Cinnamaldehyde-lactic acid deep eutectic solvent modified chitosan composite film and its application in grape preservation

Cinnamaldehyde-DL-lactic acid DES enhances chitosan film performance. • Covalent immobilization of cinnamaldehyde via Schiff base reaction. • Composite film exhibits UV-blocking, antifogging, and antibacterial activities. • The CS(CIN:LA)60 film effectively extends grape shelf-life. To address the issues of non-degradability in traditional petroleum-based packaging materials and the limitations of chitosan (CS) films (e.g., poor mechanical properties, insufficient water resistance, and single functionality), this study incorporated a deep eutectic solvent (DES) composed of cinnamaldehyde (CIN) and DL-lactic acid (LA) into the CS matrix to fabricate high-performance composite films. The effect of DES content on the structure and properties of the composite films was investigated. FTIR and XPS analyses suggested that a fraction of the aldehyde groups of CIN participated in Schiff base formation with the amino groups of CS. Together with hydrogen-bond reorganization and LA induced protonation of CS amino groups, these interactions contributed to the regulation of the CS network. When the DES content was 60% of the dry weight of CS, the resulting CS(CIN:LA)60 film exhibited the optimal comprehensive performance: its tensile strength (TS) reached as high as 41.57 MPa; the water contact angle (WCA) was approximately 100°, indicating good hydrophobicity; the water vapor transmission rate (WVTR) was reduced to 560.2 g/(m 2 ·24h); meanwhile, it possessed excellent ultraviolet (UV) shielding ability, remarkable anti-fogging performance, and good antibacterial activity. Grape preservation experiments demonstrated that the CS(CIN:LA)60 film could effectively inhibit microbial growth, reduce water loss, and delay fruit softening and the degradation of nutritional components. Compared with commercial polyethylene (PE) cling film, the composite film showed advantages in antibacterial activity, anti-fogging performance, and the maintenance of several grape quality attributes. This study provides a new strategy for the development of green food packaging materials. Download: Download high-res image (552KB) Download: Download full-size image