Effect of nixtamalization with Ca(OH)2, CaCl2, and CaCO3 on the protein secondary structure, rheological, and textural properties of soft wheat flour doughs

The effect of dough formation using dynamic rheology, thixotropy, zeta-potential, and FT-IR properties of soft wheat dough as a function of Ca(OH)2, and Ca-salts contents (0.3%, 0.7%, and 1.1%) was investigated. Physical data were further supplemented by measurements of dough texture profile analysis, wet gluten, and pH. Additional information provided by structure-sensitive properties, such as the zeta-potential, thixotropic index, and slopes of rheo-destroyed and complex viscosity curves using Cox–Merz rule, can comprise complementary instances of evidence of the ability of dough self-regeneration or build-up after rheodestruction to certain limits. There is a different behavior of the dough properties above and below pH 7.0. Above pI ≈ 5.2, dough (pH 5.5–7.0) has zeta-potential with negative charge from ionizing hydroxyl groups of starch and proteins that favor protein unfolding and that increase α-helix, wet gluten, and functionality. Weak non-covalent bonds and electrostatic forces induce strong entanglement and interaction with water, increase swelling, and preserve the chemical structure. However, at pH > 7.0, Ca(OH)2 treatment changed to negative charge tendency of the dough system, specifically of starch. The effects provided by nixtamalization are essential for its application in improvement of wheat flour with limited functionality, such as soft wheat flour and other grains or materials.