Interactions and rheology of guar gum–mucin mixtures

Abstract

This work studies the molecular interactions of guar gum, one of the major hydrocolloids, with mucin as to understand guar gum's behavior and functionality upon consumption. Guar gum, mucin, and their binary mixtures were studied at different pH values. The phase stability and particle size distributions were recorded over a pH range of 1–7, and at a range of guar gum to mucin ratios. Aggregations leading to phase separations are more pronounced at low pH, especially when mucin is involved. The effect of electrostatic repulsions on phase stability as function of pH is discussed. The shear viscosity of these systems is dominated by the presence of guar gum, with few, if any, apparent synergies with mucin. The image changes in extensional viscosity, where strong negative synergies are encountered when mucin co-exists with guar gum. Taking into account the intrinsic viscosity and existing thermodynamic data, these synergies are attributed to transient steric interactions. The different effect of mucin on the shear and extensional rheologies of guar gum are discussed on the basis of molecular interactions. The discussion highlights the potentially important implications in the behavior of these systems during oral and other processes. • The interactions between guar gum and mucin are studied. • Phase separations and particle sizes are mapped for a range of pH values. • Shear rheology is dominated by the presence of guar gum. • The presence of mucin strongly affects the extensional rheology of guar gum. • Synergies and antagonisms in rheology are attributed to intermolecular interactions.