Overview
Adams et al. tested four Nigerian spice products for genotoxicity, microbial load, proximate composition, and heavy-metal content. The heavy-metal table is direct spice occurrence evidence for cadmium and nickel in curry, thyme, suya spice, and pepper-soup spice, with lead reported as not detected in all four products. Pepper-soup spice was the only product with detectable chromium.
Key numbers
All heavy-metal values in Table 5 are reported in mg/kg spice.
| Spice | Pb | Cd | Cr | Ni |
|---|---|---|---|---|
| Curry | ND | 0.657 | ND | 1.085 |
| Thyme | ND | 0.314 | ND | 1.142 |
| Suya spice | ND | 0.256 | ND | 3.258 |
| Pepper-soup spice | ND | 0.478 | 0.188 | 1.164 |
The paper lists standard-limit comparator values of 5.0 mg/kg for lead (Pb), 0.20 mg/kg for cadmium (Cd), and 1.63 mg/kg for nickel (Ni). The authors state that all four spices had cadmium above the cited standard limit and that only suya spice had nickel above the cited standard limit. The reported p-value row in Table 5 is 0.222 for Cd and 0.199 for Ni. The discussion states the cadmium and nickel limits as 0.02 mg/kg and 0.163 mg/kg, gives a cadmium mean of 0.426 mg/kg, and cites suya-spice nickel as 3.223 mg/kg. This page follows Table 5.
Methods (brief)
The spice samples were ashed, dissolved with concentrated nitric acid, evaporated to dryness, digested with hydrochloric acid, filtered hot through Whatman No. 4 paper, and made up to 100 mL. Minerals were determined by flame atomic absorption spectrometry (FAAS) with a hollow-cathode lamp and a fuel-rich flame. The paper does not report LOD/LOQ values for the heavy-metal table, so non-detects should remain source-level ND values rather than zeroes.
Implications
Certification: This source contributes occurrence evidence for Cd and Ni in mixed spice products from Nigeria, with a single chromium (Cr) detection in pepper-soup spice and Pb not detected across the four sampled products.
Courses: The paper is useful for teaching that informal or culturally specific spice mixtures can differ from standardized packaged spices in microbial and metal findings.
App: Broad spice-category routing is appropriate; the paper does not provide enough brand-neutral commodity detail to assign all findings to individual ingredient pages.
Microbiome (if applicable): The paper reports microbial counts for suya and pepper-soup spices, but it does not study human or food-system microbiome effects.
Related evidence
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