Efficiency of chitosan-based edible films loaded with nano-emulsion essential oils against coagulase positive Staphylococcus aureus isolated from chicken meat

Abstract

To decrease the incidence of coagulase positive Staphylococcus aureus (CPSA) in chicken meat, chitosan-based films incorporated with carvacrol nano-emulsion (Ch-CNE) and rosemary nano-emulsion (Ch-RNE) were used as an ideal solution to build effective antibacterial food packaging. CPSA was isolated from fresh and frozen chicken meat by using selective media. The prepared nano-emulsions were characterised using a zeta-sizer, Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and investigated for anti-CPSA activity by the agar diffusion method. The filmogenic mixture was prepared at 0.78% and 1.56% concentrations and then cast, dried, and assessed for physical and mechanical properties. CPSA was isolated from fresh and frozen chicken meat in percentages of 40% and 12%, respectively. The droplet sizes of the CNE and RNE were 54.56 and 44.98 nm, respectively, whereas those by TEM were spherically shaped with average sizes of 40.33 and 48.78 nm and polydispersity indices (PDI) of 0.32 and 0.21, respectively. The minimum inhibitory concentrations of both nano-emulsions against CPSA were 0.78% and 1.56%. Incorporated nano-emulsions with chitosan-based films did not cause a great change in the film appearance and transparency except for Ch-CNE films at 1.56%, which was significantly different in comparison with the control, and enhanced the light barrier property. Additionally, it caused significantly improved changes to the film including physical (water resistance and water vapour permeabi­lity) and mechanical (tensile strength and elongation at break) properties and significantly eradicated the CPSA inoculated in chicken meat (6 log10 CFU/cm2) on the 4th day of refrigerated storage (4±1 °C) with good organoleptic properties for 12 days. The Ch-CNE at concentration 1.56% could be considered a promising antimicrobial food packaging material with considerable beneficial packaging properties, substantial inhibition of foodborne pathogen growth, and extension of food shelf life