Development of plastic/gelatin bilayer active packaging film with antibacterial and water-absorbing functions for lamb preservation

In order to extend the shelf life of refrigerating raw lamb by inhibiting the growth of microorganisms, preventing the oxidation of fat and protein, and absorbing the juice outflow of lamb during storage, an active packaging system based on plastic/gelatin bilayer film with essential oil was developed in this study. Three kinds of petroleum-derived plastic films, oriented polypropylene (OPP), polyethylene terephthalate (PET), and polyethylene (PE), were coated with gelatin to make bilayer films for lamb preservation. The results showed significant improvement in the mechanical properties, oxygen, moisture, and light barriers of the bilayer films compared to the gelatin film. The OPP/gelatin bilayer film was selected for further experiments because of its highest acceptance by panelists. If the amount of juice outflow was less than 350% of the mass of the gelatin layer, it was difficult for the gelatin film to separate from lamb. With the increase in essential oil concentration, the water absorption capacity decreased. The OPP/gelatin bilayer films with 20% mustard or 10% oregano essential oils inhibited the growth of bacteria in lamb and displayed better mechanical properties. Essential oil decreased the brightness and light transmittance of the bilayer films and made the film yellow. In conclusion, our results suggested that the active packaging system based on OPP/gelatin bilayer film was more suitable for raw lamb preservation than single-layer gelatin film or petroleum-derived plastic film, but need further study, including minimizing the amount of essential oil, enhancing the mechanical strength of the gelatin film after water absorption.