Egg white ovomucin gels: structured fluids with weak polyelectrolyte properties

Abstract

Ovomucin is a mucin-type heteropolymer responsible for the gel-like nature of egg white. As a natural gelling agent, there is a vast potential in the utilization of the gelling ability of ovomucin. The purpose of the study was to understand the gelling properties of ovomucin and determine its possible applications. Rheological measurements revealed that ovomucin formed a gel at room temperature upon rehydration with distilled water with similar properties to other mucin gels. The gels of 0.5%, 1% and 2% behaved as structured fluids with a gel-like behavior under small amplitude oscillatory shear conditions. Stress sweeps of 1% and 2% ovomucin revealed an apparent yield stress and zero shear viscosity plateau, while no apparent yield stress was observed in 0.5% ovomucin. In addition, 2% ovomucin gel showed a complete reformation of its structure after the stress sweep. The microstructure of the gel showed a fibrous network that was observed by scanning and transmission electron microscopy. The gel was highly sensitive to the addition of salt, showing properties of a negatively charged weak polyelectrolyte that swells in water and collapses in salt solutions. Zeta potential measurements of 0.1% ovomucin further confirmed the importance of electrostatic interactions in preventing the collapse of the gel, in which strong hydrophobic interactions exist.