Spinach is normally prepared by boiling and then immersion in cold water. Commercial frozen spinach, however, is labeled “use as-is.” If commercial frozen spinach has a high oxalic acid content, then there is a risk of greater intake of oxalic acid if it is eaten as-is. The aim of this study was to ascertain the amount of oxalic acid in commercial frozen spinach. Frozen spinach were purchased from three companies （A, B and C）. These samples were allowed to natural thawing or thawing in running water. The amount of oxalic acid per 1g of a sample （dry weight） was determined. The amount of oxalic acid when natural thawing in Sample A, B and C were 28.7mg⁄gDW, 32.6mg⁄gDW, 48.2mg⁄gDW, respectively. The amount of oxalic acid when thawed in running water in Sample A, B and C were 17.3mg⁄gDW , 24.6mg⁄gDW, 38.6mg⁄gDW, respectively. All three samples contained more oxalic acid when natural thawing than when thawed in running water, and Sample A and B contained significantly more oxalic acid when natural thawing than when thawed in running water （p<0.01）. In this study, it was confirmed that amount of oxalic acid can be reduced by thawing frozen spinach in running water.
