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 beta-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-beta-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. (C) 2004 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.