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Fighting slime: Researchers develop bacteria-killing plastic film

Plastic films made with bacteria-killing polymers have been proven effective as a frontline defense — not to mention offense — in the battle against biofilms in food production operations.

A preferred place of residence for pathogens such as Listeria and E. coli, biofilms form easily and are extremely difficult to eradicate, according to the Food and Drug Administration, the Centers for Disease Control and Prevention and the U.S. Department of Agriculture.

Biofilms are aggregates of bacteria that highly increase bacterial resistance to antimicrobials, as well as to disinfectants, according to the American Society of Microbiology.

But, by modifying the polymer matrix of plastic films, researchers have developed a rechargeable disinfecting material that can be applied to conveyor belts, food-contact surfaces, utensils and other equipment and surfaces.

The research team lead by Nitin Nitin, professor and engineer with the departments of Food Science and Technology and Biological and Agricultural Engineering at the University of California-Davis, published its results in the Aug. 11 edition of the journal of the American Society of Microbiology. Also on the research project were Andrea Cossu of the UC-Davis Food Science and Technology department and Yang Si of the UC-Davis division of textile and clothing.

“Currently, we do not have an active approach to continuously prevent deposition of bacteria during food processing operations, and can only remove these deposits after processing — during a cleaning shift. Similar risks exist in the hospital environment,” Nitin said in a news release.

The research was funded by the USDA’s National Institute of Food and Agriculture. It builds on previous work by Nitin and others who have experimented with integrating chemical groups called N-halamines into plastic. N-halamines are composed of a nitrogen and a chlorine atom, in some cases with other elements attached.

“Many food borne disease outbreaks can be traced back to cross-contamination of food with pathogenic bacteria,” Nitin said in the release.

“We tested the modified plastic films using two relevant foodborne pathogens— Escherichia coli and Listeria. The tests were conducted to evaluate prevention of biofilm formation, as well as treatment of pre-formed biofilms.”

The researchers targeted biofilms because they are “the leading cause of cross contamination of food and non-food materials upon contact with contaminated surfaces,” according to the research results published in Applied and Environmental Microbiology.

They not only succeeded in preventing the formation of biofilms by killing bacteria, but the researchers were also able to kill existing biofilms on food production surfaces by applying their modified plastic film.

And it’s rechargeable.  

Depending on the precise composition, the N-halamines can kill bacteria on contact, or by releasing chlorine to kill the bacteria. In the latter cases, bathing the plastic films in bleach can recharge the N-halamines with chlorine,” according to the news release announcing the research.

“Conventional sanitizers are difficult to work with in the food production environment, because access to areas of potential contamination is limited. (But the modified plastic film) can be cast or modeled into different shapes, such as conveyor belts, plastic bins for food transport, … or easily added to existing equipment as a lining material.”

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