小麦A、B淀粉凝胶质构特性与分子结构的关系

Relationship Between Texture Properties and Molecular Structure of A,B-Type Wheat Starch

利用凝胶质构分析技术对小麦A、B型淀粉的凝胶质构特性进行了研究,结果显示,B型淀粉凝胶较A型淀粉表现出较高的弹性和较强的内聚性,小麦全淀粉凝胶的弹性和内聚性主要受B型淀粉的影响。为了揭示小麦A、B型淀粉分子结构与其凝胶质构特性的关系,通过凝胶渗透色谱-多角度激光光散射技术和旋转流变技术,对小麦A、B型淀粉的分子量分布、构象以及分子的支叉结构进行了测定。研究结果表明A型淀粉重均分子量、数均分子量均大于B型淀粉,但B型淀粉分子量分布更广。并通过对小麦A、B型淀粉的均方根旋转半径和分子量之间的关系进行拟合,分别得到了二者的分子构像。结果显示,A型淀粉分子构象为棒状,有利于分子紧密排列,使A型淀粉凝胶硬度较大,B型淀粉分子构象为无规则卷曲状,且分子中含有较多的支叉结构使凝胶更易形成网状结构,使凝胶的弹性及内聚性增强。

The gel texture properties of wheat A-,B-type starch were investigated by using TA-XT2i texture analyzer.The results show that the B-type starch gel has higher springiness and cohesiveness than that of A-type starch gel,and the springiness and cohesiveness of the whole wheat starch is mainly influenced by B-type starch.In order to reveal the relationship between molecular structure and gel texture properties of A-,B-type wheat starch,the molecular weight distribution and the conformation and structure of A-and B-type wheat starch were investigated by method of gel permeation chromatography coupled with multiangle light scattering（GPC-MALS） and method of rotary rheology.The results show that the weight-average molecular mass（Mw） and number-average molecular mass（Mn） of A-type starch are both larger than that of B-type starch,and B-type starch has broader molecular weight distribution.Furthermore,the molecular conformations of A-and B-type were obtained by the slopes of the curves of log Rg-log Mw.It was found that the molecular conformation of B-type starch is random coil-like and has more branch structure,which tends to form network structure and causes the B-type starch to have a higher springiness and cohesiveness.