Isostrength comparison of large-strain (fracture) rheological properties of egg white and whey protein gels

The effects of protein concentration and heating conditions on the physical properties of whey protein isolate (WPI) (in 50 mM NaCl, pH 7) and egg white (pH 9) gels were examined. Egg white and WPI gels had similar values for shear stress at fracture (i.e., isostrength), while trends for shear strain at fracture were protein-type specific. The rigidity ratio (R-0.3), ratio of the rigidity at fracture (G(f)) to the rigidity at 30% of fracture strain, measured departure from the stress-strain relationship of an ideal Hookean solid. All gels fit master curves of G(f) vs R-0.3, which were described by a power law model of R-0.3=A(G(f))(-0.19), where "A" showed protein type-specific characteristics.