Joyce et al. 2016 — Effects of cooking methods on heavy metals in fresh and smoked bush meat (Ghana)
This Ghanaian study measured six metals (Fe, Mn, Cu, Zn, Cd, Pb) in 35 bush-meat samples drawn from two commonly hunted species — cane rat (Thryonomys swinderianus) and giant rat — sold in three Ashanti Region markets, then compared concentrations across four cooking states (raw, boiled, fried, grilled) plus smoked and smoked-then-boiled processed meat. Lead was the dominant safety concern: fresh and boiled samples sat at multi-ppm concentrations well above the paper’s stated 0.01–0.38 ppm reference range, while grilling and smoking reduced lead concentrations substantially. Cadmium was reported as a single uniform value of 0.10 ppm across every cooking method, which the authors interpret as “unaffected by cooking” but which is consistent with the value sitting at or near the instrument’s reporting floor.
Key numbers
Source units are ppm (= mg/kg ≈ µg/g). For HMTc-relevant analytes the values below are the means reported in Table 1; the paper does not report standard deviations, detection limits, recoveries, or reference-material values.
Lead (Pb), bush-meat composite (cane rat + giant rat):
- Fresh: 4.31 ppm (= 4,310 µg/kg)
- Boiled: 13.93 ppm (Table 1); 13.73 ppm (text, page 2) — see verification note on internal discrepancy
- Fried: 17.32 ppm
- Grilled: 3.59 ppm
- Smoked (processed) fresh: 0.07 ppm
- Smoked (processed) then boiled: 0.05 ppm
- ANOVA p-value across cooking methods: 0.48 (not significant at p<0.05)
Cadmium (Cd):
- Identical 0.10 ppm reported for fresh, boiled, fried, grilled, smoked-fresh, smoked-boiled
- ANOVA p-value: 1.00 (no variance across groups)
Iron (Fe):
- Fresh 12.72; boiled 19.17; fried 5.61; grilled 26.06; smoked-fresh 15.28; smoked-boiled 16.41
- ANOVA p<0.01 (only metal with statistically significant cooking-method effect)
Manganese (Mn): fresh 5.16; boiled 0.64; fried 0.84; grilled 0.41; smoked-fresh 5.33; smoked-boiled 1.25; p=0.11.
Copper (Cu): fresh 0.96; boiled 1.09; fried 0.56; grilled 1.99; smoked-fresh 0.94; smoked-boiled 1.24; p=0.26.
Zinc (Zn): fresh 7.40; boiled 7.20; fried 7.64; grilled 6.97; smoked-fresh 7.39; smoked-boiled 6.66; p=0.39.
The authors compare these values against in-paper reference ranges (“safe limits”) of Fe 4.49–15.0, Cu 0.87–5.0, Zn 0.41–5.0, Cd 0.33, and Pb 0.01–0.38 ppm. No agency citations are given for these reference ranges and no Mn limit is stated.
n=35 total: 15 fresh cane rat, 15 fresh giant rat, 5 smoked (processed) cane rat. Sample weight 80–130 g each. Jurisdiction: Ghana (GH).
Methods (brief)
Bush-meat carcasses (cane rat Thryonomys swinderianus and giant rat) were purchased from three Ashanti Region markets. Muscle including bone was distributed across four cooking conditions: raw, boiled (in tap water on a gas stove until cooked), grilled (charcoal coal-pot with metal grids, 10–15 minutes), and fried (vegetable oil at 170 °C, 3–5 minutes after a 5–8 minute parboil). Smoked samples were obtained pre-smoked from the central market and analysed both as received and after boiling. Cooked samples were air-dried for 3–5 days and blender-milled. 1 g aliquots were nitric-acid digested in glass beakers on a stove, filtered to 50 mL with distilled water, and quantified for Fe, Zn, Cu, Mn, Pb, and Cd by atomic absorption spectrometry at the Ghana Atomic Energy Commission. Statistics: one-way ANOVA with Duncan’s multiple range test in SPSS v20 at p=0.05.
The paper does not report: instrument make or model, digestion conditions (temperature/time/acid concentration beyond “nitric acid”), reference material results, recovery percentages, instrument detection or quantification limits, replicate counts per group, or whether the reported values are means of replicates or of pooled samples.
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Verification notes
- Identity verified against the PDF at
raw/manual-fetch/seasonal-geographic-variance/auto-fetched/auto-game-meats-cd_2016_10-4172-2157-7110-1000617.pdf(sha256271331a32c509b8b5a18c356ee1395156cfe443f5a1fad6da9f1764c7e895d55). DOI 10.4172/2157-7110.1000617; J Food Process Technol Vol 7 Issue 9, article 617; received July 2016, accepted August 2016. - Internal Pb-boiled discrepancy: Table 1 records boiled Pb as 13.93 ppm. The Results narrative on page 2 reads “After boiling, it increased to 13.73 ppm and increased to 17.32 ppm after frying.” The 13.93 vs 13.73 difference is a single-digit transcription error in the narrative; Table 1 is treated as the authoritative figure on this page. Flagged here because the table-vs-text inconsistency was not corrected at proof.
- Cd uniformity: the paper reports Cd at exactly 0.10 ppm for all six cooking-state groups with p=1.00 and is silent on detection limits, replicate counts, and recoveries. A perfectly uniform mean across six groups with no variance is consistent with values sitting at the instrument’s reporting floor (and being rounded or reported as the floor) rather than with genuine biological constancy. Page values are reported as the authors state them; the QA-gap caveat is what the C-tier evidence rating reflects.
- Evidence tier C reflects the publishing venue (J Food Process Technol, OMICS open-access), the absence of any reported QA controls (no LOD/LOQ, no reference materials, no recoveries, no replicate structure), the small smoked-meat group (n=5), the unstated digestion details, and the Cd-uniformity reporting pattern. Findings are usable as occurrence data for cooked vs raw bush-meat Pb dynamics in Ghana but should not be pooled with A- or B-tier datasets.
- No brand names appear in the source; no brand-firewall edits required.
- Sampling year range left null: paper was received July 2016 but does not state the calendar year of sample collection.
- License: paper carries an explicit CC BY notice on page 1.
Page history
The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.
| Commit | Date | Description |
|---|---|---|
| 12d44c4 | 2026-05-29 | audit: eaglessmith2016-freshwater-fish-mercury-western-us-canada [revised] |