Effect of CaCl₂ on 2 heat-induced whey protein concentrate fibrillation pathways: Spontaneous and nuclear induction

Amyloid fibrils have many excellent functional properties that facilitate their applications in the food industry. There are 2 pathways for whey protein concentrate (WPC) to form amyloid fibril aggregates: spontaneous pathway and nuclear induction pathway. Low ionic strength is a necessary condition for the spontaneous pathway to proceed successfully. In this paper, the effect of salt ions on 2 WPC fibrillation pathways was investigated by adding CaCl₂. The results demonstrated WPC fibrils were unable to form normally through spontaneous pathway as adding CaCl₂; but still could form through nuclear induction pathway with 20 to 30 mM CaCl₂, the nuclei accelerated the fibrillation process led to the resistance to the disordered aggregation brought by CaCl₂. Moreover, divalent cations (Ca²⁺, Mg²⁺) had much stronger effects than monovalent cations (Na⁺) on fibril formation, and the results of X-ray photoelectron spectrum together with Fourier-transform infrared spectroscopy suggested that Ca²⁺ had a greater effect on the fibril formation than Cl^-.