Elucidating the gas cell stabilization mechanism of buckwheat-wheat steamed bread induced by transglutaminase: A focus on the foaming and air-water interfacial properties of dough liquor

This work investigated the improvement mechanism of transglutaminase (TG) on the buckwheat-wheat steamed bread qualities from the view of protein structural, foaming and air-water interfacial properties of dough liquor (DL). TG reduced the hardness, ameliorated the crumb structure and enhanced the specific volume of buckwheat-wheat steamed bread by up to 9.0%. The DL yield, protein and water recovery were notably increased as the TG concentration increased to 0.2 U/g, then decreased with the higher TG concentrations. The low TG concentrations (<0.2 U/g) increased the protein molecular weight, and decreased the protein hydrophobicity, free amino and sulfhydryl groups content of DL. The high TG concentrations (>0.2 U/g) tended to induce both protein intermolecular and intramolecular cross-linking, which reduced the average particle size from 9.6 to 4.3 μm as the TG concentration increased from 0.2 to 1.0 U/g. TG markedly improved the foaming capacity and foam stability, decreased the surface tension and strengthened the interfacial films by enhancing the viscoelasticity modulus of buckwheat-wheat DL interfacial protein films. The topography of the air-water interfacial layer revealed that the TG-induced protein cross-linking led to a more homogeneous and denser topographical structure. This work will provide fresh insight into the effects of TG-induced protein cross-linking on gas cell stabilization and relate them to the buckwheat-wheat steamed bread quality properties.