Effects Of Different Components Of Soybean Varieties To The Quality Of Plaster Tofu And The Establishment Of Soybean Grading Standards

In this paper,58 soybean varieties were cultivated from different provinces were chosen as raw materials, and the contents of soybean protein,fat,moisture,trypsin inhibitors,phtytic acid,total flavonoids,lipoxygenase,phosphorus, iron, calcium, the storage proteins[glycinin(11S) and β-conglycinin(7S) fractions] were detected and analyzed. Soybeans were made into tofu according to the certain processes with CaSO4 as a coagulant and tofu yield, water retention and texture characteristics were tested.The soybean compositions and tofu quality indexes were studied by correlation and regression analysis.Then screened the tofu quality indicators which had a greater impact on the quality characteristics. Soybeans were classified by cluster analysis of the main quality indicators.Classification results based on screening criteria soybean varieties. Screenedsoybean varieties suitable for processing tofu.And the special soybean varieties screening grading standards were established.The results were meaningful to improve soybean processing quality and important to choose soybean species, increase tofu yield, and improve tofu quality. The main results were as follows:(1)There were big differences of the protein, fat, moisture, trypsin inhibitors, phytic acid, total flavonoids, and lipoxygenase, phosphorus, iron, calcium and protein subunits of 7S and 11 S subunit component content in different soybean species.(2)The phytic acid and phosphorus of soybean were significantly positive correlation with the yield of wet basis of tofu.The protein and phytic acid of soybean were significant positive correlation with the yield of dry basis of tofu.The water retention of tofu had a significantly positive correlation with the protein and phytic acid content,and a significant negative correlation with the fat content.The hardness of tofu had a significantly negative correlation with the protein,fat,phytic acid and water content.The elasticity of tofu had a significantly negative correlation with the fat content,and a significant positive correlation with the iron content.The cohesiveness of tofu had a significantly positive correlation with the trypsin inhibitor content,and a significantly negative correlation with phytic acid content.The stalemate of tofu had a significant negative correlation with fat and water content.The chewing of tofu had a significant positive correlation with fat content.The resilience of tofu had a significantly positive correlation with protein content.(3)The 7S protein of soybean had a significantly negative correlation with the yield,elasticity and cohesiveness of tofu,and a significant negative correlation with the hardness and resilience of tofu.The 11 S protein of soybean had a significantly positive correlation with the yield of tofu,and a significant positive correlation with the hardness of tofu.The ratio of 11S/7S had a significantly positive correlation with the three indicators.(4)The yeld of tofu had a significant difference between the different soybean varieties except the water retention.The texture index of tofu were significant.Regression analysis showed that soy protein content, fat content, total flavonoid content, moisture content, phytic acid,iron content and tofu quality indicators had a close relationship with quality indicators of tofu,using relevant indicators with higher levels of soy, tofu prepared a comprehensive characteristics of a better quality.Soy protein fractions α ’, α, β, A3, AS and BS subunit had a close relationship with the quality indicators of tofu, soy protein associated with a higher content of components, the tofu is better overall quality characteristics.(5)Develop a variety of content in soybean tofu target range, initially identified the grading standards of tofu making soybean varieties:the content of soybean protein is higher than 42%, fat content is less than 18%, phytic acid content is between 17mg/g and 20mg/g, protein subunit 7S content is less than 20%, 11 S content is higher than 45%.