Determination of viscosity and critical concentrations of commercial low methoxyl pectin

Abstract Determining viscosity and critical concentrations is essential for industrial application of pectin solution. Critical concentration can be determined rheologically based on zero shear viscosity , apparent viscosity, specific viscosity, and consistency index of dilute polymer solution. Direct experimental comparison of the aforementioned methods for critical concentration determination is still lacking. Therefore, this study aims to experimentally compare different viscosity methods to determine critical concentration of three different pectin solutions (sun flower, citrus, and apple). The three pectin sources at concentrations of 0.1–3.0 % (w/v) showed Newtonian to shear thinning behavior. The critical concentration ranges of pectin, from the lowest to highest, was sunflower (0.6792−0.9589 % (w/v)), citrus (0.7172−1.0347 % (w/v)), and apple (0.7645−1.1233 % (w/v)). Critical concentration determined based on consistency index was relatively close to the result obtained from zero shear viscosity. Whereas critical concentrations of the pectin solutions determined from specific viscosity and apparent viscosity were significantly different from critical concentration determined from zero shear viscosity.