Physicochemical and preservative properties of tyrosinase-crosslinked sodium caseinate-EGCG-carboxymethyl chitosan composite packaging: Comparison of blended and layer-by-layer films

Bio-based packaging materials reduce the interactions of foods with their environment, which improves their quality, safety, and shelf life. Simple blending and layer-by-layer (LBL) deposition methods are commonly used film preparation methods. However, it is not clear which method has a better preservation effect. In this study, differences in the structures and properties of tyrosinase-crosslinked sodium caseinate (SC)-epigallocatechin gallate (EGCG)-carboxymethyl chitosan (CMC) composite packaging materials (coatings and films) prepared by these two methods were compared. Fruit preservation experiments were carried out by applying blend or LBL coatings to banana or strawberry. The structural properties of films prepared by the blend and LBL methods were analyzed to provide insights into their different performances. The adsorption of the coating solution onto the fruit surfaces, as well as the microstructure and properties of the coatings formed, were the main factors affecting fruit preservation. Strawberry or banana coated by blend coatings exhibited a good appearance after 7 or 14 days. Overall, the water vapor barrier properties of the blend films were better than those of the LBL films. Moreover, the mechanical and EGCG-release properties of the blend films were also good. In summary, the properties of the coatings/films prepared by the blending and LBL methods were compared. This study helps to facilitate the rational design of edible packaging materials for different applications.