Viscometric behavior of high-methoxy and low-methoxy pectin solutions

The hydrodynamic behavior of high-methoxy (HM) and low-methoxy (LM) pectin solutions was examined by capillary viscometric analysis. The LM-pectin was produced from the HM-pectin by PME-deesterification. As a result of the viscometric analysis, the PME-deesterified LM-pectin showed quite different solution behavior from the HM-pectin. The LM-pectin had larger intrinsic viscosity ([η]) than HM-pectin when dissolved in 0.005 and 0.05 M concentrations of monovalent salts whereas HM-pectin had a higher value of [η] when dissolved in 0.2 M salt than LM-pectin. The concentration dependence of HM-pectin ηred values was fairly constant, whereas the concentration dependence of LM-pectin ηred values had a tendency to decrease as the pectin concentration approached zero. The effect of salt-type on the hydrodynamic behavior of both HM- and LM-pectin solutions was almost negligible. The precipitous drop in LM-pectin [η] upon increasing the salt concentration from 0.05 to 0.2 M is interpreted as arising from its disaggregation. This interpretation is based in part on data from HPSEC with online light scattering and viscosity detection.