Overview
Tesfaye and Abebaw measured physico-chemical quality parameters and selected essential metals in four edible oil samples from the Ethiopian market. The metals table reports Cu, Zn, and Fe concentrations in mg/L after wet digestion and FAAS, with Na and K measured by flame photometry. This is not a toxic-metal occurrence paper for lead (Pb), cadmium (Cd), arsenic, or mercury, but it provides primary oil-matrix concentration data for copper, zinc, and iron in imported palm oil and Ethiopian nuog/niger seed oil.
Key numbers
Essential metals in edible oils
Table 5 reports mean +/- SD in mg/L. The original table uses commercial sample names; this source page relabels them by oil category and sample number to preserve the brand firewall.
| Category-level sample | Na (mg/L) | K (mg/L) | Cu (mg/L) | Zn (mg/L) | Fe (mg/L) |
|---|---|---|---|---|---|
| Imported palm oil A | 4.17 +/- 0.153 | 8.43 +/- 0.153 | 0.62 +/- 0.022 | 1.58 +/- 0.154 | 4.66 +/- 0.331 |
| Imported palm oil B | 4.10 +/- 0.100 | 8.27 +/- 0.209 | 0.28 +/- 0.004 | 1.27 +/- 0.255 | 6.51 +/- 0.193 |
| Ethiopian niger seed oil A | 3.80 +/- 0.100 | 8.10 +/- 0.200 | 0.86 +/- 0.003 | 1.19 +/- 0.160 | 7.32 +/- 0.530 |
| Ethiopian niger seed oil B | 4.13 +/- 0.153 | 10.30 +/- 0.200 | 0.42 +/- 0.005 | 1.47 +/- 0.567 | 6.08 +/- 0.818 |
The source states that the calibration curves for Na, K, Cu, Zn, and Fe had correlation coefficients from 0.9977 to 0.9999. Method detection limits were Na 0.0306 mg/L, K 0.0191 mg/L, Cu 0.0246 mg/L, Zn 0.0151 mg/L, and Fe 0.0283 mg/L. Limits of quantitation were Na 0.306 mg/L, K 0.191 mg/L, Cu 0.246 mg/L, Zn 0.033 mg/L, and Fe 0.075 mg/L.
Physico-chemical quality parameters
Table 1 reports mean +/- SD for four oil samples:
| Category-level sample | Acid value (mg KOH/g) | Saponification value (mg KOH/g) | Iodine value (g/100 g) | Peroxide value (meq/1000 g) | Moisture (%) |
|---|---|---|---|---|---|
| Imported palm oil A | 0.082 +/- 0.0047 | 189.80 +/- 3.528 | 97.545 +/- 0.6345 | 1.413 +/- 0.0808 | 0.163 +/- 0.0015 |
| Imported palm oil B | 0.091 +/- 0.0042 | 190.27 +/- 3.528 | 53.807 +/- 1.0150 | 1.233 +/- 0.0305 | 0.123 +/- 0.0046 |
| Ethiopian niger seed oil A | 0.276 +/- 0.0056 | 187.00 +/- 5.668 | 88.153 +/- 0.5300 | 0.893 +/- 0.0503 | 0.173 +/- 0.0015 |
| Ethiopian niger seed oil B | 0.188 +/- 0.0050 | 143.05 +/- 8.527 | 116.410 +/- 0.3863 | 1.460 +/- 0.0600 | 0.160 +/- 0.0010 |
The authors state that all acid values and peroxide values were within the FAO/WHO comparators they used, while the saponification value for one niger-seed-oil sample and the iodine value for one imported palm-oil sample and one niger-seed-oil sample were outside their cited comparator ranges.
Methods (brief)
The study selected two imported palm-oil samples and two Ethiopian processed nuog/niger-seed-oil samples from the Merkato commercial center. For metal analysis, triplicate 1 g oil samples were digested with concentrated nitric acid/hydrogen peroxide (2:1 v/v) plus sulfuric acid on a Kjeldahl digestion furnace at 250 C until clear. The solution was evaporated, redissolved in 0.2 M nitric acid, filtered, diluted to 50 mL, and analyzed for Cu, Zn, and Fe by flame atomic absorption spectroscopy. Sodium and potassium were measured by flame photometer.
The metal values are reported in mg/L in the diluted oil digest solution. The source does not report Pb, Cd, arsenic, mercury, nickel, aluminum, chromium, or tin.
Implications
Certification: This source is not a primary source for the HMTc toxic-metal analytes, but it provides edible-oil matrix context for Cu, Zn, and Fe in Ethiopia-market palm oil and niger seed oil. Do not use it as evidence of absence for Pb, Cd, arsenic, or mercury.
Courses: Useful for showing the difference between oil quality parameters and contaminant occurrence: the paper combines acid, peroxide, iodine, and saponification values with essential-metal measurements.
App: Adds category-level essential-metal context for palm oil and niger seed oil. Brand names from the source should remain excluded.
Microbiome: Not addressed.
Related evidence
- Copper
- Zinc
- Iron
- Palm oil
- Niger seed oil
- Vegetable Oils
- Vegetable Oils
- Other cooking oils (canola, sunflower, coconut, avocado, sesame)
Update history
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