Cereal Chem 63:475-478   |  VIEW ARTICLE
New Chromophore for Phytic Acid Determination.

A. I. Mohamed, P. A. J. Perera, and Y. S. Hafez. Copyright 1986 by the American Association of Cereal Chemists, Inc. 

A direct spectrophotometric method was developed to analyze phytic acid without acid digestion. The method was based on the precipitation of phytate as ferric phytate followed by conversion to sodium phytate. On heating, phytate reacted with chromogenic reagent and a blue molybdenum complex was formed. The same reagent reacted with inorganic phosphate and produced a similar blue complex. Both these complexes had maximum absorption at 830 nm and were stable for several hours at room temperature. The color complexes obeyed Beer's Law over a wide range of concentrations of phytic acid and inorganic phosphate. The molar ratio of phosphorus to phytate was determined to be 5.84 by comparing moles of phosphorus in digested phytate to the moles of phytate in undigested phytate. The new chromophore was used to determine phytic acid in eight legume seeds. Values obtained for phytic acid with the new chromophore agreed with those obtained with Barlett reagent. Among the legumes investigated, soybean had the highest value (23.35 +/- 1.60 mg/g of meal), whereas black-eyed pea had the lowest (8.74 +/- 0.83 mg/g meal). The advantages of determining phytate from the new chromophore over methods in the literature are that it eliminates the need for acid digestion of phytate to inorganic phosphate; it is easy to prepare and is stable; the chromophore reacts with phytate over a wide range of pH from 1 to 13; and it can be used for monitoring chromatographic separation of inositol phosphates.