Regulation of pH-responsive behavior in electrospun (copper sodium chlorophyllin-alizarin)/fish skin gelatin nanofiber-based hydrogel membranes and their application in real-time intelligent monitoring of fresh shrimp freshness

Fresh shrimp, a protein-rich aquatic product, is prone to microbial spoilage during storage and transportation, posing risks to human health. Since spoilage degree cannot be identified by the naked eye, responsive smart packaging is urgently needed for real-time freshness monitoring of fresh shrimp. Herein, pH-responsive (copper sodium chlorophyllin-alizarin)/fish skin gelatin nanofiber-based hydrogel membranes were fabricated by embedding copper sodium chlorophyllin (CSC) and alizarin (ALI) in fish skin gelatin (FSG) substrate via electrospinning technology, followed by crosslinking via Maillard reaction and subsequent hydrogel formation through water absorption-swelling mechanism. Their structure, physical properties, pH-responsive behavior and application in fresh shrimp packaging were systematically investigated. The FAC-3 hydrogel membranes, embedded with 0.294 wt% CSC-ALI, exhibited a well-defined three-dimensional porous structure and a swelling rate of 434.93 ± 18.83%. The FAC-3 displayed distinct color changes under varying pH conditions, along with excellent sensitivity and color reversibility upon exposure to ammonia/acetic acid vapors. Comprehensive evaluations of the sensory quality, pH value, packaging membrane color changes, total colony count and total volatile basic nitrogen (TVB-N) of fresh shrimp demonstrated that FAC-3 exhibited outstanding indicative and monitoring performance for refrigerated shrimp. This work offers new insights for the development of aquatic product freshness-indicating packaging.