Stabilization of anthocyanins in xanthan-based systems for synergistic cryogels with enhanced physicochemical and biological properties for visual freshness monitoring of Prussian carp (Carassius gibelio)

Ultra-light, physically and double cross-linked xanthan gum (Xn)-based cryogels incorporating anthocyanin-rich bilberry (BLB) extract were fabricated by cryogelation to act as multifunctional materials for real-time monitoring of Prussian carp spoilage. The BLB extract demonstrated a rich phytochemical profile (803 mg gallic acid equivalents/100 g fresh weight (FW), 291 mg catechin equivalents/100 g FW, and 377 mg cyanidin-3-glucoside/100 g FW) and a high antioxidant activity (EC 50 = 46.16 μg/mL). The cryogels displayed high porosity (98–99 %), with pore size and wall thickness modulated by the incorporated BLB content. The combined effect of chemical cross-linking and bioactive additive incorporation synergistically enhanced network density, achieving encapsulation efficiencies up to 39.27 % and demonstrating >90 % DPPH inhibition. Antimicrobial assays revealed remarkable activity (up to 100 %) of BLB-loaded Xn cryogels against Salmonella typhimurium , Escherichia coli , and Listeria monocytogenes . An increase in BLB concentration and cross-linking density resulted in an enhancement in the compressive strength of the cryogels, rising from 247 kPa to 498 kPa at 83 % strain, while reducing the water vapor sorption capacity. Anthocyanin stability was maintained up to 50 days under storage conditions. Chemically cross-linked, BLB-loaded Xn cryogels demonstrated rapid and reversible pH-sensitive color transitions during four consecutive cycles of exposure to ammonia and acetic acid. A visible color shift from purple to blue, corresponded to pH changes was observed during Carassius gibelio spoilage. These findings highlight the potential of BLB-loaded Xn cryogels as antioxidant, antimicrobial and intelligent freshness sensors for smart food packaging. • Dual cross-linked strategies to stabilize anthocyanins within xanthan-based cryogels. • Impact of drying procedure on porosity, gel fraction yield, and network stability. • Hybrid cryogels with remarkable antioxidant activity and antimicrobial efficacy. • Ultra-light hybrid cryogels endowed with improved ammonia sensitivity. • Real-time detection of Prussian carp freshness by visual color changes of indicators.