Rheological Properties of Gum Arabic Solution: the Effect of Arabinogalactan Protein Complex (AGP)

Gum arabic solution is generally regarded as a Newtonian liquid with an anomalous low viscosity. However, recent research on the rheological properties of gum arabic in water has shown that it is not simply Newtonian. In this work, rheological properties of gum arabic solutions were investigated, with emphasis on its non-Newtonian behaviour of shear thinning and thixotropy, and interpreted based on molecular association in the solution. It was found that the arabinogalactan protein complex (AGP) in gum arabic might be the main source of molecular association though it only represents about 10% of the total gum. The occurrence of AGP micelles endowed the gum arabic solution with non-Newtonian behaviour of shear thinning and thixotropy. This fact was evidenced by using single-walled carbon nanotubes (SWNTs) to trap AGP. The non-Newtonian behavior of gum arabic solution vanished after AGP was removed from the solution.