Ultrasonic combined pH shifting strategy for improving the stability of emulsion stabilized by yeast proteins: Focused on solubility, protein structure, interface properties.

In this study, the improvement mechanism of yeast proteins (YPs) with the ultrasonic and pH shifting treatment on the emulsion stability was investigated through the solubility, protein structure and interface behavior of YPs. Compared with only pH shifting or ultrasound treatment, the solubility of YPs with the combined treatment of ultrasonic and pH shifting was increased significantly. The soluble protein content of pH-U400 reached 85.51 %. The results of YPs structure demonstrated that the β-sheet, α-helix and disulfide bonds contents of YPs with the combined treatment first declined and subsequently increased with increasing ultrasonic power, under alkaline conditions. The fluorescence intensity and surface hydrophobicity first increased and then declined. The more flexible protein structure endowed pH-U400 with lower interfacial tension, higher interfacial diffusion, penetration and reorganization rate, and interfacial protein concentration. The pH-U400 showed the best emulsifying properties (emulsifying activity index was 27.05 m/g, emulsifying stability index was 31.27 min) and could prepare smaller and more uniform emulsion droplet. The results of multiple light scattering demonstrated that emulsion stabilized by pH-U400 showed the best stability. These results revealed the stability mechanism of emulsions stabilized by YPs and provided guidance for further development of practical YPs products in the food industry.