Core-shell structured alginate-based hydrogel beads modified by starch and protocatechuic acid: Preparation, characterization, phenolic slow release and stable antioxidant potential

A novel core-shell structured alginate-based hydrogel bead modified by co-gelatinizing with starch and protocatechuic acid (PA), was designed to modulate physical properties of beads, release behavior and antioxidant stability of encapsulated bioactives. Core was fabricated by ionotropic gelation, and its formulation (ratio of sodium alginate/starch) was determined by particle size/starch distribution, texture and bioactive encapsulation capacity of core. Then, coating core with shell-forming solution co-gelatinized with different doses of PA, and subsequently cross-linked with Ca2+ to obtain core-shell structured beads. Surface microstructure, mechanical characteristics, and swelling ratio of beads were affected by concentrations of PA. Besides, core-shell structure containing PA could enhance delivery and sustained release of encapsulated phenolic bioactives during in vitro digestion, and improve their antioxidant potential stability. Furthermore, interaction between PA and polysaccharide components was elucidated by FTIR and TGA. The present information was beneficial for the advancement of functional food materials and bioactive delivery systems.