Pectin extraction from Opuntia dillenii and physicochemical characterization of the formed hydrogel

The paper aims to prepare antioxidant hydrogel from Opuntia dillenii, extract pectin by ultrasonic and ethanol precipitation, and form gel through the reaction between pectin with STPP (1%) and Ca (4%).At ultrasonic conditions of 37kHz, 70C, 120 min and the solvent to the raw material ratio of 10:1 (v/w) in an acidic environment (pH 2), the obtained pectin has a stable fibrous structure.70% ethanol allows the good precipitation of pectin, forming a hydrogel with a stable cross-linked polymer network.Physicochemical spectroscopy showed that FTIR shows -OH, -COOH, -COOR groups and cross-linking signs; SEM shows a homogeneous porous structure; XRD shows semi-crystalline properties; TGA records mass loss corresponding to dehydration and gradual decomposition; DSC shows phase transition peak, confirming the thermal stability of the system.These results showed that hydrogel has high antioxidant activity, opening up potential in biomedicine and food technology.