Contact-killing antimicrobial cationic starch/PBAT blown films: Physicochemical properties, antimicrobial mechanism, and preservation capacity on beef

Packaging materials with intrinsic antimicrobial activity can promote food safety and reduce preservatives reliance. Herein, cationic starch (CS) was blended with poly(butylene adipate-co-terephthalate) (PBAT) via extrusion blowing to fabricate composite films. Increasing CS proportions enhanced deformation resistance (69.42%), surface hydrophilicity (32.65%), moisture permeability (70.16%), as well as gas barrier (oxygen permeability reduced by 91.99% and carbon dioxide permeability by 98.48%). CS/PBAT films exhibited contact-killing bactericidal efficiencies of 98.04% and 89.65% against S. aureus and E. coli, respectively, and continuously inhibited their growth within 12-h test. Furthermore, CS/PBAT films showed solvent resistance within 21 days, and no CS migration was observed during 24-h contact on culture medium. Mechanistic studies revealed such effect derived from the electrostatic interactions between quaternary ammonium groups and bacterial membranes, which induced membrane disruption and cytoplasmic leakage. Comprehensive biocompatibility and safety assessment confirmed the biosafety of the films. CS/PBAT films prolonged the shelf life of refrigerated beef to 14 days, suppressing microbial growth, protein degradation, and lipid oxidation. This study offers a novel strategy for designing contact-killing packaging for food preservation.