Extruded Blends of Chitosan and Ethylene Copolymers for Antimicrobial Packaging

Chitosan was melt-processed with an ethylene methyl acrylate copolymer ionomer and with an ethylene vinyl acetate copolymer to create antimicrobial extruded films. The key to obtaining a successful antimicrobial blend was the use of solid chitosonium acetate that remained after evaporation of water from the chitosan solution. When solid free-flowing powders of chitosonium acetate were formed by spray drying chitosan solutions, blended in an extruder (at 2.5% and 4% chitosan) with Elvax (R) 3175 ethylene vinyl acetate copolymer, and extruded through a film die onto a chill roll to form films, the films exhibited antimicrobial activity against Escherichia coli 25922, Salmonella enterica serovar Enteritidis NalR, and Listeria monocytogenes Scott A. The log10 reductions in CFU/ml after 24 h in a shake-flask test were near 2 for films containing 4% chitosan. This melt-blending/extrusion approach is expected to open applications for chitosan-based antimicrobial packages and articles that were impossible or impractical with chitosan coatings. Copyright (c) 2011 John Wiley & Sons, Ltd.