The Study Of Fiber-Textrued Extrusion Technology On Vegetable Proteins

In this paper, SLG32-Ⅱtwin-screw extruder was used on the study of SPI (Soy Protein Isolates) .The effects of some extrusion materials (flour, modified starch, wheat protein and tofukasu) on the quality of TSP(texturized soy protein) were investigated, at first; the effects of extrusion parameters for processing on the quality of TSP were analyzed. Then the effects of pH value on the qualities and structures of TSP products were studied in detail, and the optimized way of extrusion parameters was found in alkali states. The mechanisms of the fibrous structures formation during extrusion cooking of SPI were analyzed and discussed. The main conclusions of above researches as follows:1 .To research the selection of textural materials, we studied the effect of flour, modified starch, wheat protein and tofukasu on the quality of TSP. Results indicate as follows: all materials in feed have significantly effects on the sensory qualities, rheological properties and functional properties of TSP products. Flour is the essential condition for SPI() can be texturized or not; Modified starch enhanced the smooth extent of TSP product; wheat protein did heavier contribution to adhesiveness and cohesiveness of product; and tofukasu promoted the fibrous structures of TSP product. In the test conditions, the addition of materials proportion examined 12% flour, 19% Modified starch, 10% wheat protein and 6% tofukasu.2.Extrusion temperature and moisture content of material have the most significant effects on the qualities of TSP products during the extrusion cooking of SPI, and the effects of screw speed are second. Extrusion temperature is the key parameter for SPI can be texturized or not. While the effects of moisture content is important condition for the texturized quality of TSP products. The role of screw speed is mainly about to the resident time of feed in the extruder, and therefore bring effects on the texturized structures and sensory qualities of TPP products. Furthermore, in the test conditions, the optimal extrusion parameters is 40%moisture content of material, 140℃extrusion temperature, ratio of module diameter 1: 10 and the screw speed at 250r/min.3.The research of extruded-condition at alkali environment showed that: pH value have significantly effects on the sensory qualities of TSP products. The chewiness of products would be higher with increasing the pH value; and the addition of konjac gum enhanced the meat-like fibrous of TSP products, however overdose konjac gum will lead to higher hardness of products. At last, the material conditions examined 15%modified starch, pH value 13, 0.05%konjac gum. And using orthogonal methodology to examined the extrusion parameters is 50%moisture content of material, 150℃extrusion temperature and the screw speed at 250r/min.4.The results of mechanisms study of the fibrous structures formation during extrusion cooking showed that: noncovalent bonds play important roles in the formation of fibrous structures during SPI extrusion cooking, and the effects of disulfide are the second, 7S globulin was destroyed severely during SPI extrusion cooking; disulfide bonds play important roles in the formation of fibrous structures during SPI extrusion cooking in alkali environment, and the effects of noncovalent bonds are the second, US globulin was destroyed heavily during SPI extrusion cooking. And that high molecular protein formed through hydrophobic interactions and intermolrcular disulfide bonds formation which was the main reason of forming meat-like fibrous products. Furthermore, meat-like fibrous products are more possible formed in alkali states.