Innovative application of the pomegranate peel anthocyanins embedded within agar aerogels for real-time monitoring of shrimp freshness

The growing demand for real-time food quality monitoring has driven interest in sustainable, bio-based intelligent packaging systems. This study reports the development of a novel halochromic aerogel platform fabricated from agar and functionalized with pomegranate peel anthocyanins (PPA) for non-destructive freshness monitoring of shrimp. PPA extracted from Punica granatum peel exhibited high total anthocyanin content (250.43 ± 5.56 mg/g). Agar aerogels were prepared via an ethanol-induced sol-gel process followed by freeze-drying, and PPA was incorporated at 1.5% (w/w) under controlled pH and temperature to ensure pigment stability. Structural characterization revealed that PPA incorporation increased specific surface area (13.20 m²/g) and porosity while reducing average pore diameter (6.12 nm), as confirmed by BET and SEM analyses. Rheological assessments showed concentration-dependent viscoelasticity, with higher agar content enhancing mechanical strength but reducing flexibility. FTIR spectroscopy confirmed physical interactions between agar and anthocyanins, preserving the pH-responsive functionality of the pigment. XRD analysis indicated that PPA disrupted the crystalline domains of agar, leading to a more amorphous matrix. The aerogels exhibited a distinct pH-dependent color transition from red to purple and blue upon exposure to ammonia vapor, correlating strongly with shrimp spoilage parameters including TVB-N content (increased from 7.91 to 12.11 mg/100 g over 6 days), pH rise (5.79 to 6.39), and total viable count (2.10 to 3.94 log CFU/g). These findings demonstrate that agar-PPA aerogels offer a promising, environmentally friendly platform for real-time, visual seafood spoilage monitoring, combining tunable porosity, and chromogenic sensitivity. This approach valorizes agricultural by-products into smart packaging for perishable foods.