Studies Of Evaluation Indicators And Correlation Of Extruded Soybean

Soybean is important food material and feed material for its abundant nutriments, but some antinutritional factors(ANFs) in soybean limit its application in food and feed industry. The extrusion process can reduce the side-effect of ANFs in soybean to human and animals because the content of ANFs decreases especially trypsin inhibitor while the content of nutrient remains unchanged. The quality indicators of extruded soybean are generally urease activity and protein solubility. In the process of production, only urease activity is detected, whether the urease activity can reflect the change of other ANFs in expanded soybean is still to be confirmed. This study aim to determine whether the urease activity as the key evaluation index in production is suitable through the research of the correlation between urease activity and other evaluation indexes of expanded soybean from different sources. The main contents and results of this study are as follows.(1) Determination of quality evaluation index and detection method of expanded soybean. The quality evaluation indexes of expanded soybean were determined by the analysis and are as follows: protein solubility degree(PS), urease activity(UA), trypsin inhibitor(TI) antigen protein(β-Conglycinin(β-Congly) and glycine(Gly)), oligosaccharide(Oligo)(raffinose(R) and stachyose(S)), soy isoflavones(SI) and soybean saponin(SS). At the same time, the detection methods of evaluation indexes were selected, and the extraction methods of Oligo, SI and SS were optimized.(2) By changing different process parameters, get the different aging degree of extruded soybean, research the change rule and correlation of evaluation index in different processing technology, and obtain the influencing factors of the change of evaluation index, the change with process parameters and the correlation between indicators. Compared with raw materials, PS, TI, β-Congly and Gly of extruded soybean have different degrees of significant decrease, the content of Oligo has no significant change, and the content of SI and SS are increased. Analyze the variation law between processing parameters and quality evaluation indexes, in the process of extrusion production, PS, TI and UA are most influenced by the conditioning temperature and show highly negative correlation with temperature, secondly, show significant positive correlation with the feeding speed. Antigen protein shows negative correlation with screw speed, and the structure of Gly is more stable than the β-Congly. The determining factor of the content increased of SI is the retention time. The determining factor of the content increased of SS is the conditioning temperature. When UA did not fall to 0, UA and the content of PS and TI have a high degree of correlation and can be used as an important indicator to judge the level of PS and TI. When UA fall to 0.3 U/g, β-Congly and Gly have significant decrease, but the float level is still large, this time through UA cannot completely determine the level of antigen protein(3) Collect the expanded soybean samples stably produced from famous expanded soybean enterprise, their working condition is relatively stable. Detect the quality evaluation indexes of the samples and carry on the correlation research. Compared with soybean raw materials, UA of expanded soybean is completely inactivated. PS, TI, β-Congly and Gly are significantly decreased and the average decrease is 17.69%, 67.37%, 88.31% and 51.78%. The contents of SI and SS are significantly increased and the average increase is 25.21% and 10.57%. The total content of Oligo has no significant change. TI, β-Congly and Gly are significantly decreased, but the float level is still large. In the process of production, using UA as the main quality evaluation index has a certain basis, but UA cannot complete response to the level of TI and antigen protein, PS also cannot complete response to the level of the two types of ANFs.(4) Collect the expanded soybean samples from different expanded soybean production enterprise in different regions of China and analyze, it can be concluded that PS, TI and antigen protein have different degrees of decrease and the float level is large when UA is completely inactivated. The change of evaluation index is basically the same as the change of the product of the famous expanded soybean enterprise, and the change range is determined by the structure of the different indexes.According to the above results we can figure out that in the process of production, using UA as the main quality evaluation index has a certain basis, but UA could not be used as a criterion for the judgment of TI and antigen protein. In this study, the reference range of each evaluation index of extruded soybean is obtained, and the reference range of PS, UA, TI, β-Congly and Gly of commercial samples is 70%~85%, 0~0.01 U/g, 10~30 mg/g, 7~40 mg/g and 20~80 mg/g. It is suggested that PS and Gly should be detected in the production of high quality expanded soybean. In this paper, a complete evaluation of expanded soybean was carried out through different aging degree of extruded soybean determine the extruded soybean quality evaluation index, and the reference range of the main quality evaluation index of extruded soybean is obtained and can provide a certain reference value for the production enterprise.