Iron bioavailability of maize is improved by degermination for some but not all genotypes: enhancing maize nutrition with biofortification and processing

Authors: KIEGLER, JOHANNA - Former ARS Employee; Wiesinger, Jason; Flint-Garcia, Sherry; Glahn, Raymond

Submitted to: Frontiers in Sustainable Food Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2023
Publication Date: 3/6/2023
Citation: Kiegler, J.I., Wiesinger, J.A., Flint Garcia, S.A., Glahn, R.P. 2023. Iron bioavailability of maize is improved by degermination for some but not all genotypes: enhancing maize nutrition with biofortification and processing. Frontiers in Sustainable Food Systems. vol. 14. https://doi.org/10.3389/fpls.2023.1114760.
DOI: https://doi.org/10.3389/fpls.2023.1114760

Interpretive Summary: Maize is a staple food for many communities with high levels of iron deficiency anemia. Improving iron nutrition from maize via plant breeding and or processing can aid in alleviating iron deficiency anemia. Previous studies of only a small number of maize and supermarket products indicated that degermination of the maize kernel could improve the Fe bioavailability from maize. Therefore, the objective of this study was to expand this research and evaluate bioavailable iron and factors that influence iron bioavailability in a broader collection of maize varieties. The results confirm previous research showing that the germ fraction is a strong inhibitory component for many maize varieties. Degermination greatly reduced phytate content, a known inhibitor of Fe bioavailability and certainly contributed to improved iron uptake from some but not all samples. Other factors in the maize germ and endosperm fractions are likely involved in the effects of degermination on Fe bioavailability. This study suggests that Fe nutrition from maize can be enhanced via degermination and or by selecting genotypes where the inhibitory effect of the germ fraction is relatively low.

Technical Abstract: Maize is a staple food for many communities with high levels of iron deficiency anemia. Improving iron bioavailability in maize via biofortification and processing can aid in alleviating iron deficiency anemia. Previous studies of only a small number of maize and supermarket products indicated that degermination could improve the Fe bioavailability from maize. Therefore, the objective of this study was to expand this research and evaluate bioavailable iron, iron concentrations, and phytate concentrations of whole and degerminated (germ fraction removed) maize with a Maize Nutrition Panel (MNP) of 52 diverse genotypes. Both whole and degerminated maize samples were cooked, lyophilized, and milled to produce pre-cooked corn flour. Iron bioavailability was evaluated with the Caco-2 cell bioassay, mineral concentrations were measured using ICP-EMS, and phytate concentrations were determined using Phytic Acid assay kits (Megazyme International, Ireland). In 30 of the maize genotypes, bioavailable Fe increased when degerminated, thus indicating a higher fractional Fe uptake as the amount of Fe decreased by more than 70%. The remaining 22 genotypes showed no change or a decrease in Fe bioavailability with degermination. These results confirm previous research showing that the germ fraction is a strong inhibitory component for many maize varieties. Degermination greatly reduced phytate content and phytate:Fe molar ratio; Fe concentrations were positively correlated with phytate, and negatively correlated with phytate:Fe molar ratios for most maize groups. However, there was no significant panelwide correlation between bioavailable Fe and phytate or phytate:Fe molar ratio. Other factors in the maize germ and endosperm fractions are likely involved in the effects of degermination on Fe bioavailability. This study suggests that Fe nutrition from maize can be enhanced via degermination and or by selecting genotypes where the inhibitory effect of the germ fraction is relatively low.