Interfacial shear rheology of interacting carbohydrate polyelectrolytes at the water–oil interface using an adapted conventional rheometer

Abstract

A conventional rheometer was adapted for carrying out interfacial shear measurements. The interfacial shear viscosity and the interfacial creep compliance-time properties of mesquite gum or mesquite gum–chitosan mixed films were determined at the water–mineral oil interface. The ratio of chitosan to mesquite gum, and aging time, influenced the interfacial shear viscosity and interfacial creep compliance-time properties of the films. Electrostatic coulombic interactions arose between the negatively charged mesquite gum and the positively charged chitosan molecules, and the strength of the interaction was influenced by the relative charge density between both biopolymers. The interfacial shear viscosity and the interfacial viscoelastic properties of films obtained from 10% (w/w) mesquite gum aqueous solutions were boosted by the addition of chitosan at concentrations of 0.2–0.6% (w/w), but depressed by addition of chitosan at concentrations of 0.8–1.0% (w/w).