Antimicrobial Active Packaging Prepared by Reactive Extrusion of ε-Poly l-lysine with Polypropylene

Active packaging offers a unique approach to improving food quality and safety; yet, there remains a need for translatable production methods. We report synthesis of nonmigratory, antimicrobial active packaging. Polylysine (PL) was grafted onto polypropylene (PP) using a free-radical initiator via reactive extrusion, yielding PP-g-PL. PP-g-PL retained similar hydrophobicity to native PP (native PP 109.2 ± 5.6°; PP-g-PL5 116.1 ± 4.8°), important for desirable product-release properties. The surface orientation of polylysine was monitored by the presence of amine groups, with negligible (1.0 ± 0.3 nmol/cm2) amines on control PP and 4.7 ± 1.3, 7.4 ± 2.2, and 10.6 ± 3.8 nmol/cm2 amines on PP-g-PL prepared with 1%, 2%, and 3% polylysine. The antimicrobial active packaging material enabled a 1-log reduction in P. aeruginosa after 1 h incubation at 37 °C. These results suggest that nonmigratory active packaging can be prepared by reactive extrusion, a scalable technology, with promise in improving food safety and reducing food waste.