Fabrication of pH-responsive whey protein/sodium alginate composite hydrogel beads for theaflavins

In this study, pH-responsive whey protein (WP)/sodium alginate (SA) composite hydrogel beads using the ionic gelation method were described and evaluated for their potential as delivery carriers for theaflavin (TF). Fourier transform infrared spectroscopy (FTIR) confirmed the interaction between WP and SA in the hydrogel beads is driven primarily by the strong intermolecular interactions, including hydrogen bonding and electrostatic attractions. The swelling ratio of the beads possesses good pH dependence and pH reversibility, effectively preventing the release of TF in the gastric environment. The encapsulation efficiency (EE) of TF in hydrogel beads ranged from 94.995 +/- 0.03 to 95.709 +/- 0.14, with a loading capacity (LC) of 27-34 mg/g. In in vitro digestion simulations, owing to the pH responsiveness, hydrogel beads released minimal TF throughout gastric digestion and were fully released in the intestine phase. Additionally, the release kinetics of TF from the beads were further examined in a simulated intestinal environment. These findings suggest that the hydrogel bead system is a promising carrier for encapsulating TF, offering a theoretical and experimental basis for its future application in the food industry.