English

Lã­Dia Vilanculos Serafina,Svanberg Ulf

doi:10.5897/ajfs2020.2008

Abstract

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 in order 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 prior tobefore baking. The phytic acid and mineral content was measured by high high-performance 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 prior tobefore 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. Key words: Phytic acid, wheat flour, cassava flour, sorghum flour, bread making, soaking, pH.

Highlights

Bread has become the most widely consumed nonindigenous food product within Mozambique
The incorporation of 25% whole sorghum flour in the composite flour mixture resulted in a higher phytate content (5.26 μmol/g) as well as iron (12.1 μg/g) and zinc content (8.4 μg/g), compared with the corresponding values of 3.3 μmol/g, 7.7 μg/g, and 4.7 μg/g in the wheat flour
The phytate content of the wheat flour and the cassava flour was at the same level as that reported by Lazarte et al (2015) as well as the iron content of the cassava flour

Summary

Introduction

Bread has become the most widely consumed nonindigenous food product within Mozambique. Wheat flour, the most suitable cereal flour for bread making, is produced in less than 3% of the needs (FAOstat, 2018) and substantial quantities must be imported at a high cost (Akubor and Badifu, 2004). Replacing wheat flour with locally produced cereal and root-tuber flours would help to reduce the need for expensive wheat imports and promote the agriculture sector in Mozambique. Wholemeal cereal flours provide significant amounts of nutrients such as carbohydrate, protein, vitamin, minerals including the trace elements, and contain high levels of phytic acid (myo-inositolhexakisphosphate, InsP6) that inhibits the bioavailability of essential minerals such as iron and zinc (Hallberg et al, 1989; Nävert et al, 1985).

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Conclusion