Impact of Drying Methods and pH-Shift + US Modification of Mung Bean Protein on the Stability of Pickering Emulsion

Abstract

This study evaluates the stability and structural characteristics of Pickering emulsion (PE) stabilized by mung bean flour (MBF), spray-dried mung bean protein (SD-MBP), freeze-dried mung bean protein (FD-MBP), and their pH₁₂-shift combined with ultrasonication (US) modified forms: modified spray-dried (MSD-MBP) and freeze-dried mung bean protein (MFD-MBP). PE stabilized with SD-MBP exhibited smaller droplet size (1.89 μm) and higher zeta potential (−22 mV) compared with FD-MBP PE (−20.16 mV). The PE stabilized with MSD-MBP displayed the smallest droplet size (1.33 μm), lowest creaming index, and a gel-like structure with superior elastic and viscous moduli showing drying followed by pH₁₂-shift + US modification of protein further enhanced the stability of PE. These Pickering emulsions (PEs) showed higher pH stability, particularly at acidic and neutral pH levels, due to its dense interfacial film. Microstructural analysis (CLSM) showed homogeneously packed and tightly adsorbed interfacial layer with lowest droplet aggregation in PE stabilized with MSD-MBP. The modification of protein also enhanced the thermal resistance of PE and followed the order as SD-MBP > MSD-MBP > MFD-MBP > FD-MBP > MBF. FTIR analysis revealed the difference in the intensity of amide peaks of PE stabilized by MBF and its proteins. The tribological analysis of PE stabilized with MSD-MBP represents the distinct static and kinetic regions, with reduced frictional resistance at higher shear rates, indicating effective lubrication. The synergistic approach of drying and pH₁₂-shift + US modification of mung protein significantly improved stability and reduced creaming in PE, and the MSD-PE highlighted its potential to develop robust PEs with enhanced functionality.