Heavy Metal Index
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Chemical and microbiological quality of commercial fresh and frozen chicken drumstick in Umuhia, Nigeria

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Overview

This study measured proximate quality, microbial counts, and selected heavy metals in fresh and frozen commercial chicken drumsticks sold in Umuahia, Nigeria. The occurrence data are usable for poultry-context routing, especially for frozen chicken drumstick values where several metals were higher than in fresh drumsticks.

Key numbers

Heavy metals were measured by graphite furnace AAS after acid digestion. Source units are mg/kg, reported on a fresh-weight (as-sampled) basis; the paper does not state the basis explicitly, but no drying step preceded digestion (a 2 g aliquot of meat was weighed directly into the digestion tube). Sample size was n = 20 per group (20 fresh and 20 frozen drumsticks, 40 total).

  • Fresh chicken drumsticks: Cd 0.019 +/- 0.007; Cr 0.029 +/- 0.015; Cu 0.067 +/- 0.022; Mn 0.390 +/- 0.272; Ni 0.577 +/- 0.300; Pb 0.024 +/- 0.006; Zn 0.825 +/- 0.269.
  • Frozen chicken drumsticks: Cd 0.094 +/- 0.077; Cr 0.047 +/- 0.017; Cu 0.117 +/- 0.027; Mn 0.117 +/- 0.040; Ni 0.852 +/- 0.456; Pb 0.074 +/- 0.034; Zn 0.828 +/- 0.457.
  • The authors cite comparator “toxic level” ranges of Cd 0.012-0.04, Cr 0.01-0.3, Cu 0.05-0.8, Mn 4.0-4.8, Ni 0.3-0.5, Pb 0.01-0.1, and Zn 5-40 mg/kg, attributed to NRC (1994), Nutrient Requirements of Poultry, 9th ed.

Methods

The drumstick samples (2 g aliquots) were digested in concentrated HNO3 at 135 degrees C until clear, then in a mixture of nitric acid (HNO3), perchloric acid (HClO4), and hydrogen peroxide (H2O2) in a 10:1:2 ratio for a further hour at 135 degrees C, with the cooled digest reconstituted in 1 M HNO3 and diluted to 25 mL. Cd, Cr, Cu, Mn, Ni, Zn, and Pb were quantified by graphite furnace atomic absorption spectrophotometry on a GBS Scientific Sens-AAS 1175 instrument. Chromium was measured as total Cr; no hexavalent speciation was attempted. Arsenic and mercury were not measured.

Implications

The source supports poultry-meat occurrence context for Nigerian market chicken. Frozen drumsticks carried higher mean Cd, Cr, Cu, Ni, and Pb than fresh drumsticks; Mn was the only metal lower in frozen samples than in fresh; Zn was statistically indistinguishable between the two formats. The values should not be generalized to all Nigerian poultry without preserving the fresh/frozen distinction.

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