Muniz et al. 2018 — Metals in tomato sauces by packaging type, Brazil
Twenty commercial tomato sauce samples across four packaging types (plastic, metallic/canned, cellulosic, and glass) from Rio de Janeiro supermarkets were analysed by ICP-MS for As, Cd, Pb, Cr, Ni, Sb, and Sn. The study found that As, Cd, and Pb were all below Brazilian regulatory limits across all packaging types, and no significant difference between packaging types was found for most metals. The critical findings were that Cr exceeded Brazil’s maximum permissible level (0.1 mg/kg) in all packaging types (mean values 0.27–0.39 mg/kg), and Sn was significantly higher in metallic/canned packaging (0.125–0.258 mg/kg) than in plastic, cellulosic, or glass containers, with tin migration from can linings confirmed by simulant solution testing.
Key numbers
Metal concentrations by packaging type (mg/kg, n=20 total):
| Analyte | Plastic (n=7) | Metallic/Can (n=7) | Cellulosic (n=4) | Glass (n=2) | Brazil ML |
|---|---|---|---|---|---|
| As | 0.029 ± 0.005 | 0.030 ± 0.005 | 0.035 ± 0.013 | 0.029 ± 0.0005 | 0.5 mg/kg |
| Cd | 0.004 ± 0.002 | 0.004 ± 0.001 | 0.006 ± 0.002 | 0.005 ± 0.001 | 1.0 mg/kg |
| Pb | 0.016 ± 0.008 | 0.038 ± 0.009 | 0.049 ± 0.033 | 0.020 ± 0.010 | 0.5 mg/kg |
| Cr | 0.30 ± 0.06 | 0.276 ± 0.08 | 0.322 ± 0.05 | 0.39 ± 0.04 | 0.1 mg/kg (exceeded) |
| Ni | 0.049 ± 0.007 | 0.100 ± 0.010 | 0.090 ± 0.033 | 0.074 ± 0.026 | 5.0 mg/kg |
| Sb | <0.018 (all) | <0.018 (all) | <0.018 (all) | <0.018 (all) | 2.0 mg/kg |
| Sn | 0.020–0.051 | 0.125–0.258 | 0.055–0.080 | 0.057–0.059 | 250 mg/kg |
Key contrasts:
- Sn was the only element with significantly different concentrations between packaging types (p<0.05), with metallic cans having 3–5x higher Sn than non-metallic packaging.
- Ni was significantly higher in metallic packaging (0.100 ± 0.010 mg/kg) vs plastic (0.049 ± 0.007 mg/kg).
- Cr mean values were 2.7–3.9x above Brazil’s 0.1 mg/kg limit in every packaging type tested. The authors attribute this to chromium in the raw material rather than packaging migration (Cr migration from packaging simulants was below LOQ).
Packaging composition by XRF: Cr detected in plastic (155 ± 23 mg/kg), cellulosic (74 mg/kg), and metallic can inner surface (0.05% w/w); Sn detected only in metallic can (1.32% w/w). Pb detected only in glass at very low concentration (0.003% w/w). Cd, Sb, Ni not detected in any packaging.
Simulant solution migration (GF-AAS): Sn migration from metallic can simulant: 0.067 mg/L. Cr migration from all packaging types: below LOQ (5 µg/L). Conclusion: Sn in canned tomato sauce comes from can lining dissolution; Cr contamination originates in the raw material, not from packaging.
Analytical methods: ICP-MS (Nexion 300D Perkin Elmer) for food samples, LOD/LOQ: As 0.095/0.32, Cd 0.014/0.047, Pb 0.15/0.50, Cr 0.034/0.11, Ni 0.40/1.33, Sb 0.18/0.61, Sn 0.17/0.57 µg/L. GF-AAS (PinAAcle 900Z Perkin Elmer) for simulant solutions. XRF (XL3t Thermo Scientific) for packaging composition.
Recovery ranges: As 74–94%; Cd 84–88%; Pb 77–93%; Cr 93–95%; Ni 102–106%; Sb 86–92%; Sn 54–83%.
Note on As: ICP-MS measured total arsenic (tAs). No speciation performed; iAs fraction not reported.
Methods (brief)
Cross-sectional analytical study. Twenty tomato sauce samples in four packaging types from Rio de Janeiro supermarkets (two brands: brand A with 12 samples in plastic/cellulosic/metallic; brand B with 8 samples in plastic/metallic/glass). Microwave digestion with HNO3 65%; ICP-MS using isotopes 75As, 111Cd, 208Pb, 52Cr, 60Ni, 121Sb, 118Sn, internal standard Rh at 10 µg/L. Simulant solution tests per Brazilian ANVISA legislation for each packaging type (acetic acid/NaCl/sucrose/tartaric acid as appropriate). XRF for packaging composition. No brand differences found for same packaging type, so results pooled by packaging. Recovery for Sn (54–83%) was at the low end; Sn values should be interpreted with some caution.
Implications
Certification: Critical finding: Cr in tomato sauce consistently exceeds Brazilian regulatory limits (mean 0.27–0.39 mg/kg vs 0.1 mg/kg limit) regardless of packaging. The EU Regulation 1881/2006 does not set a Cr ML for tomato sauce; only limits for fresh/raw vegetables exist. This points to a potential compliance gap in European/global markets. Sn migration from metallic cans (0.125–0.258 mg/kg) is measurable but 500–1000x below the 250 mg/kg tolerable limit. Neither Cd nor Pb nor As pose regulatory concerns in this product matrix at reported concentrations.
Courses: Illustrates the packaging-migration angle (Sn from cans, Cr from raw material) versus contamination-at-source distinction. The XRF packaging analysis plus simulant testing is a methodological teaching case for migration studies.
App: Tomato sauce Cd: ~0.004–0.006 mg/kg (4–6 µg/kg); Pb: ~0.016–0.049 mg/kg (16–49 µg/kg); Cr (total): ~0.27–0.39 mg/kg (270–390 µg/kg); Sn: ~0.020–0.258 mg/kg depending on packaging (canned 125–258 µg/kg). Note: total As ~0.029–0.035 mg/kg; no iAs speciation.