Transparent, Anti-Drying, Stretchable and Antibacterial Gelatin/Glycerol/NaCl Hydrogel for Strawberry Preservation

Hydrogel films, as emerging bio-based packaging materials, hold considerable promise for preserving perishable fruits such as strawberries. However, their application is limited by poor water retention, insufficient mechanical strength, and lack of antibacterial activity. In this study, gelatin was mixed with NaCl and then soaked in a glycerol/water binary solvent system to fabricate gelatin/glycerol/NaCl (GGN) hydrogels. Results showed that glycerol incorporation endowed the hydrogels with excellent anti-drying performance, attaining a residual mass ratio of 55% and a transmittance of 75% after 9 days. At 7.5% (w/w) NaCl, the hydrogel achieved a tensile strength of 110 kPa and an elongation at break of 250%, along with antibacterial rates of 75.60% against Staphylococcus aureus and 86.11% against Escherichia coli, respectively. Strawberry preservation tests demonstrated that the GGN hydrogel effectively reduced weight loss and maintained fruit quality over 8 days, outperforming the control and commercial PE film groups. Overall, this study presents a facile strategy for fabricating multifunctional gelatin-based hydrogel films, offering a viable alternative to petroleum-based plastics for perishable fruit preservation.