Small-strain dynamic rheology of food protein networks.

Small-amplitude oscillatory shear analyses of samples containing protein are useful for determining the nature of the protein matrix without damaging it. G' (elastic or storage modulus), G'' (viscous or loss modulus), and tan δ (loss tangent, the ratio of G'' to G') give information on the properties of the network. Strain, frequency, time, and temperature sweeps provide information on the linear viscoelastic region, structural assembly, and thermal characteristics. The gelation point may be determined by locating the time at which tan δ is independent of frequency or the temperature at which G' becomes greater than G''. The logarithm of η* (complex viscosity) may be plotted against the reciprocal of the absolute temperature, with the slope being proportional to the activation energy. Dynamic tests of protein-containing samples reveal a great deal about their rheological characteristics.