Facile Fabrication of Starch–Zein Core–Shell Microparticles by Antisolvent Precipitation for Reducing Starch Digestibility

This study aimed to slow down starch digestion by encapsulating the starch granule within a firm zein shell via solvent-exchange-induced zein deposition. The zein shell adhered tightly to the granule surface and the shell thickness increased with increasing zein concentration. The average shell thickness of microparticles produced with zein (1%, 2%, and 3% <i>w</i>/<i>v</i>) was 0.54 μm, 0.97 μm, and 1.63 μm, respectively. Thicker zein shells acted as a mechanical barrier limiting heat transfer and water penetration, thus significantly affecting the starch digestibility. The in vitro simulated digestion experiment indicated that CS-3% zein microparticles exhibited an approximately 19-fold higher resistant starch (RS) content compared with native corn starch. These findings demonstrated the potential of the zein acting as a shell material in developing delivery system for controlled starch digestion. Additionally, this study validated antisolvent precipitation as an effective method to construct hydrophilic core/hydrophobic shell delivery systems to encapsulate unstable and hygroscopic compounds.