Degradation of Phytate in Composite Wheat/cassava/sorghum Bread by Activation of Intrinsic Cereal Phytase

The objective of this study was to degrade the phytic acid content in composite wheat/cassava/ sorghum bread by activating intrinsic cereal phytases during the baking process.The aim was to reach a phytate:iron molar ratio <1 to achieve an enhanced iron absorption in humans.Means to activate the phytase included dough preparation at different pH values and temperature as well as pre-soaking of the sorghum flour before baking.The phytic acid and mineral content was measured by highperformance ion chromatography.In the composite bread without pH adjustment of the dough, the phytate content was 1.58 µmol/g.After adjustment of the dough pH to 4.3, the phytate content in the composite bread decreased to 0.86 µmol/g.Soaking of the sorghum flour at 22°C for 3 h at pH 4.3 before baking, further decreased the phytate content to 0.58 µmol/g.Increasing the soaking temperature to 37°C and addition of 10% wheat flour resulted in a phytate content of 0.14 µmol/g in the composite bread, that is a reduction by 97% of the initial phytate content.The phytate:iron molar ratio was then 0.70 and the phytate:zinc molar ratio was 1.1 that is expected to have a positive effect on the absorption of both minerals in humans.