Extruded Blends of Chitosan and Ethylene Copolymers for Antimicrobial Packaging

SUMMARY 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® 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 © 2011 John Wiley & Sons, Ltd. It was demonstrated that chitosan can be melt‐processed with an ethylene methyl acrylate copolymer ionomer or with an ethylene vinyl acetate copolymer to create antimicrobial extruded films. The key to a successful antimicrobial blend is to use the solid chitosonium acetate that remains after evaporating water from a chitosan solution, as opposed to using the original chitosan powder that had never been dissolved in dilute acetic acid.