Structural and emulsifying properties of soy protein isolate subjected to acid and alkaline pH-shifting processes.
Structural unfolding of soy protein isolate (SPI) as induced by holding (0, 0.5, 1, 2, and 4 h) in acidic (pH 1.5-3.5) and alkaline (pH 10.0-12.0) pH solutions, followed by refolding (1 h) at pH 7.0, was analyzed. Changes in emulsifying properties of treated SPI were then examined. The pH-shifting treatments resulted in a substantial increase in protein surface hydrophobicity, intrinsic tryptophan fluorescence intensity, and disulfide-mediated aggregation, along with the exposure of tyrosine. After the pH-shifting processes, soy protein adopted a molten globule-like conformation that largely maintained the original secondary structure and overall compactness but lost some tertiary structure. These structural modifications, consequently, led to markedly improved emulsifying activity of SPI as well as the emulsion stability.
Jiang
Jiang
J
State Key Laboratory of Food Science and Technology and School of Food Science and Technology, Jiangnan University, Jiangsu, China.
Chen
Jie
J
Xiong
Youling L
YL
D000143:Acids / Q000737:chemistry; D000468:Alkalies / Q000737:chemistry; D004655:Emulsions / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D011487:Protein Conformation; D017510:Protein Folding; D055550:Protein Stability; D030262:Soybean Proteins / Q000737:chemistry* / Q000302:isolation & purification; D013499:Surface Properties
D000143:Acids; D000468:Alkalies; D004655:Emulsions; D030262:Soybean Proteins