Abt, Fong Sam, Gray, Robin 2018 — Cd and Pb in cocoa powder and chocolate products, U.S. market
Summary
This FDA Center for Food Safety and Applied Nutrition convenience-sample survey measured cadmium and lead by ICP-MS in 144 cocoa powder, cocoa nib, dark chocolate, and milk chocolate products purchased at U.S. retail in December 2015 from 67 manufacturers. The authors evaluate Cd and Pb levels against percent cocoa content and reported geographic origin. Across the four matrices, mean Cd was highest in cocoa powder (0.70 mg/kg) followed by cocoa nibs (0.62), dark chocolate (0.27), and milk chocolate (0.06); mean Pb was highest in cocoa powder (0.11 mg/kg) followed by dark chocolate (0.03), milk chocolate (0.01), and cocoa nibs (0.003), with 54 of the lead samples reported at trace values. Cd and Pb concentrations correlated significantly with percent cocoa content; geographic variation was observed for Cd, with Latin American products carrying higher Cd than African products.
Key numbers
| Matrix | n | Mean Cd ± SD (mg/kg) | Mean Pb ± SD (mg/kg) |
|---|---|---|---|
| Cocoa powder | (subset of 144) | 0.70 ± 0.83 | 0.11 ± 0.10 |
| Cocoa nibs | (subset) | 0.62 ± 0.38 | 0.003 ± 0.004 |
| Dark chocolate | (subset) | 0.27 ± 0.25 | 0.03 ± 0.02 |
| Milk chocolate | (subset) | 0.06 ± 0.07 | 0.01 ± 0.01 |
| Range across all samples | Cd | Pb |
|---|---|---|
| Min | 0.004 mg/kg | <LOD |
| Max | 3.15 mg/kg | 0.38 mg/kg |
Cd and Pb were both significantly correlated with percent cocoa solids; correlation strengths varied by product type and geographic origin. Cd was higher in products from Latin America (Brazil, Ecuador, Peru) than from West Africa (Cote d’Ivoire, Ghana). Percent cocoa was available for 126 of the 144 product samples. The 26 cocoa-powder samples with 100 percent cocoa content had a mean Cd of 0.99 ± 0.87 mg/kg.
Methods (brief)
Convenience sample of cocoa powder (including cocoa drink mixes), dark chocolate, milk chocolate, and cocoa nib products from Prince George’s County, Maryland retail outlets and online vendors. 67 manufacturers represented. 20 g aliquots of cocoa powder and nibs were assayed; chocolate products were portioned consistent with FDA preparation protocols. Samples were frozen at -30°C, then digested and analyzed by ICP-MS per the FDA Elemental Analysis Manual procedure. Method accuracy verified against standard reference materials and reported in Table 2.
Limitations
This is a convenience sample and not a market-representative sample of U.S. cocoa-and-chocolate retail. Manufacturer information was used to assign geographic origin; not all 144 products had geographic-origin data confirmed independently. Percent cocoa was available for 126 of 144 products, so the percent-cocoa correlation analyses are over a subset rather than the full sample. The 2015 retail snapshot predates a number of subsequent supply-chain mitigation efforts in Latin American producer countries.
Implications
- Certification: Direct A-tier sample-level evidence base for Cd and Pb in cocoa powder, cocoa nibs, dark chocolate, and milk chocolate. Suitable for HMTc benchmark-pool admission for cocoa and chocolate ingredient and product rows after appropriate per-matrix-and-percent-cocoa stratification. The percent-cocoa-correlation finding implies that benchmark-pool aggregates over mixed-percent-cocoa products will conflate exposure-relevant variance and should stratify when sample size permits. The Latin America versus Africa Cd difference is large enough to require origin-disclosed certification when origin information is available; absent origin information, the certification floor should be set against the higher-Cd Latin America distribution rather than the African distribution.
- Courses: Strong worked example of how percent cocoa and geographic origin together explain a substantial fraction of Cd variance in finished chocolate products. Useful for teaching the agronomic-to-finished-product chain that drives observed contamination.
- App: Supports per-product-type and per-percent-cocoa risk profiles in chocolate-containing finished products. Cocoa-powder ingredients flagged at higher risk than cocoa-butter (which carries the fat fraction with little Cd) and at much higher risk than milk-chocolate finished products.