Study On Texturization Properties Of Soybean Protein By Extrusion

Soy protein is a complete plant protein and has a high nutritional value. At present, there were two kinds of soy protein products on the market. Soy protein powder products and textured soybean protein products. But the traditional textured soybean protein product was not instant and need reprocessing. The instant products which can eat directly rarely exist. In this study, the optimal extrusion parameters (revolution speed, extrusion temperature, moisture content and starch content)were optimized by the orthogonal experiment design through sensory evaluation, to get a kind of instant soybean protein food with high expansion and good taste by extrusion. And the properties of the extruded product were studied.The optimal extrusion parameters were obtained by the orthogonal experiment design through sensory evaluation, The results of extrusion parameters suggested that:moisture content15%, revolution speed of extruder120rpm,160℃of extrusion temperature. The characteristic parameters of the extruded product under the optimal extrusion process were: hardness4.3N/cm2; brittleness-23.9mm/cm2; expansion rate329%. Adding starch to the soy protein could improve the taste. The optimal extrusion parameters were obtained by the orthogonal experiment design through sensory evaluation, The results of extrusion parameters suggested that:moisture content20%, revolution speed of extruder130rpm,160℃of extrusion temperature, starch content10%. The characteristic parameters of the extruded product under the optimal extrusion process were:hardness4.9N/cm2; brittleness-21.8mm/cm2; expansion rate370%.In addition, density, water absorption index and water solubility indices, nitrogen dissolved index and emulsification and foaming of extruded soy protein product were also studied. The results indicated that the higher the moisture content, the greater the density of the sample, revolution speed and extrusion temperature did not have significant effect on the density. Add starch could reduce the density of the sample; moisture content of material, revolution speed and extrusion temperature did not have significant effect on the water-absorption index of the product, but they had significant effects on the water-solubility index. After add the starch, the water-absorption index of the product increased and water-solubility index decreased; The nitrogen dissolved index decreased with moisture content increased, and the nitrogen dissolved index was increased after the first drop trend with revolution speed from100r/min to140r/min and extrusion temperature from140℃to180℃. The nitrogen dissolved index decreased after add the starch; The emulsification, emulsion stability and foam stability of soy protein increased and foaming decreased by extrusion. After add the starch, the emulsification.emulsion stability and the foaming, foam stability were all increased, but the change were not significant.Scanning electron microscope (SEM) showed extruded soy protein product was uniform. The results of differential scanning calorimetry (DSC) indicated that it had thermal stability, too. SDS-PAGE showed that no sopeptide bond was formed, but some protein may be not combining by disulfide bond and polymerization into big molecules which could not be dissolving by reducing agent by other chemical bonds.