Development of Chitosan-Based Antimicrobial Nanocomposite Films for Extending the Shelf Life of Perishable Food Products

Abstract

Fruits, meats, and fish go bad within days, whereas the plastics covering them can live hundreds of years past their expiration date. Could we use chitosan films with zinc oxide (ZnO) nanoparticles that would retard the growth rate of bacteria and also be biodegradable? Chitosan films were cast with 0, 0.5, 1.0, 2.0 and 3.0 wt% ZnO, who’s mechanical, barrier and optical properties were measured, along with their action on three types of food pathogens, before being used to wrap fresh strawberries kept at 4 °C for 12 days. Loading of 1.0 wt% ZnO was optimal. Tensile strength increased by 24.5%, water vapour permeability decreased by 27% and UV transmittance at 280 nm reduced by 38% down to 11%, whereas still retaining transparency. The chitosan films reduced Escherichia coli, Staphylococcus aureus and Salmonella contamination by 4.1, 4.7 and 3.8 log units in 24 hours. The time to reach 20% degradation of strawberries covered by the film was about 10.5 days compared with 4.9 days of unpacked and 6.8 days of pure chitosan film-covered fruits. Nanoparticles formed aggregates at higher concentrations, limiting their content to 1.0 wt%. The process of making chitosan into an active packaging film requires only one step.