Antimicrobial polymer coatings with efficacy against pathogenic and spoilage microorganisms

Antimicrobial polymer coatings with inherent self-sanitizing properties have been explored to support food safety and preservation. Materials with multiple antimicrobial modes of action represent a novel alternative. Herein, we evaluated the antimicrobial effect and storage stability of coatings with varied molecular weight styrene maleic anhydride (SMA) cross-linkers (6, 8, 120, and 250 kDa) and branched polyethyleneimine (PEI) coated onto polypropylene films. Infrared spectroscopy analyses suggested successful crosslinking between all varieties of SMA and PEI. Coatings were evaluated in their inherent form (cationic), and chlorinated as N-halamines. Surface concentration of primary amines ranged from 350 to 900 nmol/cm2, and N-halamine concentration ranged from 90 to 130 nmol/cm2, with values varying depending on SMA molecular weight. Surface energy decreased with increasing molecular weight of SMA. Optimal cross-linker molecular weight was determined based on antimicrobial performance, where the coated PP with 6 kDa SMA demonstrated enhanced biocidal effect against Escherichia coli O157:H7 in its chlorinated form. Further, the antimicrobial coating demonstrated efficacy between ∼3 and >5 logarithmic reductions in its unchlorinated and chlorinated forms against Escherichia coli O157:H7, Listeria monocytogenes, and Pseudomonas fluorescens. Storage studies supported the stability of the chlorinated N-halamines, with full chlorine retention over a 24 h study.