Physical and Chemical Characteristics of Extruded Rice Flour and Rice Flour fortified with Soybean Protein Isolate

Texturized products were produced from rice flour and rice flour fortified with Soy Protein Isolate (SPI) by extrusion cooking. Water absorption capacity (WA) of the extrudates was slightly depressed in the presence of SPI. Scanning electron microscopy revealed that the file structure of the textured products differed subtly from each other and that SPI formed fine strings in the starch matrix. Solubility tests indicated that thermoplastic extrusion processing increased noncovalent interaction and disulfide bonding resulting in decreased protein solubility. 7S subunit of the soy protein seemed more affected than the 11s component. Insolubilization was significantly less when rice flour and SPI were processed simultaneously indicating a sparing effect in their mutual presence.