Antimicrobial Activity of Chitosan Attached to Ethylene Copolymer Films

Ethylene copolymer film was coated with chitosan by attachment of the polymer to the corona-treated surface of the film, and the composite film was analysed for antimicrobial activity. The film was active against bacteria in 0.625 mM phosphate buffer; it reduced colony counts of Escherichia coli 25922 and of Listeria monocytogenes Scott A by 5 and 2-3 log(10), respectively after 24 h exposure. The activity of the chitosan-coated film against bacteria in buffer was increased when silver ions were incorporated into the films as demonstrated by complete killing of Escherichia coli O157:H7 DD3795 and the chicken exudate isolate Stenotrophomonas maltophilia within 2 h in buffer. The film was active against L. monocytogenes Scott A in 0.5% buffered peptone water up to a pH of about 7.0. Tests on beef and chicken meat exudates revealed antimicrobial activity of the film against Escherichia coli O157:H7 and L. monocytogenes Scott A of about 2 and 12 log(10) reductions in colony-forming units, respectively. The antimicrobial activity of the film against L. monocytogenes Scott A was also tested on turkey breast, and a log(10) reduction of about 1.7 log(10) units after 10 days and 1.2 log(10) after 15 days at 4 degrees C was achieved. Exposure to chitosan-coated film and 350 MPa of pressure, 55 degrees C or 1% sodium diacetate resulted in a synergistic effect. Copyright (C) 2008 John Wiley & Sons, Ltd.