Self-assembly of amyloid-like nanofibrils during heating of bovine whey protein at 80 degrees C and pH 2 is accelerated by the presence of NaCl and/or CaCl(2), but the rheological consequences of accelerated self-assembly are largely unknown. This investigation focused on the impact of CaCl(2) on the evolution of rheological properties and fibril morphology of heated whey protein isolate (WPI), both during self-assembly at high temperature and after cooling. Continous rotational rheometry of heated 2% w/w WPI showed a nonlinear effect of CaCl(2) on the viscosity of fibril dispersions which we attributed to effects on fibril flexibility and thus the balance between intrafibril, entanglements. Small amplitude oscillatory measurements made in situ during heating of 10% w/w WPI at 80 degrees C suggest that CaCl(2) is not involved in either fibril structure or gel structure, and this was confirmed with dialysis experiments.