Functional properties of soy protein hydrolysates obtained by selective proteolysis

Soy protein hydrolysates were produced from a soy protein isolate (SPI) in which either the glycinin or β-conglycinin fractions had been selectively hydrolysed. The solubility, apparent viscosity, emulsifying activity, whippability and gel-forming ability of each hydrolysate were determined. Both hydrolysates had minimum solubility at around the same level of pH 4.5 as that of SPI. The reduced-β-conglycinin hydrolysate (RCH) showed lower apparent viscosity than the reduced-glycinin hydrolysate (RGH). Increased whippability was observed with both hydrolysates in comparison with SPI, whereas lower emulsifying activity was found, except at acidic pH 4. RCH retained more gel-forming ability than RGH when determined by mixing with salt-soluble meat protein. This result was supported by observation of the microstructure of the gels.