Study On The Effects Of Twin-Screw Extrusion Expansion System On The Nutritional Quality Of Soybean Meal

Soybean meals which have a high protein content and a reasonable constitutional rate of the essential amino acids are widely used in food industry. And they have great differences in quality by different treated processes of soybean raw material. By the practice, it shows that the harmful ingredients effecting nutrient absorption in soybean could be removed by extrusion expansion which is a high temperature and high pressure treatment processing. Extrusion method that guarantees the low rate of residual oil while guarantees a low degree of protein denaturation has become the most important forage soybean processing methods.Five indexes were studied in this paper including NSI, WHC, crude fiber content, urease activity and phytic acid content in the meal after pretreating soybean with extrusion. Furthermore, four factors (nozzle diameter, material moisure, rotate speed of screw, temperature of barrel) were chosen to find the influence between indexes and factors. A mathematical model was established to discuss the influence law between indexes and factors, basing on a revolving, orthogonal and tropical design of the second power. The mathematical model that has been analyzed by SAS and optimized by GA of Matlab7.5 would be taken as the scientific bassis for industry. Specific research results are as follows.1. Various factors impacted on protein meal about the size of NSI are as follows: moisture content of material, rotational speed of screw, diameter of die nozzle, temperature of barrel. The optimal conditions extrusion of high NSI value whose parameters are that diameter of die nozzle is 10mm, moisture content of material is 10.4%, rotational speed of screw is 124 r?min-1, temperature of barrel is 60℃would be obtained.2. The extrusion parameters which obtains a higher water-holding capacity of Soybean meal are that diameter of die nozzle is 14.8mm, moisture content of material is 18%, rotational speed of screw is 106r?min-1, temperature of barrel is 91.5℃. Extrusion parameters impacted of water- holding capacity of the meal protein are as follow: moisture content of material, temperature of barrel, rotational speed of screw, diameter of die nozzle.3. Crude fiber content of soybean meal is reduced through reducing the diameter of die nozzle and the rotational speed of screw and improving the moisture content of material and the temperature of barrel. The extrusion parameters which obtains a lower crude fiber content of Soybean meal are that diameter of die nozzle is 10mm, moisture content of material is 10%, rotational speed of screw is 160 r?min-1, temperature of barrel is 120℃.4. There is significant impact on the urease activity by the interaction between the extrusion parameters. The extrusion parameters which obtains a lower urease activity that is almost inactivity are that diameter of die nozzle is 26mm, moisture content of material is 18%, rotational speed of screw is 160 r?min-1, temperature of barrel is 120℃.5. It is conducive to phytic acid molecules passivating through improving the diameter of die nozzle, the rotational speed of screw, the temperature of barrel and the appropriate moisture content of material. The extrusion parameters which obtains the lowest phytic acid content are that diameter of die nozzle is 26mm, moisture content of material is 14%, rotational speed of screw is 160 r?min-1, temperature of barrel is 106.5℃.6. Optimized by the fuzzy comprehensive evaluation method, the extrusion parameters which made a high nutritional quality of the soybean meal with hight NSI, low crude fiber content and low urease activity are that diameter of die nozzle is 19mm～21mm, moisture content of material is 16%～17%, rotational speed of screw is 76 r?min-1～107 r?min-1, temperature of barrel is 77℃～93℃.