Overview
The authors quantified aluminum migration from aluminum foil into six controlled cooking-solution recipes built on a 40% minced-beef extract base, with tomato juice, citric acid, salt, apple vinegar, and spices used as acidifying and seasoning vehicles. Foil and pan contact was tested in three modes: liquid-phase immersion at boiling temperature for 2 hours, vapor-phase exposure above boiling solution for 2 hours, and oven baking at 185°C for 1.5 hours in an aluminum pan covered with aluminum foil. Aluminum mass loss was determined gravimetrically (weight-loss corrosion-rate measurement); the surface morphology of the foil before and after contact was imaged by environmental scanning electron microscopy (ESEM) with energy-dispersive X-ray; and aluminum content of the contacted solutions was determined by ICP-MS for two recipe variants. The work is small (single laboratory, two replicates per condition, no compositional characterisation of the foil alloy, only two ICP-MS values reported) and the gravimetric “intake” figures depend on a per-meal extrapolation chain (per-person serving derived as one-third of the dish weight) that the wiki preserves but flags. It is included as evidence on the food-contact-materials route because the magnitudes are large and consistent with the broader foil-leaching literature.
Key numbers
Two reporting bases are present in the paper. ICP-MS results are reported as aluminum concentration in the cooked solution (ppb = µg/L). Weight-loss results are reported as the foil mass dissolved (mg), as a corrosion rate (mg·cm⁻²·hr⁻¹), and as an extrapolated per-person aluminum intake (mg/person) under a stated assumption that the cooking pan serves three people. The pH of each recipe is measured before exposure. Letters in parentheses below refer to the paper’s Solution numbering, which is recipe-set-specific: the Solution (1) recipe in Table 1 differs from the Solution (1) recipe in Table 2 (see §2.2.1.1 vs §2.2.1.2 and the table footnotes), so values are reported with the table source attached.
- ICP-MS aluminum content in the cooked solution after foil contact: 21,160.9 ppb (µg/L) for Solution (1) and 19,915.8 ppb for Solution (2) (§3.3, p. 4508). The recipe specification for the ICP-MS arm is not separately tabulated; both solutions are described in §3.3 as “the two food solutions” following the oven-work liquid-phase experiments.
- Table 1 (liquid- and vapor-phase weight-loss, 10 cm² foil area, 2 h at boiling, drinking water; p. 4502). Per-person aluminum intake is computed by extrapolating the 10 cm² loss to the foil surface area of a circular pan of 22, 30, and 40 cm diameter (areas ≈ 380, 707, and 1257 cm²) and dividing by 3:
- Solution (1) — 250 ml 40% beef extract + 250 ml tomato juice + 3 g citric acid + 5 g salt; pH 3.7. Vapor: weight loss 1.7 mg, corrosion rate 8.5 ×10⁻² mg·cm⁻²·hr⁻¹, intake 21.1 / 39.4 / 69.6 mg/person at D=22 / 30 / 40 cm. Liquid: 1.8 mg, 9.0 ×10⁻², 22.8 / 42.4 / 75.4 mg/person.
- Solution (2) — 250 ml 40% beef extract + 250 ml tomato juice + 20 g citric acid + 5 g salt; pH 2.8. Vapor: 3.3 mg, 16.6 ×10⁻², 42.1 / 78.1 / 139.2 mg/person. Liquid: 3.2 mg, 15.8 ×10⁻², 40.0 / 74.4 / 132.4 mg/person.
- Table 2 (liquid-phase weight-loss, foil area 64 cm² with extrapolation to a 22 cm diameter pan = 380 cm², 2 h at boiling; p. 4503). All six recipes use drinking water unless noted:
- Solution (1) — 250 ml 40% beef extract + 250 ml tomato juice + 10 g citric acid + 5 g salt; pH 3.2. Weight loss 16.7 mg, corrosion rate 13.1 ×10⁻² mg·cm⁻²·hr⁻¹, intake 33.05 / 61.5 / 109.4 mg/person at D=22 / 30 / 40 cm.
- Solution (2) — 20 g citric acid; pH 2.8. 20.2 mg, 15.8 ×10⁻², 40.0 / 74.4 / 132.4 mg/person.
- Solution (3) — same recipe as Solution (2) but prepared with tap water instead of drinking water; pH 3.2. 9.9 mg, 7.75 ×10⁻², 19.7 / 36.7 / 65.2 mg/person. The tap-water variant leaches roughly half the drinking-water value, attributed by the authors to pH.
- Solution (4) — citric acid replaced with 30 ml apple vinegar (acetic acid); pH 4.2. 70.9 mg, 55.5 ×10⁻², 140.3 / 261 / 465.0 mg/person at D=40 cm. This is the highest intake value in Table 2; the authors state that this single meal would deliver what the WHO TDI permits across about 7 days.
- Solution (5) — Solution (2) plus 3 g spices; pH 3.0. 82.0 mg, 64.1 ×10⁻², 162.3 / 302.0 / 537.2 mg/person at D=40 cm. Highest in the dataset overall.
- Solution (6) — 500 ml 40% beef extract + 20 g citric acid + 5 g salt (no tomato juice); pH not reported. 18.7 mg, 14.61 ×10⁻², 37.0 / 68.8 / 122.2 mg/person. Comparable to Solution (2), which the authors interpret as the tomato-juice addition having little effect once citric acid and salt are already present.
- Oven baking (§3.2, p. 4507). A 22 cm aluminum pan half-filled with 375 ml 40% beef extract + 375 ml tomato juice + 30 g citric acid + 7.5 g salt, covered with aluminum foil, baked 1.5 h at 185°C. Total aluminum dissolved from the pan: 1,000 mg, equivalent to 333.3 mg/person under the three-person extrapolation. Combined pan + foil dissolution: 361 mg/person. A rectangular 60×40 cm foil piece alone yields 174.3 mg/person; a 22 cm² circular foil yields 27.7 mg/person under the same conditions (Figure 5 linear fit: intake = 0.0726 × area (cm²) + 0.0431, R² = 1).
- ESEM imaging (Figures 3–4, §3.1.1, and Figure 6, §3.2.1): pristine aluminum-foil surface shows a smooth rolled-finish texture; after 2 h immersion in Solution (2) at boiling temperature the surface is densely pitted, and after 1.5 h oven exposure at 185°C the foil is “almost completely damaged” with extensive cracking and flaking. The imaging is qualitative confirmation of the dissolution mechanism, not quantitative.
- Reference TDI context cited from the literature (not measured here): WHO tolerable daily intake 1 mg aluminum / kg body weight / day (WHO Food Additives Series 46, 2001 — reference [1] in the source).
- The paper reports as background context (§1, p. 4499) the prior Turhan (2006) finding that cooking increases aluminum concentration by 89–378% in red meats and 76–215% in poultry when wrapped in foil at 150°C / 60 min through 250°C / 20 min, and the Ekanem et al. (2009) range of 59.83–220.20 mg/kg for 1–3 h beef baked in aluminum foil. These are cited, not re-measured.
Methods (brief)
Foil specimens were cut from sheet stock purchased on the local UAE market (no alloy composition reported; no manufacturer or alloy designation given). Liquid-phase weight-loss specimens were 8 × 4 cm with a 1 mm suspension hole; vapor-phase specimens were 2.5 × 2 cm. For the oven-work arm, the foil was a circular cover sized to the pan diameter (22, 30, or 40 cm), and the pan itself was a 22 cm “Indian aluminum pan” (the descriptor refers to a pan style/origin, not a brand). All weight measurements used a four-digit balance. Specimens were rinsed with distilled water followed by acetone after exposure and reweighed. Corrosion rate CR = WL / (A · T), with WL in mg, A in cm², T in hours.
Six cooking-solution recipes were assembled from 40% minced-beef extract obtained by boiling minced beef in drinking water for one hour and filtering to recover the extract, then mixed with tomato juice, citric acid, salt (NaCl), and — in two recipes — 30 ml apple vinegar or 3 g spices. pH was measured before exposure. Liquid-phase samples were immersed in the boiling solution for 2 h; vapor-phase samples were suspended in the vapor space above the same boiling solution for 2 h. Oven-work samples were baked at 185°C for 1.5 h. All conditions in duplicate.
ESEM/EDX surface imaging was performed on the foil before and after each exposure mode. ICP-MS analysis was performed on the post-exposure cooking solutions for two recipes (Solution (1) and Solution (2)); the instrument vendor and model, digestion procedure, calibration standards, and quality-control materials are not specified in the source.
Speciation note: the paper reports total aluminum only; aluminum-speciation analysis was not performed and is not required for the food-contact-leaching question being asked.
Per-person intake calculation: the paper assumes a three-person serving for any given pan and divides the total foil/pan mass loss by 3 to derive mg/person. The 10 cm² weight loss in Table 1 is then linearly extrapolated to the larger pan footprints (380, 707, 1257 cm²) by surface-area ratio. The 65 cm² weight loss in Table 2 is similarly extrapolated to 380 cm². The implicit assumptions are uniform leaching across the foil surface area, complete transfer of dissolved aluminum to the food, and that the foil mass loss equals dissolved aluminum (no oxide-flake artefact correction). The wiki preserves the paper’s numbers without re-deriving them.
Implications
Certification: Direct evidence on aluminum migration from food-contact aluminum foil and from cookware-grade aluminum pans into acidic meat-cooking liquid and vapor. The data inform the food-packaging-foils-wraps row and the metal-alloy cookware row simultaneously, because the oven-work experiments cannot separate pan contribution from foil contribution (the §3.2 calculation attributes 333.3 mg/person to the pan and the remainder to the foil, but both are aluminum-leaching surfaces in the same cooking vessel). The per-person intake values reported here are large in relation to the WHO TDI cited by the source (1 mg/kg bw/d, reference [1]); the paper’s own published characterisation is that the apple-vinegar Solution (4) at 465 mg/person delivers in one meal what the WHO TDI permits across about seven days (§3.1, p. 4504). The 537.2 mg/person figure for Solution (5) is the largest value in the dataset; the paper does not compute a TDI-equivalent for it. Read with the methodological caveats above: the small number of replicates (n=2 per condition), absence of foil alloy characterisation, single ICP-MS comparison point, and three-person serving assumption all temper the strength of inference. A more recent foils-route study with five characterised foils and six replicates per condition is Dordevic et al. 2019 (Aluminum contamination of food during culinary preparation: Case study with aluminum foil and consumers' preferences).
Courses: Useful as a teaching example for acid-driven dissolution of the protective Al₂O₃ film (the Al₂O₃ + 6H⁺ → 2Al³⁺ + 3H₂O reaction is written out in §3.1, p. 4505), for the pH-leaching relationship across recipes (Sol 2 at pH 2.8 vs Sol 4 at pH 4.2 — acetic acid produces more leaching than citric acid at higher nominal pH, attributed to complexing chemistry rather than pH alone), and for the spice-driven amplification observed in Solution (5). The ESEM before-and-after images (Figures 3–4 and 6) are usable as visual evidence of the dissolution mechanism for non-specialist audiences.
App: The aluminum contamination_profile cell for the foils/wraps product row and for the metal-alloy cookware row receives a contribution here. Ingredient-page aluminum cells for beef, tomato, salt, spices, and apple cider vinegar should treat the values reported in this paper as cooking-method context (Al from foil and pan contact during boiling, vapor exposure, or oven baking) rather than as intrinsic-ingredient occurrence. The app should warn on acidic-food preparation in direct aluminum-foil or uncoated-aluminum-pan contact, not on the ingredients themselves.
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