Phytic Acid Determination in Soybeans

Several established methods of phytic acid determination in soybeans were evaluated. Iron analysis methods, which rely on a 4:6 molar ratio of Fe:P, were eliminated because this ratio was not dependable. Three assay methods relying on phosphorus analysis were then compared. The anion‐exchange method was considered most accurate but not convenient for routine analysis. Analysis of the ferric phytate precipitate and a new method, analysis of the supernatant before and after ferric chloride precipitation, were judged against the anion‐exchange method under different extraction conditions. Based upon good agreement with anion‐exchange column results and acceptable reproducibility, the best methods were (1) precipitate analysis of phosphorus after extraction with 3% TCA + 10% sodium sulfate, or (2) the supernatant difference method after extraction with 1.2% HCl.