Rheology of Xanthan Gum Aqueous Solution

Xanthan Gum (XG) is a polysaccharide that is produced by the bacterium Xanthomonas campestris through fermentation, as discussed in Chap. 2 . The practical use of XG in various industries, including food processing, pharmaceuticals, cosmetics, agriculture, and engineering, is mainly a result of its ability to induce high viscosity at low polymer concentrations in aqueous environments. It can modify the rheological behavior of fluids (i.e., the flow and deformation of XG suspension under applied stresses) by acting as a thickener and stabilizer. For the former, XG is a highly effective thickening agent. It forms a network of long-chain polymers that entrap water and increase the viscosity of the fluid. As elaborated later, the thickening properties of XG are dependent on various factors, such as XG concentration, the solution pH and temperature, shear rate, and the presence of salts and/or other chemical additives. Moreover, the rheological behavior of XG solutions is pseudoplastic, which means that the viscosity decreases with increasing shear rate. Additionally, XG is an effective stabilizer, particularly in emulsions. It can stabilize oil-in-water emulsions by forming a protective layer around the oil droplets, preventing them from coalescing. XG can also stabilize suspensions by preventing settling and maintaining a uniform distribution of particles.