Characteristics Comparative Study on Two Extraction Types of Soy Protein Isolates

Defatted soy flakes were washed with aqueous alcohol and the resultant material was extracted with water to prepare soy protein isolate (SPI-A) with improved functional properties in comparing with the conventional soy protein isolate(SPI-C)extracted directly from the alkaline low-denatured soy flakes. Gelling property was determined by rheometer at the protein concentration of 12% (W/W) while the gel fracture force of SPI-A was 385.4g, substantially higher than that of SPI-C (85.4g). Emulsifying and foaming stability were also found to be improved through alcohol washing. High performance size exclusion chromatography showed that when SPI-A and SPI-C were both eluted around the same time, the laser light scattering analysis indicated that SPI-A solution contains particles with larger hydrodynamic radius than SPI-C, suggesting that SPI-A forms larger protein aggregates with more flexible structure whereas SPI-C forms smaller and more compacted aggregates.