A facile fabrication method of sericin/chitosan film without additives for fruit coating

Abstract

Sericin (SS) serves as a natural adhesive, binding silk fibers within the silkworm cocoon and shielding them from environmental stresses. Commonly, SS-based films rely on additives to improve their physical properties. In this study, we developed an additive-free film composed of SS and chitosan (CS) in an ethanol environment, achieving enhanced tensile strength, elongation at break, and water retention and release capacity through structural modification of SS. The physicochemical properties of the film were comprehensively characterized using FTIR, SEM, and contact angle analyses. Additionally, its antioxidant, antibacterial, and hemocompatibility properties were systematically evaluated, demonstrating its potential for diverse biomedical and environmental applications. Results demonstrated that a film with a SS-to-CS ratio of 2 : 1 exhibited strong DPPH and hydrogen peroxide scavenging activities, induced only 2.07% hemolysis, and displayed moderate antibacterial effects against both Gram-negative (Escherichia coli, Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus, Bacillus subtilis) bacteria. Biocompatibility and safe use of the SS/CS film were tested on rabbit and human red blood cells. Furthermore, the film was applied for postharvest preservation of fruits, extending the shelf life of bananas up to 8 days and maintaining the freshness of tomatoes for up to 40 days compared to 12 days for untreated samples. These findings highlight the potential of SS/CS films for sustainable agricultural product preservation.