Okeke and Sanda 2026 - Metals in calcium-carbide-ripened fruits
Okeke and Sanda measured chromium, lead, and total arsenic in banana, pineapple, and orange after natural ripening and after laboratory calcium-carbide ripening. All measured values were below the paper’s cited FAO limits, but the calcium-carbide-ripened fruits had higher Cr, Pb, and As than their naturally ripened counterparts.
Key numbers
Table 1 reports fruit metal concentrations in mg/kg. The paper labels the arsenic column as As and uses total digestion/AAS rather than arsenic speciation, so these values are treated as total arsenic.
| Fruit and ripening condition | Cr (mg/kg) | Pb (mg/kg) | tAs (mg/kg) |
|---|---|---|---|
| Banana, naturally ripened | 0.001 +/- 0.01 | 0.001 +/- 0.01 | 0.001 +/- 0.01 |
| Pineapple, naturally ripened | 0.002 +/- 0.01 | 0.001 +/- 0.01 | 0.002 +/- 0.01 |
| Orange, naturally ripened | 0.009 +/- 0.03 | 0.001 +/- 0.02 | 0.003 +/- 0.01 |
| Banana, calcium-carbide ripened | 0.003 +/- 0.01 | 0.004 +/- 0.01 | 0.003 +/- 0.01 |
| Pineapple, calcium-carbide ripened | 0.006 +/- 0.03 | 0.003 +/- 0.01 | 0.004 +/- 0.01 |
| Orange, calcium-carbide ripened | 0.014 +/- 0.06 | 0.002 +/- 0.01 | 0.006 +/- 0.03 |
The authors cite FAO limits of 0.5 mg/kg for Cr, 0.2 mg/kg for Pb, and 0.5 mg/kg for As. The highest reported values in this study were 0.014 mg/kg Cr in artificially ripened orange, 0.004 mg/kg Pb in artificially ripened banana, and 0.006 mg/kg tAs in artificially ripened orange.
For artificially ripened fruits, adult estimated daily intake values were reported as 2.2E-5 to 0.0001, depending on fruit and metal. Child EDI values were higher, ranging from 2.5E-5 to 0.0002. Hazard index values were below 1 for every fruit: adults 0.0115 for banana, 0.0111 for pineapple, and 0.0123 for orange; children 0.0200 for banana, 0.0191 for pineapple, and 0.0213 for orange.
Methods (brief)
Freshly unripe but mature pineapple, banana, and orange were purchased from three local markets in Bauchi Metropolis with assistance from fruit vendors. Fruits were divided into naturally ripened and artificially ripened groups; the artificial group was ripened with 10 g calcium carbide. Ripened fruit was washed with deionized water, peeled, sliced with a plastic knife, oven-dried at 70 degrees C for 48 h, ground, sieved, and stored in airtight plastic containers. One gram of each pulverized fruit sample was ashed at 550 degrees C for 6 h, dissolved in 10% HNO3, heated for 20 min, filtered, and analyzed in triplicate by atomic absorption spectrophotometry.
Implications
Certification: This is fresh-fruit occurrence evidence for Pb, Cr, and total arsenic, but it should be stratified by market and ripening treatment. Calcium-carbide treatment is an artificial post-harvest condition and should not be silently pooled with naturally ripened fruit.
Courses: Useful example for post-harvest chemical treatment as a contamination lever and for preserving total-arsenic rather than inorganic-arsenic labels.
App: Supports a qualitative note that artificial carbide ripening can increase measured metal residues in fruit, while the study’s absolute values remain low and Nigeria-specific.
Wiki pages this source may touch
Verification notes
This page was built from the PDF text, including the abstract, sample preparation, metal determination method, Table 1 fruit concentrations, Table 2 EDI/HQ values, Figure 1 hazard-index text, discussion, and conclusions. The paper sometimes writes “FOA” where FAO is evidently intended; this page preserves the cited numerical limits without treating them as independently verified regulatory values. Chromium is total chromium, not Cr(VI), and arsenic is total arsenic, not inorganic arsenic.
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 |
|---|---|---|
| 4039d20 | 2026-06-10 | scope: broaden ingest to the full upstream+downstream literature (marine, atmospheric, attribution, exposure, toxicology) — inclusion is the default |