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Essential minerals and their potential bioavailability in popcorn (Zea mays L. subsp. everta (Sturtev.) Zhuk.) kernels and flakes

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Overview

This Chilean Journal of Agricultural Research paper measured Ca, Mg, Fe, Cu, Mn, Zn and phytic phosphorus in kernels and microwave-popped flakes of 12 popcorn (Zea mays subsp. everta) hybrids grown 2021-2022 at the Maize Research Institute Zemun Polje, Serbia. The study is a bio-fortification and nutritional-bioavailability investigation; HMI-scope heavy metals (Pb, Cd, iAs, tAs, MeHg, tHg, Ni, Al, Cr, Cr-VI, Sn, Sb, U) are NOT measured in the present work — Cd, As, Pb, and Ni appear only in the literature-review framing, citing Abebe et al. 2017 and Dada & Kutu 2022 on lower accumulation of potentially toxic elements in popcorn maize. Microwave popping decreased phytic acid concentration up to 11.8% in flakes of six hybrids (541/1k, ZP 542/1k, ZP 657/1k, ZP 644/1k, ZP 557/1k, ZP 686/1k), improving potential bioavailability of essential elements.

Key numbers

  • Hybrids/sampling: 12 popcorn hybrids (H1-H12); 4 field replicates per hybrid; field-trial soil characteristics (slightly calcareous Chernozem; 51.0% sand, 31.0% silt, 18.0% clay, 3.5% organic matter, pH 7.0 KCl / 7.5 H₂O); concentrations expressed on dry-weight basis after drying at 105 °C to constant weight (4 h) (p. 278-279).
  • Essential mineral concentrations across 12 hybrids (Table 4, µg/g dry weight; authors report identical kernel and flake values on a DW basis): Ca 103.3 ± 0.5 (H12) to 425.2 ± 24.1 (H5); Mg 1620.4 ± 51.6 (H12) to 2094.7 ± 66.8 (H11); Fe 31.03 ± 0.86 (H5) to 55.75 ± 0.81 (H10); Cu 6.79 ± 0.19 (H11) to 37.32 ± 2.95 (H1); Mn 9.57 ± 1.40 (H12) to 15.62 ± 0.56 (H7); Zn 32.40 ± 1.14 (H9) to 69.15 ± 0.29 (H10) (Table 4, p. 281).
  • Phytic P (Pphy): kernels 2.94 ± 0.07 (H1) to 3.50 ± 0.04 (H6) mg/g; flakes 2.78 ± 0.01 (H10) to 3.46 ± 0.02 (H7) mg/g. Microwave popping reduced Pphy “up to 11.8%” in flakes of 541/1k, ZP 542/1k, ZP 657/1k, ZP 644/1k, ZP 557/1k, ZP 686/1k (Abstract; Table 3, p. 281).
  • Molar ratios (Table 6, p. 283): lowest Phy/Mg in H10 kernels (0.190 ± 0.027) and H10 flakes (0.176 ± 0.007); lowest Phy/Fe in H10 kernels (7.06 ± 0.22) and H10 flakes (6.51 ± 0.26); lowest Phy/Zn in H10 kernels (5.69 ± 0.15) and H10 flakes (5.25 ± 0.34); lowest Phy/Mn in H7 kernels (25.54 ± 0.52) and H10 flakes (24.85 ± 0.64); lowest Phy/Cu in H1 kernels (23.29 ± 0.14) and H1 flakes (26.12 ± 0.27); lowest Phy/Ca in H5 kernels (1.580 ± 0.150) and H5 flakes (1.466 ± 0.164).
  • Kernel yield 4.99 ± 0.19 (H10) to 6.77 ± 0.14 (H1) t/ha; popping volume 29.00 ± 1.41 (H3) to 40.09 ± 0.12 (H7) cm³/g; kernel size 60.00 ± 2.52 (H6) to 82.00 ± 3.76 (H3) kernels per 10 g; un-popped kernels 0.66 ± 0.03% (H12) to 4.57 ± 0.21% (H3) (Table 3, p. 281).
  • Heavy-metal context (literature-review only, NOT measured in this study): authors cite Abebe et al. 2017 and Dada & Kutu 2022 reporting that accumulation of potentially toxic elements (Cd, As, Pb, Ni) is lower in popcorn maize even when grown on municipal-solid-waste-compost-fertilized soil, and that popping decreases K, Mg, Cr, Mn, Fe, Co, Pb concentrations while increasing Na, Ca, Cu, Zn (p. 277-278). These are cited prior-literature observations, not original measurements of the present paper.

Methods (brief)

Two-year field trial (2021, 2022) at Maize Research Institute Zemun Polje, Belgrade, Serbia (44°52’ N, 20°19’ E, 81 m a.s.l.), slightly calcareous Chernozem under rain-fed conditions; preceding crop winter wheat both years; 100 kg/ha mono-ammonium phosphate (MAP) incorporated each autumn (2020, 2021) plus 250 kg/ha urea (spring 2021) and 280 kg/ha urea (spring 2022). Twelve hybrids in 6.2 m² plots (40 plants, 70 cm inter-row, 22 cm intra-row), fully randomized block design, 4 replicates, sown first week of May.

After harvest, kernel moisture brought to 14% (drying at 40 °C), kernel yield calculated. Popping: 4 × 100 kernels per replicate in a paper bag, Samsung 1.1 cu. Ft 1000 W microwave oven, 5 min, no oil/salt/sugar. Kernels and flakes milled to <500 µm (Perten Laboratory Mill 120, PerkinElmer, Stockholm, Sweden) and dried to constant weight at 105 °C / 4 h (EUGE425 ventilation oven, EU Instruments, Novo Mesto, Slovenia) for dry-weight basis.

Phytic P determined by Wade reagent spectrophotometry (Dragičević et al. 2011 method; reagent containing 0.3 g FeCl₃·6H₂O and 3 g 5’-sulfosalicylic acid in 1 L) at λ = 500 nm on a Libra S22 UV/Vis spectrophotometer (Biochrom, Cambridge, UK). Essential mineral analysis (Ca, Mg, Fe, Mn, Cu, Zn) by inductively coupled plasma optical emission spectroscopy (ICP-OES, iCAP 7000 Series dual-view, Thermo Scientific, Waltham, Massachusetts, USA), following AOAC procedure (Helrich 1990). Popping volume measured by metric weight volume test on a Cretors 2300W official metric weight volume tester (Cretors, Wood Dale, Illinois, USA). Statistics: ANOVA with Fisher’s LSD at p < 0.05; PCA in MATLAB R2011a with PLS Toolbox v.6.2.1 (mean-centred, auto-scaled, SVD algorithm, 95% confidence level for Hotelling T² limits).

Limitation for HMI scope: HMI-scope toxic metals (Pb, Cd, iAs, tAs, MeHg, tHg, Ni, Al, Cr, Cr-VI, Sn, Sb, U) were NOT measured in this study. The paper does not report LODs/LOQs for any element. All numeric values are essential-nutrient concentrations, not contaminant occurrence data.

Implications

  • Certification (HMTc): No direct contribution. The paper does not measure any of the 10 HMTc analytes (Pb, tAs, Cd, MeHg, tHg, iAs, Ni, Al, Cr-VI, Sn) or the broader HMI metal vocabulary (which adds Cr, Sb, U). It is useful as a methodology reference for ICP-OES on maize-grain matrices and as a citation pointer to Abebe et al. 2017 and Dada & Kutu 2022, which do report heavy metals in popcorn.
  • Courses: Teachable contrast between bio-fortification literature (essential-element framing) and contamination literature (toxic-element framing), and how the wiki must distinguish essential trace elements (Cu, Mn, Zn, Fe) from toxic species (Pb, Cd, iAs, etc.) when they share analytical platforms.
  • App: Does not advance any HMTc analyte sub-block on Corn or maize. The Ca, Mg, Fe, Cu, Mn, Zn data are out of scope for the contamination_profile schema.
  • Routing fan-out: matrix popcorn maps to [[products/snacks-crackers-biscuits]] per the structured evidence record; the source contributes context (not occurrence evidence) to that product page.

Update history

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