Development of antibacterial ε-polylysine/chitosan hybrid films and the effect on citrus

In this study, the ε-polylysine (PL)/chitosan (CS) composite films with the PL concentration of 0%, 1%, 3%, 5% and 7% were prepared via casting method. The Fourier transform infrared (FTIR), scanning electron microscope (SEM), mechanical and antibacterial properties of PL/CS composite films, as well as the effect of PL/CS coatings on citrus were observed. FTIR spectra suggested that there was no strong hydrogen bond between CS and PL. SEM images indicated that the film surface was smooth and the addition of PL to chitosan lead to more holes. The tensile strength was deceasing and the elongation at break of the films was elevating with the increase of PL content. The antibacterial activity against Staphylococcus aureus and Escherichia coli of PL/CS composite films was enhanced with increasing of PL content. Furthermore, it was found that the PL/CS coatings inhibited efficiently the decline of total soluble solids (TSS), ascorbic acid content and reduced the disease incidence of citrus, compared with the control. Also the disease incidence of citrus was decreasing with the increase of PL content. However, the weight loss did not show significant differences between the coated citrus and control during the whole storage period.