Nutritional Composition of Iron, Zinc, Calcium, and Phosphorus in Wheat Grain Milling Fractions as Affected by Fertilizer Nitrogen Supply

Fe and Zn deficiencies are global nutritional problems. N supply could increase Fe and Zn concentrations in wheat grain. This study was conducted to determine the impacts of different N rates (0, 122, 174, and 300 kg/ha) on the distribution and speciation of Fe and Zn in wheat grain milling fractions under field conditions. Zn and protein concentrations were increased, whereas Fe was less affected in the flour fractions with increasing N rates. Further analysis with size-exclusion chromatography coupled with inductively coupled plasma mass spectrometry revealed that Fe and Zn bound to low-molecular-weight (LMW) compounds in the flour fractions (probably Fe-nicotianamine [NA], Fe-deoxymugineic acid, or Zn-NA) were less affected by increasing N supply, representing 3.5–10.9% of total Fe and 2.5–56.6% of total Zn. In the shorts fraction, LMW-Fe was absent, and LMW-Zn with higher N supply was over twice as high as that in control and 3–27 times as high as that in the other milling fractions. In the flour frac...