Inositol Phosphate Content of Some Cereal-Based Foods

Abstract

An HPLC method was used to quantify contents of inositol hexa-, penta-, tetra-, and triphosphate in various bread, breakfast cereal, pasta, and rye flour samples collected froom Finnish commercial mills and retail outlets. The highest contents in breakfast cereals (phytic acid over 10 μmol/g dry wt) were found in whole-meal porrige flakes, followed by müselies. Inositol hexa-, penta-, tetra-, and triphosphate levels in rice crispies and corn flakes were consistently low. Inositol hexaphosphate contents in pastas were about 5 μmol/g dry wt. The phytic acid contents in rye flours and whole-meal porrige flakes were on the same level and rye flours had only very low contents of inositol penta- and traces of inositol tetra- and triphosphates. The highest total inositol hexa-, penta-, tetra-, and triphosphate contents in breads were found in crispbreads, breads containing wheat and oat, and Finnish sourdough rye bread. Breads made predominantly of wheat had lower contents. Most of the inositol hexaphosphate in the various sourdough breads studied (rye breads, buckwheat, some domestic crispbreads, and a wheat and potato bread) had hydrolyzed, since the content of inositol hexaphosphate was low compared to that of inositol penta-, tetra-, and triphosphates. The average Finnish per capita intake of phytic acids from cereal products is roughly 370 mg/day. Dietary fiber is mainly supplied by cereal products, rye bread being the single most important source therein. Thus these foods were also assumed to be the most important sources of phytic acid. However, the share of rye bread (Finnish sourdough dark rye bread) is not a significant source of phytic acid. Cereal products, and rye bread in particular, are very important sources of inositol hexa-, penta, tetra-, and triphosphates.