The optimum amount of water suitable for boiling spinach was evaluated by investigating changes in the color and tenderness, and the decrease in oxalic acid and potassium contents by increasing amounts of boiling water. The result of a sensory evaluation showed that the flavor and overall evaluation of the cooked spinach tended to decrease as the amount of boiling water was increased. There was no difference in the color tone, while the tenderness of the cooked spinach increased with increasing amount of boiling water. The oxalic acid content of spinach boiled in 5 times the amount of water decreased to about 61 % of the value for raw spinach harvested in the spring, and decreased to 45% of this value in 20 times the amount of boiling water. The change in potassium content was similar to that of the oxalic acid content. Although the content of free oxalic acid differed by 100 mg between 5 times and 20 times the amount of boiling water, there was no difference in the sensory evaluation. These results suggest that about 5 times the amount of boiling water is the optimum for boiling spinach.
