To get a thorough understanding of evolution of heat-induced gel in meat batters, water distribution, protein conformation and their chemical bonds at phase transition temperatures (20-74 °C) were investigated by Low-field NMR and FT-IR. Firstly, G' increased and tanδ decreased beyond 55 °C, when sol was completely changed into an elastic gel. Then water holding capacity (WHC) decreased along with decreasing relaxation time T22 and a new relaxation time T23 appeared at 50 °C, which indicated that partially immobilised water was converted into free water outside. Meanwhile, surface hydrophobicity increased significantly and free sulfhydryl contents decreased, which contributed to the formation of disulfide bonds, especially beyond 55 °C. Finally, the transformation of α-helix into β-sheets occurred, and increasing β-sheets are necessary for the formation of elastic gels. Moreover, there was a significant correlation between α-helical contents and water loss, surface hydrophobicity, sulfhydryl contents.
Keywords: Dynamic rheological property; Fourier transform infrared spectroscopy (FT-IR); Low-field nuclear magnetic resonance (Low-field NMR); Phase transition temperature; Protein structures; Water distribution.
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