Quaternary ammonium chitosan-based film reinforced with antibacterial Pickering emulsion synergistically stabilised by shellac nanoparticles and ε-polylysine for fruit preservation

This study aims to construct an antibacterial Pickering emulsion using the synergistic effect between shellac nanoparticles (SNPs) and ε-polylysine (ε-PL) to functionalise quaternary ammonium chitosan (QAC) films and apply them for fruit preservation. Results demonstrate that adjusting the ε-PL content can effectively modulate the stability, viscoelasticity and antibacterial properties of Pickering emulsions. Notably, the S-50 % ε-PL Pickering emulsion exhibits superior stability and viscoelasticity under acidic conditions and thereby effectively inhibits the growth of Escherichia coli and Staphylococcus aureus . Furthermore, the reversible transformation from demulsification to re-emulsification of an S-50 % ε-PL emulsion can be achieved by adjusting the pH. The re-emulsified Pickering emulsion exhibits physicochemical properties and demonstrates antibacterial performance similar to those of the original emulsion, indicating its excellent structural and functional recoverability. Notably, the incorporation of the S-100 % ε-PL emulsion addresses the QAC film’s limitations in terms of barrier property, thermal stability and antibacterial activity. When compared with untreated and pure QAC films, the Pickering emulsion–modified QAC films considerably inhibit microbial contamination of cherries and strawberries and delay their quality deterioration, as evidenced by key indicators, such as weight loss, pH, firmness, vitamin C, titratable acidity and total soluble solids. This study offers a novel strategy for designing antimicrobial Pickering emulsions and multifunctional biobased films.