The effects of hydrothermal processing and germination on Fe speciation and Fe bioaccessibility to human intestinal Caco-2 cells in Tartary buckwheat

Tartary buckwheat is a gluten-free crop with great potential as a wheat substitute. Iron (Fe) is an important mineral element in staple foods which is required in sufficient bioaccessible quantities. The aim of the study was to investigate how processing of grains into groats (hydrothermal processing to remove the husk) and sprouts (7-day-old seedlings) affected Fe speciation (Fe2+ or Fe3+), Fe ligand composition and Fe bioaccessibility to human Caco-2 cells. Groats contained the least Fe (23.8 ± 1.65 mg kg−1) and the lowest amounts of Fe2+ (8%). Grains and sprouts had comparable Fe concentrations (78.2 ± 2.65 and 68.9 ± 2.73 mg kg−1) and similar proportions of Fe2+ (15% and 18%). The main ligands for Fe in Tartary buckwheat material were phytate and citrate. Phytate was less abundant in sprouts, which did not correlate with greater Fe bioaccessibility. Iron bioaccessibility was 4.5-fold greater for grains than groats, suggesting that Fe is more bioaccessible in the husk than in the rest of the grain.