufacture of machinery to mass produce the fabric, are taking place under the auspices of a large European consortium headed by Gedanken "toward our dream of having a hospital free of bacteria."
Two machines are now being assembled in the Italian headquarters of Klopman International. "A year or so of experiments will take place to gauge performance," says Gedanken. A second machine is being installed in Romania.
Gedanken notes that many other scientists are scrambling to develop antibacterial products like BINA has turned out, largely in response to "superbugs" against which current antibiotics are helpless. But as one multibillion corporation executive told him, none of the others survive washing.
"So we are pretty sure our product is unique," says Gedanken, who hints at many more projects in the pipeline at his university's lab.