Heavy Metal Index

Assessment of essential and non-essential metals in popcorn and cornflake commercially available in Ethiopia

4 min read

Source access

Publication
Chemistry International 3(3):268-276
Year
2017
Authors
Abebe A; Chandravanshi BS; Debebe A
Source type
peer reviewed
License
open access (regional journal)

Abebe et al. 2017 — Essential and toxic metals in Ethiopian popcorn and cornflake

This study uses flame and graphite-furnace atomic absorption spectrometry to quantify 13 metals (K, Na, Mg, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pb, Cd) in popcorn and cornflake commercially available in Addis Ababa, Ethiopia. Popcorn samples were prepared by the traditional oil-popping method; cornflakes were imported from Egypt and purchased at supermarkets. Cd and Ni were below detection in both products. Pb was elevated in popcorn (0.94 ± 0.29 mg/kg) and lower but present in cornflake (0.36 ± 0.03 mg/kg) — both substantially above the EU 2023/915 0.020 mg/kg limit for cereals as placed on market. Chromium (0.68 mg/kg popcorn, 0.30 mg/kg cornflake) is also elevated relative to typical cereal Cr ranges. Population: regional sourcing, small n (8 total samples), B-tier evidence. Useful as a contributor to the cornflake/popcorn ingredient-page evidence pool.

Key numbers

Per-product mean ± SD concentrations (mg/kg dry weight):

MetalPopcorn (n=5 pooled to 1)Cornflake (n=3)
K1293 ± 233612 ± 70
Na148 ± 3410 ± 5
Mg387 ± 11323 ± 11
Ca97.9 ± 4.2196 ± 99
Cr0.68 ± 0.090.30 ± 0.07
Mn6.17 ± 0.183.0 ± 0.1
Fe9.5 ± 2.15.5 ± 0.74
Co1.41 ± 0.160.32 ± 0.03
Cu0.09 ± 0.0070.30 ± 0.01
Zn88.3 ± 9.740.7 ± 2.5
Pb0.94 ± 0.290.36 ± 0.03
Cd<DL<DL
Ni<DL<DL

Most metals are higher in popcorn than cornflake, attributable to the cornflake processing steps (cooking, leaching during flake formation) removing some of the mineral content. The exceptions — Na, Ca, Cu — are higher in cornflake, likely from added salt (Na), hard processing water (Ca), and metal contact during manufacture (Cu).

Regulatory comparison:

  • EU 2023/915 Pb limit for cereals (as placed on market, dry weight): typically 0.10-0.20 mg/kg depending on cereal class
  • Ethiopian popcorn Pb 0.94 mg/kg: ~5-9x the EU ceiling
  • Ethiopian cornflake Pb 0.36 mg/kg: ~2-4x the EU ceiling

The “samples were free from the toxic metals Cd and Ni, but not from Pb” finding is the headline. Pb contamination in Ethiopian-market popcorn at nearly 1 mg/kg dry weight is a significant supply-chain or growing-environment Pb source — likely traceable to soil-Pb in maize-growing regions of Ethiopia or to atmospheric deposition from regional Pb sources.

Methods

Sample collection: 5 popcorn samples (~200 g each, ~1 kg total) from open market in Addis Ababa, pooled and homogenized. 3 cornflake packs (~500 g each) imported from Egypt, also homogenized.

Sample prep: 1.0 g powdered sample + 10 mL of HNO3:HClO4:H2O2 (6:2:2 v/v) digested 3 hours at 120 °C in Kjeldahl apparatus. 10 mL deionized water added post-digestion, dissolution-cleaned, 0.67 g La(NO3)3·6H2O added to prevent Ca/Mg precipitation, dilute to 50 mL, filter Whatman 541. Spike-recovery 91.2-109% (within ICH acceptance).

Instrumentation:

  • FAAS (Analytikjena ZEEnit 700P, VGP AAS) with deuterium background correction + hollow cathode lamps + air-acetylene flame: K, Na, Mg, Ca
  • GFAAS (PerkinElmer AAnalyst 600) with >99.99% argon: Cr, Mn, Fe, Co, Ni, Cu, Zn, Pb, Cd

Calibration: four-point working standards prepared freshly from intermediate (10 mg/L) prepared from stock (1000 mg/L). Correlation coefficients >0.997.

Speciation: Total metals only.

Implications

Certification: For HMTc Cat 1 / Cat 3 grain product rows + the Ethiopian regional context:

  1. Ethiopian popcorn carries notably elevated Pb (~1 mg/kg, 5-9x EU ceiling). This is a regional sourcing concern but maize is a global ingredient; HMTc Cat 1 corn-flake-based and popcorn-based baby snacks should require origin-country audits and supplier COA testing.

  2. Cd and Ni were below detection in both products. This is a cleaner Cd-and-Ni baseline than other commodity surveys have shown. May reflect East African geology (not naturally Cd-rich), Ethiopian agricultural practices (low phosphate-fertilizer Cd input vs other regions), or sampling fortune.

  3. Cornflakes processing reduces most metal contents but elevates Na/Ca/Cu via salt addition, hard water, and metallic-contact contamination. HMTc Cat 1 cornflake-based baby cereal certification should track this processing-induced metal-load shift.

  4. B-tier evidence: regional journal, no DOI, small sample size (n=8). Useful as a corroborative source but not a load-bearing primary reference for HMTc threshold-setting. Higher-tier corn / cornflake / popcorn references should be sought.

Courses: Useful for an East African food-safety case study. The traditional oil-popping method’s effect on metal levels is implicit in the popcorn-vs-cornflake comparison.

App: For consumer-facing app, Ethiopian-market or East-African-market popcorn should be flagged for elevated Pb risk based on this small dataset. US/EU market popcorn is generally cleaner (most US popcorn Pb <0.1 mg/kg per FDA surveys).

Microbiome: Not addressed.

Wiki pages updated on ingest