Ultrasound-assisted pH shift-induced interfacial remodeling for enhancing soluble yeast protein content: Effects on structure and interfacial properties of proteins under different treatment conditions

Solubility is a necessary condition for proteins to exert their functional properties. To expand the application of yeast protein (YP) in food production, the action of ultrasound-assisted pH shift on the solubility of YP was investigated. The solubility of YP increased significantly with ultrasound-assisted pH-shift treatment, especially the protein yield reached 83.82 ± 3.08% for the sample with an ultrasound power of 60% and an ultrasound time of 30 min (U60-pH12-30). In contrast, the yield and solubility of soluble YP showed less improvement with alkaline shift or ultrasound alone. Ultrasound-assisted pH shift treatment significantly increased the content of β-sheet, free sulfhydryl groups, and disulfide bonds, and the samples had a loose and disordered microstructure compared to the treatment alone. In addition, the combined treatment considerably minimized the particle size of the protein and increased the solubility, foaming properties, and surface hydrophobicity (H0) value, especially the H0 of U60-pH12-30, which showed the highest value (451.70 ± 25.66). In summary, ultrasound-assisted pH shift treatment could significantly enhance protein solubility, thereby increasing the amount of soluble protein and improving protein processing properties.