A method to prepare an antimicrobial coating for food-handling materials is reported. Alternating layers of branched polyethylenimine and styrene maleic anhydride copolymer were applied onto the surface of polypropylene. The resulting coatings had low surface energy and presented enhanced antimicrobial character due to the presence of both cationic and N-halamine forming structures. In its unchlorinated form, the coating inactivated Listeria monocytogenes by ∼3 logarithmic cycles. In the form of N-halamines >5 logarithmic cycles were reached. Microbial inactivation kinetics showed a Weibullian behavior when the coating was unchlorinated and a sigmoidal behavior when chlorinated. Microscopy confirmed that the reduction in the microbial load was due to biocidal effects of the coating and not bacterial adhesion onto the modified surface. The modified surface was able to be repeatedly rechlorinated. Such rechargeable antimicrobial coatings may support improving food safety by reducing cross-contamination of microorganisms from food-processing equipment.
Keywords: N-halamines; antimicrobial coatings; bacterial adhesion; cationic polymers; inactivation kinetics.