Effects of Various Chlorides on the Softening of Cooked Japanese Radish Roots and on the Pectic Composition after Cooking

Abstract

Disks of Japanese radish r oots were cooked in various chloride solutions to investigate the effects of metallic chlorides on the softening of cooked vegetables. When cooked in several chloride solutions, the softening, amount of pectic substances released into the solutions, and amount of water-soluble pectin remaining in the tissues were (greatest to least) 0.2 M FeCl₃>NaCl>KCl>MgCl₂>distilled water>CaCl₂, AlCl₃and FeCl₂. There was a correlation between the softening of the disks and the pectic solubilization. This suggests that KCl, NaCl and MgCl₂ accelerated pectin solubilization, consequently affecting the softening of the vegetables. CaCl₂, AlCl₃ and FeCl₂ inhibited pectin solubilization, and hence made the cooked vegetables firmer. The disks cooked in an FeCl₃ solution were extremely soft, because of the hydrolysis of pectic substances by contamination with a strong acid (pH 0.9).
The pH values of the solutions after cooking were different according to the kind and concentration of chlorides. The pH value of the cooking solution also affected the softening of disks. There was a large difference between CaCl₂ and (CH₃COO)₂Ca on the softening of Japanese radish roots by cooking. Comparing the pH value of the cooking solutions and the concentration of Ca²⁺, the pH value had a greater effect than the Ca²⁺ concentration.