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