pH-responsive carboxymethyl chitosan and sodium alginate hydrogel beads for the controlled release of a water-soluble turmeric extract with antioxidant activity

A pH-responsive carboxymethyl chitosan/sodium alginate (CMC/SA) composite bead was developed for a water-soluble antioxidant compound. Citric acid crosslinking promoted electrostatic interactions and hydrogen bonding between the polymers, allowing the incorporation of highly water-soluble antioxidant compounds. FTIR, SEM, and TGA analyses confirmed the formation and stability of the composite beads. Swelling studies showed that increasing CMC content influenced the pH-responsive behavior of the hydrogel, primarily through osmotic effects. Among the formulations, CMC/SA beads at a 0.5:1.0 ratio (S1) showed the most suitable characteristics for controlled release. Turmeric extract (5–20% v/v) was used as a model bioactive compound. Antioxidant activity (DPPH) increased with turmeric loading from 45.38% to 78.71%, while the encapsulation efficiency also increased from 31.94% to 37.33% over the same range. In vitro release studies showed pH-responsive behavior, with an initial burst release followed by sustained release. The formulation with the highest turmeric loading of 20% (v/v) (S8) achieved approximately 58% cumulative release at 10 h and 85% at 72 h. Higher turmeric loading improved antioxidant activity, encapsulation efficiency, and cumulative release, with the 20% (v/v) formulation showing the best overall performance among the tested systems. These findings indicate the potential of CMC/SA hydrogel beads for delivering highly water-soluble bioactive compounds, although further optimization is needed to improve encapsulation efficiency and release behavior for practical applications.