Preparation and preservation performance study of chitosan-gelatin bilayer composite film with excellent mechanical properties and biodegradability.

Biomass-based materials typically exhibit strong hydrophilicity, resulting in films with suboptimal mechanical strength and preservation capacity. These limitations hinder their application in food packaging. Here, this work reports a biodegradable film with enhanced mechanical strength and antioxidant properties for food preservation. Chitosan was extracted from shrimp shells via alkali-based deacetylation and then combined with gelatin to prepare films using citric acid as a cross-linker. A double-layer composite film was fabricated by layer-by-layer casting, incorporating camellia oil into the antioxidant layer and Montmorillonite (MMT) into mechanical reinforcement layer, respectively. As a result, a multi-component collaborative design strategy (camellia oil-MMT-chitosan-gelatin) significantly enhances film performance. At a 1:1 mass ratio of MMT to chitosan, the composite film demonstrates a breaking strain of 386%, a water contact angle of 106.93°, and a DPPH radical scavenging efficiency of 99.85%. Used for fruit preservation, the chitosan-gelatin bilayer composite film extends the shelf life of strawberries from 3 to 11 days effectively compared with polyethylene films. Moreover, the used composite films degrade completely within 10 days in soil. In conclusion, this research not only enables the repurpose of biomass waste (e.g., shrimp and crab shells) but also develops a novel biodegradable active packaging material.