Removal of soy protein-bound phospholipids by a combination of sonication, β-cyclodextrin, and phospholipase A2 treatments.

One of the contributing factors to generation of off-flavours in soy protein isolate (SPI) during storage is autoxidation of residual amounts of phospholipids present in SPI. Thus, removal of phospholipids from SPI is a likely first step to improve its flavour stability and enhanced utilisation of SPI in food products. We describe a β-cyclodextrin-based (βCD) process to remove protein-bound phospholipids and free fatty acids in SPI. Treating SPI solution (8%) with 10mM βCD alone at pH 8.0 decreased the phospholipid content of SPI by about 36%. A greater than 99% removal of phospholipids and free fatty acids was achieved by using a combination of treatments involving sonication of the SPI solution for 5min at 50°C followed by treatment with phospholipase A2 and βCD. SPI prepared by this method was white in colour. The results presented here offer a process for removing residual off-flavour causing phospholipids from soy protein.