Influence of sodium and calcium ions on rheological behaviour of wheat glutenins extracted in alkaline ethanol solution

Wheat glutenins were extracted in alkaline aqueous solution containing 50% (v/v) ethanol and 0.025  m NaOH from the gluten residue after extraction using 70% (v/v) aqueous ethanol. Rheological behaviours of the solutions were investigated as a function of protein concentration and ion strength. Sodium (Na⁺) and calcium (Ca²⁺) ions have different influences on the rheological behaviour of the glutenin solution of 48 mg mL^?1. While addition of Na⁺ results in Newtonian fluids with a reduction in apparent viscosity in comparison with the salt-free solution, addition of Ca²⁺ leads to the formation of a viscoelastic network with enhanced shear-thinning. The solutions containing 0.2  m and 0.4  m Ca²⁺ exhibit yielding at low strain rates. The solution containing 0.6  m Ca²⁺ behaves as a pseudoplastic fluid with the appearance of two Newtonian plateaus at low and high strain-rate limits.