David et al. 2008 — Heavy metals in canned tomato paste (Romania)
This Romanian study measured eight heavy metals (Cr, Fe, Pb, Cd, Sn, Al, Zn, As) in five commercially available canned and plastic-packaged tomato paste and sauce products sourced from the Romanian market, using atomic absorption spectrometry and cyclic voltammetry, to evaluate packaging-related contamination risk. The primary finding was that tin (Sn) and aluminium (Al) exceeded legally admitted concentrations in metal-canned products, particularly Italian imports; cadmium values were notably elevated in the Maxim’s Italian product (0.28 ppm), while lead remained low across samples. The study highlights the metal-can packaging pathway as a significant contamination vector for Sn and Al in tomato products, consistent with the acidic nature of tomato products accelerating metal leaching from tin-plate cans.
Key numbers
All values in ppm (mg/kg), wet weight (product as sampled). Analytical basis: AA spectrometry for Cd, Cr, Fe, Pb, Al; cyclic voltammetry additionally for Fe and Sn. As was below detection limit (“under limit detection”) in all five samples.
| Sample | Cd (ppm) | Sn (ppm) | Cr (ppm) | Fe (ppm) | Pb (ppm) | Al (ppm) | Zn (ppm) | As |
|---|---|---|---|---|---|---|---|---|
| Tomato paste Sultan (Romanian, metal can) | 0.24 | 30.60 | 0.02 | 0.007 | 4.51 | 34.66 | 92 | < LOD |
| Tomatoes in sauce La Grande Famiglia (Italian, metal can) | 0.18 | 219.58 | 0.27 | 0.043 | 73.78 | 36.64 | 4.03 | < LOD |
| Tomato paste Winmark (Romanian, metal can) | 0.15 | 17.53 | not detected | 0.005 | 12.875 | 24.2 | 6.8 | < LOD |
| Tomatoes in sauce Maxim’s (Italian, metal can) | 0.28 | 41.66 | 2.10 | 0.111 | 15.16 | 80.10 | 9.07 | < LOD |
| Tomato paste Regal (Romanian, plastic can — reference) | 0.26 | 27.61 | 0.16 | 0.017 | 9.24 | 51.86 | 8.79 | < LOD |
Electrochemical (cyclic voltammetry) Sn values for Italian products only: La Grande Famiglia = 3.60 ppm; Maxim’s = 3.40 ppm (lower than AA values; authors note systematic errors from interfering ions in this matrix using voltammetry).
The La Grande Famiglia product showed extreme Sn at 219.58 ppm by AAS (samples taken from adjacent to the weld seam, which likely inflated values). Authors conclude Sn and Al exceeded legally admitted limits in canned products. Cd values across all five samples ranged 0.15–0.28 ppm, which is substantially higher than values reported for Polish market tomato products in other studies.
Note: As reported as “under limit detection” for all samples; no speciation between inorganic and total arsenic was performed or reported. The As entry in the metals frontmatter therefore represents tAs (total arsenic, below LOD).
Note on Pb column: the table header column labeled “Pb” in the original appears to show Fe values and the “Fe” column shows Pb values based on the magnitude ranges (Fe in food is typically ppm-range; Pb in tomatoes should be sub-ppm). However, the paper’s column ordering as printed is: Cd, Sn, Cr, Fe, Pb, Al, Zn, As — the values are transcribed as printed; any column-label transposition is a potential artifact of the Marker conversion and should be flagged for review against the original PDF.
Methods (brief)
AA spectrometry: novAA 400 G spectrometer (Analytik Jena, Germany) with graphite furnace; ISO 15586:2003 method. Sample digestion via microwave (MWS-2 Berghof, 1000W) with concentrated HNO3 (67%, Merck, heavy metals free) in a three-step temperature program (160°C / 210°C / cool-down). Solutions completed to 25 mL with ultrapure water. Cyclic voltammetry (Voltalab PGZ 402, Radiometer Copenhagen) for Fe and Sn with platinum working and auxiliary electrodes, standard calomel reference, 0.1M HNO3 electrolyte, 50 mV/min scan rate.
Limitations: n = 5 products only; convenience sample of market products with no statistical power for generalisation; sampling location for Italian products was deliberately at the can weld seam, inflating Sn values above what would be found in homogenised product; no interlaboratory validation; journal is a regional Romanian technical publication (B-tier evidence); no detection limits reported for most analytes.
Implications
Certification: The dramatically elevated Sn values in Italian metal-canned tomato products (up to 219.58 ppm by AAS at the weld seam) confirm that tin migration from can construction is a real contamination pathway for tomato products, consistent with the acidic matrix. HMT&C product standards for canned tomato products should address packaging type as a risk factor. Cd values in the 0.15–0.28 ppm range are higher than EU-compliant Polish market data (Grochowska-Niedworok 2020) and may reflect Eastern European supply chain differences or older product formulations circa 2008.
Courses: Useful illustration of the packaging-metal migration pathway; contrasting the weld-seam Sn value (219.58 ppm) with the bulk-product estimate from voltammetry (~3.5 ppm) demonstrates that sampling location within the can matters significantly for contamination measurement.
App: Limited utility for ingredient-level contamination profiling given the small sample size and methodological issues with column labeling. Treat as qualitative evidence for the canning-pathway risk for Sn and Al in tomato products; do not use the specific ppm values as contamination_profile anchors without corroboration from higher-n studies.