The Potential of Fermentation and Contamination of Teff by Soil to Influence Iron Intake and Bioavailability from Injera Flatbread.

Abstract

The high phytic acid (PA) concentration in the diet based on teff injera is a likely contributing cause of iron deficiency in Ethiopia. We monitored PA during teff injera fermentation in 30 households in Debre Zeyit, Ethiopia and evaluated its influence on iron bioavailability, considering contaminant soil iron in teff flour. After fermentation (48h), mean PA concentration in injera batter decreased from 0.87 to 0.58 g/100 g dm (P < 0.001). Low phytase activity in teff flour (0.44 μmol phosphate/min/g) and a rapid drop in pH, indicated that PA degradation was driven by microbial phytases. The iron concentration in injera batter among the households ranged widely from 14.5-160.4 mg/100 g dm (mean: 34.7 mg/100 g dm) principally due to contamination with soil. Estimated intrinsic iron concentration of teff based on the strong correlation between total iron and aluminium concentrations (P < 0.001; aluminium concentrations in injera batter: 28.7-184.9 mg/100 g dm) was 4.4 mg/100 g dm, indicating that 86-97 % is extrinsic iron from soil. The median daily iron intakes from 3-day weighed food records in 10 young children were 18.9 mg/day including soil iron vs. 4.9 mg/day without soil iron (P < 0.01). The PA:iron molar ratios indicated low iron bioavailability from teff injera, particularly when soil iron was excluded. Traditional fermentation thus has a modest influence on PA levels and more complete degradation is needed to improve iron bioavailability. There is an urgent need to better understand the bioavailability of contamination iron from soil before considering national fortification or biofortification strategies in Ethiopia.