On Increase in Viscosity of Radish Root Pectin Solution by Adding NaCl and its Mechanism

Abstract

The effect of NaCl on relative viscosity of the pectin solution prepared from radish root pectin was studied. The results obtained were as follows: (1) Viscosity of the pectin solution was increased but its pH was decreased with the addition of NaCl. (2) The increase in viscosity of the pectin solution by added NaCl was proportional to the decrease in pH of the solution. (3) It was presumed that the addition of NaCl into the pectin solution caused the ion-exchange of H-ion of carboxyl group in pectin with Na-ion to form HCl which, by ionizing, decreased the pH of the pectin solution. (4) The inversely proportional change of viscosity to the pH change of the pectin solution was confirmed by measuring viscosity and pH of the solution which was diolyzed after the addition of NaCl to remove HCl produced, as well as of the solutions which containaed different amount of pectin with or without NaCl.