Alcohol Evaporation-Induced Coordinated Shrinkage of Chitosan-Based Composite Films for the Preservation of Perishable Foods

Abstract

The growing issue of food waste caused by spoilage has heightened the demand for sustainable food packaging. Chitosan-based composite films are promising due to their antibacterial activity and biodegradability, yet their industrial application is limited by insufficient mechanical strength, water resistance, and processability. Here, we report a simple alcohol evaporation-induced shrinkage strategy, particularly using methanol, which triggers coordinated shrinkage of chitosan-based composite films through intermolecular hydrogen bond strengthening among chitosan chains accompanied by water release. With methanol assistance, the films’ tensile strength approximately doubled, reaching 32.80 MPa, and their Young’s modulus increased to 630.31 MPa. After immersion in distilled water for 52 days, the films remained in a solid form and did not undergo complete dissolution. When applied to fresh fruits, the optimized films significantly extended the shelf life of avocados to 11 days and bananas to 6 days under ambient conditions (25 ± 2 °C, 60 ± 5% RH), highlighting their promise as high-performance, environmentally sustainable packaging materials. As a result, chitosan-based composite films demonstrated simultaneous improvements in mechanical strength and water resistance through a simple alcohol evaporation-induced shrinkage strategy, thereby extending the shelf life of perishable foods. This work establishes a generalizable approach for upgrading biodegradable composite films toward sustainable preservation of perishable foods.