Multifunctional and washable supramolecular hydrogels constructed from co-assembly of tannic acid and stevioside for fruit preservation

Hydrogels derived from natural biomass are viewed as promising alternatives to petroleum-based fruit packaging due to the unique features of sustainable nature, biosafety, and environmental friendliness. However, biological macromolecules (e.g., polysaccharide and protein) generally lack antibacterial effect and UV shielding performance while existing hydrogels assembled from herbal small molecules (HSMs) are inadequate in mechanical properties, adhesion, and film-forming ability. To address this, we proposed a simple physical mixing method to construct supramolecular hydrogel based on tannic acid (TA) and stevioside (St) for fruit preservation. The monomers were proved to co-assemble into dense network structure driven by hydrogen bonding and π-π stacking interactions. Besides the good mechanical property, adhesion capability (87.55 kPa on polytetrafluoroethylene), and biocompatibility, the TA-St hydrogel exhibited excellent gas barrier (5.31 and 20.01 g/(m 2 ·h) for oxygen barrier and water vapor barrier, respectively), UV blocking performance (<350 nm), antioxidant activity (>86.66 %), and antibacterial ability (>99.99 %). Profiting from these comprehensive performances, the hydrogels were demonstrated to effectively reduce weight loss and maintain the fruit quality, significantly prolonging the shelf life to 12 days for blueberries. Notably, the TA-St hydrogel film possessing washability and biodegradability (5 days in soil) could be easily removed from the fruit surfaces. This work provides a new strategy to develop binary HSM-based supramolecular hydrogels with multifunctionality, boosting their applications in the fields of sustainable fruit preservation.