An intelligent and active polyvinyl alcohol hydrogel packaging incorporating alizarin and Zn-MOF for shrimp freshness monitoring and preservation

An intelligent and active hydrogel was developed by incorporating alizarin and a zinc-gallic acid metal-organic framework (Zn-MOF) into a polyvinyl alcohol matrix for simultaneous shrimp freshness monitoring and preservation. Zn-MOF imparted enhanced mechanical strength (1.3-fold tensile and 2.9-fold compressive modulus increases), greater amine gas adsorption (evidenced by an 11 rise in euclidean distance, ED), and strong antimicrobial and antioxidant activities, including 100 % antibacterial efficacy and radical scavenging rates of 81.09 %, 94.56 %, and 70.54 % for DPPH, ABTS, and OH radicals. The hydrogel showed a distinct yellow-to-purple transition across pH 6–12, serving as a visual indicator of shrimp spoilage, with ED values nonlinearly correlated with total volatile basic nitrogen (TVB-N) levels (R² = 0.9847). A smartphone-based portable device enabled rapid freshness evaluation via color changes. The hydrogel also reduced total viable count (TVC), TVB-N, and pH levels, extending shrimp shelf life by at least 3 days, demonstrating its industrial potential.