Overview
Berego and colleagues measured essential and toxic metals in coffee beans and associated agricultural soils from Dale Woreda in Sidama, Ethiopia. The coffee-bean tables report lead (Pb), cadmium (Cd), chromium (Cr), and Co as not detected in both farm and washing-plant beans, while nickel (Ni), Cu, Zn, Mn, Na, K, and Ca were quantifiable at low mg/kg levels. Soil Cd exceeded the authors’ cited agricultural-soil comparator, so this source is useful for both coffee occurrence routing and supply-chain soil context without treating the soil values as coffee-product concentrations.
Key numbers
For farmer-farm coffee beans, Table 4 reports K from 69.06 +/- 0.047 to 99.93 +/- 0.037 mg/kg, Ca from 3.05 +/- 0.04 to 17.23 +/- 0.36 mg/kg, Na from 3.10 +/- 0.10 to 22.04 +/- 0.042 mg/kg, and Mn from 0.082 +/- 0.003 to 0.927 +/- 0.004 mg/kg.
For farmer-farm coffee beans, Table 5 reports Ni from 0.052 +/- 0.005 to 0.074 +/- 0.003 mg/kg, Zn from 0.055 +/- 0.004 to 0.073 +/- 0.003 mg/kg, and Cu from 0.14 +/- 0.0020 to 0.28 +/- 0.0037 mg/kg. Co, Cr, Pb, and Cd were not detected in every farmer-farm bean row.
For coffee-washing-plant beans, Table 7 reports Ca from 2.81 +/- 0.017 to 4.33 +/- 0.035 mg/kg, Cu from 0.146 +/- 0.004 to 0.277 +/- 0.011 mg/kg, K from 61.39 +/- 0.026 to 77.93 +/- 0.115 mg/kg, Mn from 0.08 +/- 0.003 to 0.92 +/- 0.001 mg/kg, Na from 1.43 +/- 0.035 to 15.04 +/- 0.041 mg/kg, Ni from 0.052 +/- 0.001 to 0.074 +/- 0.003 mg/kg, and Zn from 0.053 +/- 0.002 to 0.094 +/- 0.004 mg/kg. Cd and Co were not detected in all six washing-plant bean rows; the authors also state that Cr, Pb, and Cd were not detected in washing-plant beans.
Table 8 summarizes the product-facing ranges as farmer-farm coffee beans: Ni 0.05-0.08 mg/kg, Zn 0.054-0.076 mg/kg, Cu 0.14-0.29 mg/kg, Cr ND, Pb ND, and Cd ND; washing-industry coffee beans: Ni 0.05-0.08 mg/kg, Zn 0.051-0.09 mg/kg, Cu 0.14-0.28 mg/kg, Cr ND, Pb ND, and Cd ND.
Soil results are supply-chain context rather than product occurrence. The authors report Cd in soil above the 3 mg/kg permissible limit they cite for agricultural soils, while Pb and Cr were not detected in all soil samples.
Methods (brief)
Coffee beans were digested in a microwave system with nitric acid and hydrogen peroxide, and soil samples were digested using a modified EPA 3050B acid-digestion method. Metals were measured by flame atomic absorption spectrometry and flame emission atomic spectroscopy. The paper reports triplicate analytical replicates for the coffee-bean concentration tables.
Related evidence
- Coffee
- Coffee
- Cadmium
- Lead
- Chromium
- Nickel
- Copper
- Zinc
- Manganese
- Soil-to-plant transfer of heavy metals
Update history
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