恒温冻藏对面筋蛋白结构及热力学特性的影响

Effect of the Duration of Frozen Storage on the Structure and Thermodynamic Properties of Gluten Protein

摘要:

本研究采用凝胶渗透色谱与光散射连用仪（SEC-MALLS）、扫描电子显微镜（SEM）和热重分析器（TGA）探讨了恒温冻藏（-18 ℃）过程中对小麦面筋蛋白分子量及其分布、微观结构与热力学特性的影响。实验发现，随着冻藏时间的增加，由于二硫键的断裂，自由巯基含量增加，面筋蛋白发生了解聚现象，产生了小分子量的蛋白质。分子量较高的面筋蛋白（分子量范围：106 u~4?108 u），在冻藏120 d后分子量下降，而分子量较低的面筋蛋白（分子量范围：105 u~106 u），在冻藏60 d后分子量就开始发生了明显的下降。冻藏后面筋蛋白的网络状结构明显疏松，冻藏120 d后有直径超过100 μm的孔洞的出现，且分布不均一。热分析结果表明，面筋蛋白与麦谷蛋白的裂解温度都随着冻藏时间的增加而呈现下降的趋势，热稳定性下降。说明，冻藏过程中在水分的迁移和重结晶的作用下导致面筋蛋白高聚物发生了解聚现象，造成了面筋蛋白分子间二硫键的断裂，从而使得其网络结构疏松，面筋蛋白与麦谷蛋白热稳定性下降。

Abstract:

The effects of frozen storage (-18 ℃) on the molecular weight, the distribution of molecular weight, microstructure and thermodynamic properties of wheat gluten protein were studied by size-exclusion chromatography in conjunction with multi-angle laser light scattering (SEC-MALLS), scanning electron microscope (SEM) and thermogravimetric analyzer (TGA). With increasing storage time, free thiol content increased due to the cleavage of disulfide bonds. Depolymerisation of the gluten proteins occurred, and low molecular weight proteins were produced. The molecular weight of the gluten proteins with relatively high molecular weight (106 u ~ 4 ? 108 u) was decreased after 120 days of storage, and that of the relatively low molecular weight (105 u ~ 106 u) gluten proteins exhibited a significant decline after 60 days of storage. The mesh like structure of gluten proteins became significantly loose, and unevenly distributed pores with a diameter over 100 μm could be seen after 120 days of storage. Thermal analysis indicated that the degradation temperatures of the gluten and glutenin showed a downward trend with increasing storage time and their thermal stability decreased. To summarize, during frozen storage, moisture migration and recrystallization led to the depolymerization of the gluten polymers, and the disulfide bonds between gluten protein molecules were broken, so that the mesh like structure became loose and the thermal stability of the gluten and glutenin decreased.