It has been reported that SPI shows great emulsifying properties. This is related to its high solubility and high protein content (Gwiazda et al., 1979).
Jideani (2011) write that SPI, as well as SPC, are good emulsifiers but that SPC shows lower emulsifying capacity than SPI. Environmental factors, such as pH, affect the emulsifying properties of soy protein and this was studied by McWatters and Cherry (1977). They saw that soybean flour was able to create a mayonnaise-like emulsion that was extremely thick (at pH 6.5 and pH 8.2). At lower pH values, a salad-like dressing emulsion was created.