Studies On Producing Textured Soy Protein By Medium-sized Twin-screw Extruder

Textured soy protein (TSP) as a kind of plant protein which can be absorbed easily by the human body have so many wonderful characteristics such as high protein content, comprehensive nutrition, protein quality good. Textured soy protein will have higher protein content after deep processing. Textured soy protein have fiber structure just like muscle, which have a wide range of application in health foods, and have been widely used for meat products, dairy products, beverages, children's food, confectionery, fast food, frozen food and so on.Extrusion technology as a new processing method, its practical and economical characteristic, causes it widely used in the food industry. Using of the extrusion technology in food processing have the characteristics, includes simplier craft, lower consumption, more efficient and less investment. The products by extrusion have the values, containing feeling delicious, absorbing easily, and not easy to retrogradation. At present, Textured soy protein is mainly processed by extrusion.Soybean protein isolate was used to process textured soy protein in this experiment. The equipment we used in the experiment is a traditional twin-screw extruder which is mainly used to process puffed food. In order to process high quality textured soy protein, a reformative screw is designed for experiment according to the characteristics of textured soy protein. The result of this experiment shows that processing textured soy protein through reforming traditional extruder is feasible.The factors influencing extrusion effect in this experiment are moisture content, screw speed and extruding temperature. The range of these factors was found by single factor experiment. Regression equations for extruding criteria are established through three-factor with five-level quadratic regressive orthogonal rotatory experiments. The effects of moisture content, screw speed, extruding temperature on degree of swelling and shear force are discussed. By establishing a mathematical model, the influences of primary factors which affect the extruding criteria have been analyzed with curve surface function. By analysing the models, the order of factors importance is arranged. The order of the factors affecting the shear force is: the screw speed > the moisture content > the extruding temperature; and the order of the factors affecting the degree of swelling is: the extruding temperature > the moisture content > the screw speed.Finally, the technologic parameters have been optimized by the optimization theory. The optimum parameters are confirmed. The optimum parameters of shear force are: the moisture content 32%, the screw speed 80rpm, the extruding temperature 155℃, the theoretical value is 4.28, and the optimum parameters of the degree of swelling are: the moisture content 30%, the...