Development and characterization of alginate/konjac glucomannan composite film reinforced with propolis extract and tea tree essential oil co-loaded Pickering emulsions for strawberry preservation

The development of multifunctional biodegradable films addressing sustainable food packaging demands requires innovative integration of active components and structural engineering. Herein, an eco-friendly sodium alginate (SA)/konjac glucomannan (KGM) composite film (SK film) with improved physicochemical properties and added functionality was prepared by incorporating propolis ethanol extract (PEE) and tea tree essential oil (TTO) co-loaded Pickering emulsions (PTEOs). PTEOs have excellent physical stability with an average particle size of 18.1 μm. By optimizing the emulsion-to-matrix ratio, the SK composite film incorporated with 2 % PTEOs (SK/PTEOs2) exhibited enhanced mechanical strength (tensile strength increased by ∼12.5 MPa) and barrier efficacy (water vapor permeability reduction reduced by ∼50 %, UV-blocking ability by ∼31.9 %) compared to pristine SK films. Moreover, SK/PTEOs2 composite film demonstrated potent antimicrobial activity against Escherichia coli and Staphylococcus aureus (inhibition zone diameter > 18 mm) and remarkable antioxidant capacity (DPPH/ABTS radical scavenging > 80 %). Structural characterization confirmed hydrogen bonding between the emulsion droplets and polymer matrix, enhancing film homogeneity. In strawberry preservation trials, SK/PTEOs2 film extended shelf life by 3–4 days at 25 ℃, preserved hardness (retention ≥ 91 %), limited total soluble solids (TSS < 7 % loss), and reduced quality loss by 14.2 % versus unpackaged controls. Soil burial tests revealed rapid biodegradability (60 % mass loss within 21 days), aligning with circular economy principles. These results demonstrated the inclusion of PTEOs into SK film was a promising technique and offers a great potential application as an active food packaging systems in the food industry.