Investigation of the Effect of NaCl Concentrations on the Formation of Amyloid Fibrils During the Cooking of Wheat Noodles

In our previous study, we observed that sodium chloride (NaCl) influences the formation of amyloid fibrils (AFs) by gluten in cooked wheat noodles. However, the underlying mechanisms of NaCl's effect on AF formation during the cooking process remain unclear. This study systematically investigates the impact of NaCl concentration (0-2.0%, <i>w</i>/<i>w</i>) and cooking time (0-7 min) on AF formation. ThT fluorescence and Congo red confirmed AF formation across all NaCl concentration levels. At low NaCl concentrations, Na⁺/Cl^- shielding reduced electrostatic repulsion, enabling ordered β-sheet stacking, yielding long fibrils (1193 nm) with high β-sheet content (41.5%), dense cross-β structures, and elevated hydrophobicity (H₀ = 9980). Stable zeta potential and gradual particle growth (376 to 1193 nm) supported controlled elongation. Conversely, high NaCl concentrations disrupted hydrogen bonding, forming shorter fibrils (820 nm) with reduced β-sheets (28.9%) and lower hydrophobicity (H₀ = 5923). Rapid ThT kinetics (<i>df/dt</i> = 77,535 FU/min) and SE-HPLC profiles suggest that elevated concentrations of NaCl inhibit AF formation while inducing the generation of amorphous aggregates. These findings clarify the balance between ionic shielding and hydrophobic interactions in AF assembly, offering strategies to optimize noodle texture. Future studies should address the digestibility and health implications of salt-modulated AFs for functional food applications.