Abstract:

【Objective】 The effect of feed moisture content on quality of texturization of extruded soybean protein was investigated in order to provide a theoretical basis for producing of textured meat analogue by extrusion technology. 【Method】Soybean protein isolate (SPI) with moisture content at 28%-60% were processed using a DSE-25 pilot-scale twin-screw extruder. The protein solubility of both raw material and extrudates from various treatments were analyzed based on 8 different buffer solutions, which contained only phosphate (P); two reagents, i.e. sodium dodecyl sulfate (P+S), urea (P+U) and 2-mercaptoethanol (P+M); three reagents, i.e. (P+S+U), (P+U+M) and (P+M+S); four reagents, i.e. (P+S+U+M). The chemical cross-linkage of textured soybean protein was further analyzed based on the solubility. The distribution of molecular weight and degree of polymerization were investigated by using SDS-PAGE electrophoresis. The quality of texturization of extrudate from soybean protein was characterized by degree of texturization measurement and scanning electronic microscopy (SEM). 【Result】 With moisture content increasing, the solubility of extrudates in P decreased significantly (P＜0.05), the solubility in P+S+M and P+M+U increased dramatically (P＜0.05), the degree of forming macromolecule polymer decreased, the fibrous and porous structure in extrudate appeared, and the degree of texturization increased significantly. 【Conclusion】 Increasing moisture content could promote the alignment of soybean globulin, increase the interactions between disulfide bonds and hydrogen bond, disulfide bonds and hydrophobic bonds dramatically, decrease the degree of polymerization, further enhance the quality of texturization in extruded soybean protein.

Key words: moisture content, soybean protein, extrusion cooking, protein solubility, quality of texturization