Epigallocatechin gallate-loaded casein nanoparticles filled into κ-carrageenan/gelatin to develop sustained-release bioactive composite films for long-term preservation of strawberry

With the advancement of food preservation materials, biodegradable bio-based antimicrobial materials have garnered significant attention. In this study, epigallocatechin gallate (EGCG)-loaded casein nanoparticles were prepared and incorporated into carrageenan/gelatin to develop a biodegradable composite film with synergistic antibacterial and antioxidant properties for strawberry preservation. The results revealed that nanoparticles prepared at a 1:1 casein-to-EGCG ratio exhibited optimal stability, achieving 90.59 % encapsulation efficiency. Phenolic hydroxyl and amine groups in Casein@EGCG nanoparticles formed cross-links with carrageenan/gelatin molecules through hydrogen bonding interactions. The addition of nanoparticles significantly enhanced the mechanical strength (53.14 MPa), UVA and UVB blocking properties (76.57 % and 91.27 %), and antibacterial and antioxidant activities of the composite films. Furthermore, the excellent water vapor barrier properties facilitated retaining fruit moisture. The composite film provided a slow-release matrix for the release of EGCG. The antibacterial and antioxidant composite film not only significantly extended the shelf life (8d) of strawberries but also demonstrated biodegradability, contributing to the innovative development of environmentally friendly food preservation materials.