Chitosan-coted food presering film surface modified by using DBD plasma technique for antimicrobial property improvement

Abstract

In order to improve the antimicrobial activity of food preserving films, the surfaces of four polymeric films (PVC, PE, PP, and PLA) were modified by dielectric barrier discharge (DBD) plasma before the chitosan coating to augment the interaction between the polymeric films and chitosan. The plasma-treated polymeric film samples were further immersed in a chitosan acetate solution with different concentrations of chitosan. The degree of deacetylation and the viscosity-average molecular weight of chitosan were 97% and 807 kDa, respectively. The optimum plasma treatment time was 10s as determined from contact angle measurements. The effect of the plasma treatment on the surface roughness was determined by atomic force microscopy (AFM). It was found that the surface roughness of all the plasma-treated films increased as compared to the plasma-untreated films. From the spectra of the X-ray photoelectron spectroscopy (XPS), the increments of polar functional groups, such as O=C-Oˑ and C-Oˑ, on the plasma-treated polymeric films were observed. It might be postulated that the DBD plasma enhanced the hydrophilicity of the polymeric films. The effects of chitosan concentration and washing cycles on the amount of coated chitosan on the polymeric films were investigated by the Kjaldahl method. The chitosan-coated polymeric films exhibited excellent antimicrobial activity against Escherichia coli and Staphylococcus aureus.