Project looks at surface changes, coatings to reduce biofilms

Project looks at surface changes, coatings to reduce biofilms

A University of Massachusetts research group has teamed up with the U.S. Department of Agriculture to look at whether combining physical changes to food contact surfaces with Food and Drug Administration-registered coatings may reduce Listeria biofilm formation and potential cross-contamination.

"Our primary goal is to find the right (food contact substance or FCS) coatings and also develop ways to modify the substrates," said Boce Zhang, Ph.D., who is leading the research at the university's Lowell campus for the project titled "Non-fouling food contact surfaces - prevention of biofilm and surface-mediated cross-contamination."

Despite produce industry interest in fouling of FCS, Zhang said the non-fouling properties have not been extensively evaluated. He said he hopes this research will fill in data gaps and provide the produce industry with applicable post-harvest preventive control measures to enhance the non-fouling properties of FCS against Listeria monocytogenes biofilm formation.

Joining him as co-principal investigator in the project is Yaguang (Sunny) Luo, Ph.D. She brings extensive experience in food safety and preventive controls as acting research leader at the USDA Agricultural Research Service's Food Quality Laboratory & Environmental Microbial and Food Safety Laboratory in Beltsville, Maryland. The co-investigators of this project are Dr. Patricia Millner, an expert in food microbiology at USDA, and Dr. Arne Pearlstein, an expert in fluid dynamics at the University of Illinois.

Even if they are successful, the physical modifications and coatings also must be feasible and cost-effective, Zhang said. To that end, the researchers are working with a fresh-cut processor and a food equipment manufacturer to ensure the results are applicable to the produce industry.

Biofilms have become the focus of more research recently because of their resistance to sanitizer treatments. Communities of microorganisms secrete glue-like substances, allowing them to adhere to surfaces. Not only does this film reduce the organisms' chances of being displaced but it also offers protection from some antimicrobials.

Nearly one year into the two-year project, Zhang said they have screened about 20 FCS coatings for efficacy against Listeria monocytogenes biofilm formation. To be candidates, the materials had to already be vetted and registered by the FDA for use in the food supply chain.

Fortunately, he said, many already are used by other parts of the food industry, such as meat and poultry processors. But they hadn't been screened for performance in a produce facility.

From there, the top two to three performers will be selected for more in-depth studies.

Zhang and his group also are examining whether physical changes, such as etching of a material's surface, could reduce biofilm formation. The practice, commonly used on submerged ship hulls, creates a super-hydrophobic coating. Essentially, a thin layer of air bubbles protects the surface and prevents pathogens from attaching.

Zhang and his team will then assess whether applying an FDA-registered FCS coating to physically modified material surfaces further enhances non-fouling properties. This is where input from the cooperating food equipment manufacturer and coating suppliers will be invaluable.

"When they apply coatings, there are different ways to apply them," Zhang said. "And there are different materials that are more easily applied on a flat surface or a complex surface. These are some of the issues where we'll need their input."

Although this project focuses on Listeria biofilm formation, Zhang said treated test materials will be subjected to cocktails that also contain E. coli O157:H7, Pseudomonas fluorescens and/or Ralstonia insidiosa. The latter two organisms have been identified as top biofilm formers among microorganisms associated with leafy greens.

"When you have a combination of different bacteria, the amount of biofilm expands significantly, and that's definitely a risk factor," he said.

Once the researchers have completed their laboratory screenings, they will validate the results in a pilot-scale fresh-cut processing plant operated by USDA in Beltsville, MD. Zhang said he hopes the project results in recommendations for new equipment being coated with FDA-registered FCS in produce processing facilities.

"That's easy to modify - they just choose the right stainless-steel finish," he said. "We're thinking that this will not be a recommendation to coat the entire processing line, but rather to coat high-risk components, and maintain cost-effectiveness."

The results also could be used by plant operators considering retrofits, Zhang said. They may be able to avoid the cost of installing all new equipment by instead applying a benign chemical coating to high-risk surfaces of their existing equipment to reduce biofilm development.

Project abstract may be found on the Center for Produce Safety website on the Funded Research Projects page:

Non-fouling food contact surfaces - prevention of biofilm and surface-mediated cross-contamination