Relevant Research Of Soybean Proteins And Fatty Acids Compositions Between The Seeds And Tofu

There are abundant resources of soybean varieties in our country, where asignificant difference between the contents of soybean. Under the same processingmethods of preparation of tofu, there are significant differences in the texturecharacteristics of tofu made from different varieties, which may be related to thedifferences of the contents of soybean components. In soybean protein content,11Sand7S fraction accounts for about80%, their difference directly affect thenutritional value and functional properties of soy protein, which influences thedevelopment and utilization value of soybean protein. Differences in the compositionand proportion of the fatty acids compositions, is one of the most important factorsdetermining soybean oil quality, directly related to the nutritional value and thehuman body absorption and utilization of soybean oil.Totally16soybean varieties were selected as test materials in this study,according to the processing methods of preparation of tofu. A systematic analysis ofsoybean protein compositions and contents in soybean seeds and tofu are taken bySDS-PAGE. And a systematic analysis of the fatty acids compositions and contentsin soybean seeds and tofu are taken by GC-FID. The relationship of soybean proteincompositions and soybean fatty acids compositions in soybean seeds and tofu areanalyzed by SPSS13.0, and the effects of soybean proteins and soybean fatty acidscompositions on texture characteristics of tofu are analyzed. Through the study, onthe one hand, to provide a scientific basis for the evaluation of soybean varieties,development and utilization and genetic breeding; on the other hand, to provide anew idea for the research and development of traditional food, for selecting thesoybean varieties to improving tofu quality.Main results as follow:(1) The significant differences are showed in soybean protein, water-solubleprotein and fat contents between varieties.(2) Protein subunits are the same in soybean seeds and tofu between varieties. Alot of peptide in the small molecular are appeared in the tofu at14.3KD, which isassociated with the denaturation and degradation of7S fraction. The contents of7Sfraction and its subunits have a significant difference, and11S fraction and its subunits are more stable. The subunits of7S are detected separately and a bit lower,the acid subunits of11S fraction are richer, but basic subunits are lower.(3) The major fatty acids compositions of tofu are consistent with the soybeanseeds among different varieties, which are C16:0, C18:0, C18:1, C18:2and C18:3.Among different varieties, the contents of C18:1and C18:3in soybean seeds and tofuhave a significant differences, and yet C18:2no significant difference (p﹤0.05).(4) The content of7S fraction,11S fraction and11S/7S in soybean seeds andtofu are showed weak correlation, which is associated with the denaturationtemperatures of7S fraction (71℃) and11S fraction (92℃). In soybean seeds, thecontent of7S fraction is significantly negatively correlated with11S (r=-0.704),11S/7S is significantly negatively correlated with7S(r=-0.989), and is significantlypositively correlated with11S(r=0.782).(5) The contents of major fatty acids in tofu and C18:2/C18:3are positivelycorrelated with those in soybean seeds respectively(r=0.756,0.728,0.950,0.456,0.831,0.795).In soybean seeds, the content of C18:0is significantly negatively correlated withC16:0(r=-0.591); the content of C18:1is significantly negatively correlated with C16:0(r=-0.682), is significantly positively correlated with C18:0(r=-0.589); the content ofC18:2is significantly negatively correlated with C18:0, C18:1(r=-0.510，-0.934); thecontent of C18:3is significantly negatively correlated with C18:0(r=-0.512) and C18:1(r=-0.823), is significantly positively correlated with C18:2(r=0.697); C18:2/C18:3issignificantly positively correlated with C18:1(r=0.644), is significantly negativelycorrelated with C18:2(r=-0.473) and C18:3(r=-0.959).In tofu, the content of C18:1is negatively correlated with C16:0(r=-0.470); thecontent of C18:2is significantly negatively correlated with C16:0(r=-0.604); thecontent of C18:3is significantly positively correlated with C16:0(r=0.701), issignificantly negatively correlated with C18:2(r=-0.589); C18:2/C18:3is significantlynegatively correlated with C16:0(r=-0.707)and C18:3(r=-0.972), is significantlypositively correlated with C18:2(r=0.573).(6) Soybean water-soluble protein content is significantly negatively correlatedwith hardness (r=-0.742), springiness (r=-0.658), cohesiveness (r=-0.572), resilience(r=-0.700) of tofu texture characteristics. In the seeds, the content of7S fraction insoybean is significantly negatively correlated with hardness (r=-0.736), springiness(r=-0.600), cohesiveness (r=-0.748), resilience (r=-0.581) of tofu texture characteristics.11S/7S is significantly positively correlated with hardness(r=-0.758),springiness (r=-0.523), cohesiveness (r=-0.675), is correlated with resilience(r=0.487). In tofu, the content of7S fraction is significantly positively correlatedwith cohesiveness (r=0.513), where α′subunit is significantly positively correlatedwith cohesiveness (r=0.542), β subunit is positively correlated with hardness(r=0.508), springiness (r=0.512), cohesiveness (r=0.452). The content of11S fractionin tofu is significantly positively correlated with springiness (r=0.561), cohesiveness(r=0.603), resilience(r=0.524).11S/7S is negatively correlated with cohesiveness(r=-0.466).(7) Soybean fat content is significantly negatively correlated with chewiness(r=-0.685), is significantly positively correlated with resilience (r=0.503). In soybeanseeds, the content of C16:0, C18:2and C18:3is significantly negatively correlated withchewiness (r=-0.545,-0.721,-0.668), and the content of C18:1and C18:2/C18:3issignificantly positively correlated with chewiness of tofu (r=0.803,0.557). In tofu,the content of C18:0is negatively correlated with hardness (r=-0.476), and thecontent of C18:1is significantly positively correlated with chewiness (r=0.749).