Rheology of pectin solutions containing montmorillonite nanoparticles

Commercial high and low-methoxy pectins were blended with seven different modified montmorillonite clays and the resulting solutions were characterized by dynamic and transient rheology utilizing Couette geometry. Pectin solutions without clay nanoparticles served as control. In all cases, montorillonite clay-pectin dispersions possessed altered rheological properties, with more highly hydrophilic nanoparticles imparting higher moduli and stress values, along with more highly shear thinning characteristics, while clays with a more hydrophobic modification imparted higher moduli and stress values to a lesser degree, and tended to cause a more Newtonian-like flow. These results are coupled with NMR relaxometry and -potential, providing a more compete picture of the properties of the pectin/montmorillonite dispersions. Particle size varied in the pectin/clay dispersions; however, the zeta potential was nearly invariant with and without clay, regardless of clay modification. T2 spin-spin relaxometry tests showed a trend in which the hydrophilic samples had shorter relaxation time than the hydrophobic samples.