Abstract: To improve the mechanical properties, water-barrier capacity and functional activity of gelatin films, this study prepared composite active films by adding 0.625%, 1.25%, 1.875%, and 2.5% (V/V) curcumin-loaded emulsion (CE) stabilized by a covalent complex between β-lactoglobulin and β-glucan to gelatin solution. The microstructure, physicochemical properties, and functional activity of the films and their preservation effect on fresh-cut apples were systematically investigated. The results showed that CE was uniformly dispersed in the gelatin matrix through physical interactions such as hydrogen bonding, the film surface was smooth and dense, while the cross-section exhibited a porous network structure. With increasing CE addition, the thickness of the composite film increased, the color gradually changed from light yellow to dark yellow-brown, and the UV-visible light barrier property significantly enhanced; the mechanical properties initially increased and then decreased, and the composite film with 1.25% CE (G-CE-1.25) exhibited the best tensile strength (10.62 MPa) and elongation at break (31.56%). Compared with pure gelatin film, the moisture content, water solubility, and water vapor permeability of the composite films decreased by 26.5%, 28.3%, and 14.17%, respectively. Specificallys, both water solubility and moisture content reached their minimum values when the CE volume fraction was 2.5%, while water vapor permeability reached its lowest level when the CE volume fraction was 1.25%. The water contact angle increased from a maximum of 84.3° to 116.4°, indicating a shift from hydrophilicity to hydrophobicity. The antioxidant and antibacterial activities of the composite films significantly enhanced with increasing CE addition. The G-CE-1.25 film was the most effective in preserving the quality of fresh-cut apples. In summary, appropriate amounts of curcumin-loaded emulsion can synergistically improve the physicochemical properties and functional activity of gelatin films, and the G-CE-1.25 composite film shows good application potential as an active food packaging material.

Key words: β-lactoglobulin; β-glucan; covalent compound; curcumin-loaded emulsion; composite film; film properties