The effect of replacing electrolytic iron in a multi-micronutrient fortification mix with sodium iron(III) ethylenediaminetetraacetate (NaFeEDTA) on the sensory properties of porridge from maize meal

Abstract

In developing countries, iron deficiency (ID) and the related iron deficiency anaemia (IDA) affects about 50 % of children and woman and about 25 % of men. In total, an estimated two billion people is affected worldwide. In developing countries, a typical diet is based on cereals, legumes and vegetables and these contain many iron inhibitors like phytic acid and polyphenols. Iron fortification of maize meal, a staple food in South Africa is regarded as a cost effective, sustainable way to improve iron status in that country. The replacement of electrolytic iron with sodium iron (III) ethylenediaminetetraacetate (NaFeEDTA) (a more bioavailable source of iron) in the current multi-micronutrient fortificant premix added to maize meal as an iron fortificant compound has the potential to greatly enhance the efforts to improve the iron status of populations consuming high-phytate cereal-based diets. However, poor consumer acceptance, unacceptable taste and discolouration of iron fortified foods have been frequently listed as causes of unsuccessful iron fortification programmes. This study evaluated the effects of replacing electrolytic iron (35 mg iron/kg maize meal) in a multi-micronutrient fortificant premix with NaFeEDTA (at 15 and 30 mg iron/kg maize meal) added to special maize meal on the colour (L* a* b*) and sensory properties (appearance and flavour) of stiff porridges. The porridges were prepared using three different types of cooking vessels (stainless steel, cast iron and aluminium pots) and was evaluated fresh (within 30 minutes of preparation) and after 24 hour refrigerated storage (3 - 5 oC). The porridges were subjected to analytical sensory evaluation to test for difference or similarity and a consumer acceptance test (n = 80 consumers). Electrolytic iron significantly reduced L* and a* colour values in fortified maize meal when compared to maize meal fortified with the multi-micronutrient mix excluding iron. Elemental iron powders (e.g. electrolytic iron) being black or dark grey powders may have caused slight darkening of cereal flours. The spot iron test showed a uniform distribution of iron in maize meal with NaFeEDTA 15 (fortified with 15 mg iron/kg maize meal), NaFeEDTA 30 (fortified at 30 mg iron/kg maize meal) and electrolytic iron as well commercially fortified maize meals. Electrolytic iron or NaFeEDTA 15 and 30 maize meals resulted in stiff maize porridge prepared in aluminium, cast iron and stainless steel having lower L* values when compared to porridge prepared from maize meal fortified with the multi-micronutrient premix excluding iron. This could be attributed to interaction between polyphenols (ferulic and p-coumaric acid) found in maize meal and iron ions (Fe2+/Fe3+). This interaction has been suggested to induce structural changes and polymerisation in the polyphenols and thereby influencing their light absorption pattern and thus leading to darkening of maize porridges. Cast iron cookware showed significant differences (p < 0.05) between iron treated porridges and control porridge (fortified with premix excluding iron) in both appearance and flavour while stainless steel showed significant differences (p < 0.05) between iron treated porridges and control porridge only in flavour and aluminium cookware showed significant differences (p < 0.05) between iron treated porridges and control porridge only in appearance. These differences could be attributed to the differences in thermal conductivity and heat transfer of the materials of the different cooking vessels and possible leaching of iron ions (Fe3+/Fe2+) from cast iron and stainless steel cookware and aluminium (Al3+) ions from aluminium cookware at different concentrations and/or rates during the cooking process. Appearance changes are probably due to the interaction between ion irons and polyphenols while flavour changes could be attributed to possible lipid oxidation of linoleic acid, a major polyunsaturated fatty acid found in maize meal. Iron ions (Fe3+/Fe2+) promotes lipid oxidation of linoleic acid leading to the development of hexanal, a major off-flavour compound in iron fortified maize meal porridge. Findings from this study indicate that a change from fortifying maize meal with electrolytic iron to NaFeEDTA will not lead to changes in appearance and flavour of maize porridge. However, an excess amount of NaFeEDTA (30 mg iron/kg maize meal) might lead to acceptability (taste) problems if porridge is prepared in cast iron cookware. Fortification of maize meal porridge with a more bioavailable source of iron (NaFeEDTA) may reduce the prevalence of iron deficiency in South Africa.