Application of modified chitosan/cellulose nanocrystals-stabilized Pickering emulsion active films for preservation...

Mango is a popular tropical fruit valued for its flavor and nutritional richness. However, its postharvest shelf life is limited because of its climacteric nature, which leads to rapid softening and spoilage. Chitosan-based coatings suffer from limited mechanical strength and single-function antimicrobial activity. To address these limitations, a bifunctional modified chitosan (MCS) was synthesized by grafting quaternary phosphonium salts and sorbic acid onto the chitosan backbone. This MCS was then combined with a thyme essential oil (TEO) Pickering emulsion stabilized by cellulose nanocrystals (CNC) to fabricate an active composite coating (MCS-PE). The chemical structure, thermal stability, mechanical properties, and barrier properties of the composite films were characterized. The results indicated that the composite film loading with TEO at 3 μL/mL exhibited favorable tensile strength (10.94 MPa) and elongation at break (41.12%). Antibacterial assays revealed that the MCS-PE film-forming solution had excellent activity against Escherichia coli, Staphylococcus aureus and C.gloeosporioides. The coating films effectively extended the storage life of mangoes at 25 °C, as indicated by assessments of peel color, firmness, weight loss, and other physiological indices. Consequently, mangoes coated with the optimal MCS-PE3 coating film (3 μL/mL TEO) had a shelf-life extension of at least 10 days compared to the uncoated control group. The sensory acceptability of the coated mangoes, particularly regarding potential flavor alteration, should be evaluated in future studies prior to commercial application. This work demonstrates that the synergistic integration of bifunctional chemical modification and Pickering emulsion stabilization offers a promising strategy for designing next-generation fruit preservation coatings.