Alginate and Chitosan-Based Hydrogels: Effects on the Stability of Encapsulated Quercetin Under Multiple Stress...

In this study, hydrogel systems were investigated as protective carriers for quercetin (Que), a sensitive phytopharmaceutical. Matrix-type calcium alginate microparticles and capsule-type calcium alginate-chitosan microparticles were subjected to processing relevant stresses, including storage at -20°C to 25°C for up to 30 days, repeated freeze-thaw cycling, thermal treatment up to 100°C, ultrasonic irradiation (40-200 W), microwave exposure (50-300 W), and UV irradiation (254 and 365 nm) for up to 60 min. The antioxidant activity of encapsulated Que was quantified using EPR spectroscopy based on DPPH radical-scavenging activity. The results demonstrate that polysaccharide-based carrier design plays key roles in determining payload functional stability under stress. Higher alginate concentrations significantly improved Que protection during frozen storage and high-intensity ultrasonic treatment, while chitosan coating provided additional interfacial shield. The alginate-chitosan system showed markedly enhanced resistance to thermal treatment, repeated freeze-thaw cycles, and microwave irradiation. Under moderate storage conditions (4°C and 25°C) and UV exposure, both alginate matrices and alginate-chitosan capsules exhibited comparable stabilization performance. Overall, this study provides quantitative structure-function insights into the stress-dependent protective behavior of polysaccharides and highlights the potential of polysaccharide-based hydrogels for improving the stability of antioxidant compounds during processing and storage in the food and pharmaceutical industry.