Emulsifying properties of O/W emulsion stabilized by soy protein isolate and γ‐polyglutamic acid electrostatic complex
Bei Zhang, Lei Qi, Xinhua Xie, Yue Shen, Jiahui Li, Bobo Zhang, Hongshuai Zhu- Food Science
Abstract
In order to improve the emulsifying properties of soy protein around isoelectric point, soy protein isolate (SPI) and γ‐polyglutamic acid (γ‐PGA) complexes were prepared by electrostatic interaction. The formation of SPI–γ‐PGA electrostatic complex and emulsifying properties were investigated by monitoring turbidity, zeta potential, intrinsic fluorophores, emulsion characterization, and microstructure observation. The results showed that the formation of SPI–γ‐PGA electrostatic complex was identified through turbidimetric analysis and zeta‐potential measurement. Intrinsic fluorescence spectrum indicated internal structure changes of electrostatic complexes. Furthermore, SPI–γ‐PGA complex–stabilized emulsions showed better stability with small droplet sizes and slow growth as well as the uniform microstructure around the isoelectric point (pH 4.0–5.0) than SPI‐formed emulsions. Under the different thermal treatments and ionic strengths, emulsions stabilized by SPI–γ‐PGA‐soluble complex resulted in improved emulsion stability to environmental stresses. This may be attributed to the increased steric repulsion and electrostatic repulsion by SPI–γ‐PGA complexes at oil–water interfaces. The findings derived from this research would provide theoretical reference about SPI–γ‐PGA electrostatic complex that can be applied in acid beverages and developed a novel plant‐based sustainable stabilizer for emulsions.
Practical Application
The electrostatic interaction between SPI and γ‐PGA improved the emulsifying characteristics of soy protein around isoelectric point. The results derived from this research would expand applications of SPI–γ‐PGA‐soluble electrostatic complex that can be applied in acid beverages, as well as a novel plant‐based sustainable stabilizer for emulsions.