Study On Textured Soy Protein Produced By High Moisture Extrusion Technology

China is the hometown of the soybean, also is the great nation of soybean food producing and expending. The soybean protein has the very high nutritional value. It's digestibility was between 84%~98%, and it was a major source of protein directly for the body, it's compositions of the amino acid balance basically except the methionine and the cystine to be slightly lower than the recommended value of FAO (the United Nations Food and Agriculture Organization), it is a complete protein.Extrusion cooking is an important textural reorganization technology of vegetable protein in food industry, which has the advantages such as low energy cost, high efficiency, and continuous process. The textured soy protein produced by extrusion is an important part of modern soy protein industry. Texturization processes via high moisture extrusion is a new development area in extrusion cooking. Products have the advantages such as uniform texture, high texturized degree, springiness, and nutritional value.In this paper, Soybean protein isolate(SPI), wheat gluten(WG) and low-temperature defatted soybean(LTDS) as the main raw material was used to produce high-moisture textured soy protein in accordance with the characteristics of textured soybean protein by SYSLG30-IV twin-screw extruder with cooling die. The processing of texturization of soybean protein was studyed with the method of testing. The scope of application of the processing parameters, material moisture, barrel temperature, screw speed, different protein content, were found out through the pre-test and single factor test at the regular production. The effect of the four factors of extruder on texture characteristics and product quality was studied through quadratic regressive orthogonal rotation design, and a mathematical model equation was established respectively. Stepwise regression analysis showed that with the increase of material moisture content, the texturized degree, springiness, moisture content of products increased, and the hardness and chewiness of products reduced; With the increase in barrel temperature, the texturized degree, hardness and gumminess of products increased,and moisture content of products decreased; With the increase of Screw speed, the extrudates'umminess increased, but little effect on other properties. With the change of different protein content, the chewiness, gumminess and color increased, and the hardness of products reduced. Material moisture and barrel temperature are the most important process parameters affecting the target parameters. By analysing the mathematical models of production sensory evaluation, the order of factors importance was arranged. The order of the factors affecting the degree of production quality was: material moisture >barrel temperature> screw speed> different protein content. With the sensory evaluation as target parameters, the optimum parameters were as follows: material moisture was 55%, barrel temperature was 150℃,screw speed was 208r/min, different protein content was SPI 34%, LTDS 31%, WG 35%. The texturization degree of production was 2.19, textured structure was obvious.Through observing microstructure of high moisture TSP product by SEM and analysising the effect of high moisture extrusion on urease activity,digestibility in vitro,nitrogen solubility index (NSI), results indicate that microstructure and properties of production were influenced by operating parameter. Fully high moisture TSP has obvious texturized structure with dense structure and springiness. The urease activity of TSP reduced significantly;protein digestibility in vitro increase 12.1% and the nitrogen solubility index of extrudate ranged from 6.5%～8.5%.