Background: Soy protein isolate (SPI) can be used as an emulsifier to stabilize emulsions, though SPI is unstable under low acidic conditions. Stable composite particles of SPI and dextran sulfate (DS) can be formed by the electrostatic interaction at the pH 3.5. Furthermore, the SPI/DS composite particles can be used to prepare a high complex concentration emulsion. The stabilization properties of the high complex concentration emulsion were investigated.
Results: Compared to uncompounded SPI, the particle size of SPI/DS composite particles was smaller at 1.52 μm, and the absolute value of the potential increased to 19.9 mV when the mass ratio of SPI to DS was 1:1 and the pH was 3.5. With the DS ratio increased, the solubility of the composite particles increased to 14.44 times of the untreated protein at pH 3.5, while the surface hydrophobicity decreased. Electrostatic interactions and hydrogen bonds were the main forces between SPI and DS, and DS was electrostatically adsorbed on the surface of SPI. The emulsion stability significantly enhanced with the increase of complex concentration (38.88 times higher than at 1% concentration), the emulsion average droplet size was the lowest (9.64 μm), and the absolute value of potential was the highest (46.67 mV) when the mass ratio of SPI to DS was 1:1 and the complex concentration of 8%. The stability of the emulsion against freezing was improved.
Conclusion: The SPI/DS complex has high solubility and stability under low acidic conditions, and the emulsion of the SPI/DS complex has good stability. © 2023 Society of Chemical Industry.
Keywords: dextran sulfate; electrostatic interactions; high complex concentration emulsion; soy protein isolate.
© 2023 Society of Chemical Industry.