Synergistic ultrasound and pH-shifting treatment enhance the functionality of Chlorella protein: Modification in structure, interfacial and emulsifying properties

Chlorella protein can serve as an alternative protein source for humans, but its poor emulsifying properties limits its application in food systems. Ultrasound-assisted pH-shifting (pH 2 or 10) effectively enhanced the emulsifying properties of Chlorella protein. The combined alkaline pH 10 and ultrasound treatment increased the emulsifying activity index by 77.8% compared to the native protein. Multi-scale characterization revealed that the synergistic treatment induced protein structural loosening, enhanced molecular flexibility, and promoted exposure of hydrophobic and sulfhydryl groups. These structural changes facilitated rapid interfacial adsorption and the formation of a stable, viscoelastic interfacial film, ultimately yielding emulsions with finer droplets and improved stability. This study provides an effective physical modification strategy and theoretical foundation for developing Chlorella protein as a high-performance food emulsifier.