Chitosan and pectin-based films and coatings with active components for application in antimicrobial food packaging

Abstract

This investigation was aimed to develop films and coatings based on natural biopolymers and active components, with physicochemical and functional properties for application in antimicrobial packaging. Biopolymer films were obtained from emulsions and dispersions by casting method. Coatings were formed by the application of emulsions on existing packaging. Synthesis of emulsions and dispersions were performed by combining biopolymers (chitosan-gelatin, pectin-gelatin) with lemongrass essential oil (LEO), Zn(CH3COO)2•2H2O, or ZnO, as active components. Fourier transform infrared (FTIR) spectra of the films showed that the addition of glycerol contributed to the forming of strong hydrogen bonds between glycerol and chitosan-gelatin or pectin-gelatin composites, facilitating the process of polymer branching, which is substantial for encapsulation. Thermal analyses revealed two characteristic processes occurring at 110 °C (water evaporation) and within 215–235 °C (degradation of polysaccharide and glycerol). Major weight losses were observed at 290 °C (chitosan-gelatin films) and 215 °C (pectin-gelatin films). The chitosan-gelatin films exhibited a lower degree of solubility (31–21%), and better mechanical properties comparing with the pectin-gelatin films. The chitosan-gelatin emulsions and dispersions exhibited a higher antibacterial effect in vitro against E. coli, B. subtilis, and S. aureus. In the case of the pectin-gelatin emulsions, the impact of LEO on the antibacterial activity was evident. The effects of biopolymer coatings on the development of microorganisms on fresh raspberries (Rubus idaeus L.) were performed in vivo during eight days of raspberry storage at refrigerator temperature. The tested coatings extended the shelf life of stored raspberries from four to eight days. The synergistic effect between LEO and ZnO or Zn-Ac was observed both in vivo and in vitro.