Schiff base crosslinked soy protein/dialdehyde cellulose/jasmine residue extract films: Antioxidant, UV-shielding for fruit preservation

To address the limitations of petroleum-based plastic films and meet the growing demand for sustainable food packaging, a new biodegradable composite film was developed using soy protein isolate (SPI) as the matrix. The amino groups in SPI and the active aldehyde groups in water-soluble dialdehyde cellulose (S-DCF), extracted and modified from mulberry branches, were utilized to construct a three-dimensional network structure through a dynamic Schiff base reaction (-CH=N-). This cross-linking effect reduced the slippage of the protein molecular chain and improved the orderliness of the chain segments, increasing the tensile strength of the film by 154 %. Meanwhile, the polar groups introduced by aldehyde oxidation enhanced interfacial compatibility through hydrogen bonds, synergistically optimizing the water vapor barrier properties and forming a dual enhancement mechanism of “chemical cross-linking-physical entanglement.” Additionally, the flavonoids (JFE) extracted from jasmine residues synergistically achieved the dual functions of free radical scavenging (scavenging rate of 82 %) and UV shielding (transmittance in the 200–400 nm band <1 %) through the phenolic hydroxyl hydrogen donation-conjugated aromatic ring structure. Furthermore, the composite film demonstrated excellent biodegradability in soil and effectively delayed the water loss and decay of fruits such as persimmons and blueberries, realizing a positive “packaging-environment” cycle and confirming its potential as an active and sustainable packaging material.