Control of Listeria monocytogenes on contact and non-contact surfaces by electrostatic spraying of quaternary ammonia

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The attachment of bacteria on food processing equipment and in the environment can cause potential cross- contamination, which can lead to food spoilage, possible food safety concerns, and surface destruction. Food contact surfaces used for food handling, storage or processing as well as environmental surfaces such as drains, walls, and floors are areas where microbial contamination commonly occurs. Even with proper cleaning and sanitation regimes or practices in place, bacteria can remain attached to the surfaces and this attachment can lead to biofilm formation. The purpose of this research was to determine if electrostatic spraying of quaternary ammonium compounds would provide a more efficient means for sanitizing food contact and environmental surfaces to prevent bacterial attachment and biofilm formation compared to conventional application. The surfaces subjected to 200 ppm of ala-quaternary ammonium treatments were ceramic tile, FRP (plastic wall board), polypropylene conveyor belt- mesh top (24% open mesh) and stainless steel conveyor – single loop (80% open mesh). To determine the efficacy of the electrostatic sprayer in comparison to pressure spraying for sanitizing, the surfaces were inoculated with a Listeria monocytogenes cocktail with a final concentration of 106 cfu/ ml. The test surfaces were analyzed with a swab method prior to inoculation, after 1 hr of attachment and after sanitizing treatment. Overall there were significant (P< 0.05) reductions in the amount of LM that remained on the surfaces after being treated with both the electrostatic spray and the air- pressure spray. There were no significant differences in the bacterial loads between the two treatments (P< 0.05).To determine electrostatic spray could prevent biofilm formation, surfaces were treated with quaternary ammonium electrostatic spray or a pressure sprayer. The surfaces that were used were ceramic tile, FRP, stainless steel coupons (306 food grade), and polyethylene (plastic cutting board). After the surfaces were subjected to the treatment, they were allowed to air dry for 30 minutes. The surfaces were then placed in wells containing a Listeria monocytogenes solution with a concentration of 106 cfu/ mL. The test surfaces were analyzed after 24 hrs by crystal method analysis and scanning electron microscopy (SEM). Results from the crystal method analysis indicated that electrostatic spray significantly (P< 0.05) reduced the biofilm formation on all the surfaces. Overall, electrostatic spray of quaternary ammonium provided a more efficient means of biofilm prevention on multiple food contact and non- contact surfaces.

Electrostatic spray, Listeria monocytogenes, Biofilm