Synergistic construction of low-temperature-resistant, water-retaining, and cushioning hydrogels via 1-s UV curing and ethylene glycol annealing for postharvest fruit protection.

Abstract

Hydrogels are promising cushioning materials for fresh produce packaging because of their viscoelasticity, deformability, and energy-dissipation capability. In this study, a UV-curable hydrogel based on methacrylated hyaluronic acid (HAMA) was developed. Through ethylene glycol (EG) annealing, a cushioning material (HAMA-EG) with good low-temperature tolerance and high water retention was fabricated. Systematic characterizations indicated that the hydrogel achieved rapid 1 s UV curing, attributed to approximately 0.69 methacryloyl groups grafted per HA disaccharide unit, which provided sufficient photosensitive crosslinking sites on the HAMA chains. HAMA-EG also exhibited a regular porous structure, good mechanical properties (Young's modulus of 0.28 MPa and compressive strength of 3.85 MPa), and biocompatibility. The incorporation of EG enhanced the material's low-temperature resistance (no freezing at -40 °C) and environmental stability (cumulative weight loss of only 29.41% after 120 h). In addition, HAMA-EG Gel showed enhanced cyclic mechanical stability after environmental pretreatment; after -20 °C freezing, its cyclic mechanical retention remained at 72.52%, compared with 6.43% for HAMA Gel. In simulated vibration and drop transportation tests using peaches as a bruise-sensitive fruit model, HAMA-EG reduced mechanical damage and better maintained fruit quality than commercial cushioning materials. Overall, HAMA-EG enabled rapid curing and forming with good energy dissipation and water-retention properties, thus holding broad application in cushioning protection for fresh produce.