Self-healing cellulose-based hydrogel smart packaging embedded with anthocyanin-immobilized metal–organic frameworks for food preservation and freshness monitoring

Abstract

Free anthocyanins are highly susceptible to environmental degradation, which limits their application in intelligent food-packaging materials. In this study, anthocyanins were immobilized onto UiO66-NH2 and further incorporated into a cellulose nanofiber/poly (vinyl alcohol)/borax matrix via a one-step method to fabricate a self-healing hydrogel for pork freshness monitoring. Microstructural and physicochemical analyses suggested the successful formation of Ant@UiO66-NH2, in which anthocyanin immobilization was mediated by hydrogen bonding, π-π interactions, and weak coordination, thereby facilitating its stable incorporation into the hydrogel network. UiO66-NH2 also improved anthocyanin stability, while the self-healing behavior mainly originated from dynamic borate-diol linkages and reversible intermolecular interactions. With increasing Ant@UiO66-NH2 content, the tensile strength of the hydrogel increased by up to 53.12% compared with the control, while cell viability remained above 98%, indicating good cytocompatibility. The resulting hydrogels exhibited distinct pH- and ammonia-responsive color changes. During pork storage at 20 °C, the optimized hydrogel extended shelf life by approximately 12 h relative to the control. Moreover, the ΔE value of CPBA@U200 showed strong correlations with pork pH, total volatile basic nitrogen, and total viable counts (R2 > 0.90). Combined with CIE color-space quantification, CPBA@U100 exhibited improved color discrimination compared with the unmodified CPBA hydrogel, allowing for continuous monitoring of pork freshness throughout storage. Overall, this study provides an effective strategy for constructing multifunctional smart hydrogels with integrated self-healing, stabilization, and freshness-sensing properties.