Preparation and characterization of edible films based on sodium alginate cross-linked lactoferrin-ergothioneine compounds: Unraveling molecular interactions

In this study, a novel protein-polysaccharide based edible film was developed by sodium alginate (SA) incorporating with lactoferrin (LF) and ergothioneine (EGT). A small quantity of LF (0.15% w/v) equipped edible films with excellent moisture protection performance caused by enhanced hydrophobicity, evidenced by the descending water vapor permeability and ascending water contact angle (rising from 38.1° to 74.1°). Meanwhile, the films exhibited strengthened tensile strength and declining moisture content because of the filling of LF. EGT was employed to improve the properties of films as well, which endowed the films with homogeneous microstructure and ultraviolet shielding ability. Notably, the films loaded with EGT witnessed a dramatic growth of DPPH (2,2-diphenyl-1-picrylhydrazyl) inhibition from 8.50% to 64.90% and remained antioxidant active during storage. In this context, the samples containing the EGT-LF complex showed superior physical properties and multiple functional activities against ultraviolet light, bacterium, and oxidation. The analysis aimed at the film-forming solutions and spectrum of films provided a better understanding of the structure of samples: The adhesion of LF on the SA network driven by electric interaction improved the crystallinity of films; whereas EGT reduced the surface charge of LF according to molecular docking model. Overall, these results indicated that LF-assisted SA might be utilized as a promising material for active packaging, while EGT could be adopted to modify the protein/polysaccharide compounds for improved functional features.