Rheological investigation of soy protein hydrogels induced by Maillard-type reaction

Abstract

Rheological measurements were used to determine the power law relationship between gel elastic modulus and protein concentration (solid volume fraction) for soy protein hydrogels. The slope calculated from the log–log plot was used to determine gel fractal dimension. The validity of the prefactor in the power law relationship was also studied. Soy protein at 6.5–9.5% was gelled using monofunctional (glyceraldehyde) or bifunctional (glutaraldehyde) Maillard cross-linkers with or without salt. Gel fractal dimension did not vary with cross-linker type or concentration, while prefactor values increased with cross-linker concentration and when salt was used. The invariability of the fractal dimension is believed related to the absence of effect of the cross-linking agents on protein ionic repulsions, while prefactor value is believed inversely proportional to the number of inter-floc particle–particle interactions in the three-dimensional network and to floc size. The prefactor value was thus shown to increase as cross-linking degree increased and gel lacunarity decreased.