Inhomogeneous salt distribution in whey protein isolate-chitosan coacervates: Preparation, structure, formation...

This study determined the inhomogeneous salt distribution in whey protein isolate (WPI)-chitosan (CS) coacervates. It explored the relationships between preparation conditions, structure, and formation mechanism in the presence of sodium ions, and also studied the coacervates' diffusion and penetration in mucin. Varying salt concentrations, ratios, and pH levels led to different morphologies and salt partitions in sodium-containing WPI-CS coacervates. SEM and CLSM confirmed that sodium ions were adsorbed on WPI. Electrostatic interaction and hydrogen bonding drove the interaction between sodium-containing WPI-CS coacervates and mucin, with a stronger binding affinity at pH 6.0 as shown by QCM-D. Dynamic diffusion tests showed sodium-containing WPI-CS coacervates immobilized sodium ions, and sodium ions diffused faster in the turbid than in the phase-separated state. This research offers new insights for developing salt-reduced delivery carriers by examining sodium release among inhomogeneous salt distribution in coacervates.