Bacteria-killing paper for next-generation food packaging

BANGALORE - Food could get a longer shelf life using “killer paper,” a new packaging material made of anti-bacterial nanoparticles, scientists at Israel’s Bar-Ilan University have reported.

Aharon Gedanken and colleagues at the university’s chemistry department claim to have developed and successfully tested the “killer paper,” that they say helps preserve foods by fighting the bacteria that cause spoilage. The finding has been reported in Langmuir, a journal published by the American Chemical Society (ACS).

According to the report, the killer paper contains a coating of silver nanoparticles which are powerful anti-bacterial agents. Silver already finds wide use as a bacteria fighter in certain medicinal ointments and bathroom cleaners and scientists have been exploring the use of silver nanoparticles as germ-fighting coatings for plastics and fabrics, the ACS said in a statement.

It said that the “killer paper” coated with silver nanoparticles “could provide an alternative to common food preservation methods such as radiation”.

According to the Israeli researchers, silver nanoparticles could potentially help overcome the growing problem of antibiotic resistance in which bacteria develop the ability to shrug-off existing antibiotics.

In laboratory experiments they demonstrated that the coated paper’s potent antibacterial activity against E. coli and S. aureus, two types of bacteria that usually cause food poisoning. “These organisms were killed by the killer paper in just three hours,” the scientists reported suggesting its potential application as a food packaging material for promoting longer shelf life.

Producing killer paper that is suitable for commercial use was however not easy. In their paper, the scientists describe development of an effective, long-lasting method for depositing silver nanoparticles on the surface of paper by using ultrasound - high-frequency sound - waves.

The researchers described their ultrasound procedure as a new, simple, one-step process that involves generation of silver nanoparticles in the reaction vessel and their simultaneous deposition as “microjets” onto the surface of the paper.

They said the technique allows the thickness of the coating and the particle size of the nanoparticle to be controlled to a great extent. “Moreover, formation of a robust coating as a result of ultrasonication results in long lasting coating with extended lifetime and antibacterial properties.”

According to their report, the sonochemical process used in their study can be extended to other nanomaterials on similar substrates to achieve different functionalities for various other applications. “The simplicity of the procedure means that such a method could be easily scaled up to meet the requirements of large scale coatings,” the researchers noted.