Chang et al. 2022 - Rhizobium treatment and cadmium in fermented cocoa
Chang and colleagues tested whether adding Rhizobium japonicum during fermentation reduced cadmium in two cocoa varieties, Nacional and Trinitarian. The study reports cadmium concentrations for six variety-by-treatment combinations after fermentation. The paper is intervention evidence for cocoa processing/fermentation rather than finished chocolate retail occurrence evidence.
Key numbers
Table 16 reports cadmium concentrations in cocoa after fermentation.
| Variety | Rhizobium japonicum induction | Cd |
|---|---|---|
| Nacional | 0% | 0.36 mg/kg |
| Nacional | 3% | 0.34 mg/kg |
| Nacional | 5% | 0.35 mg/kg |
| Trinitarian | 0% | 0.36 mg/kg |
| Trinitarian | 3% | 0.30 mg/kg |
| Trinitarian | 5% | 0.29 mg/kg |
The lowest reported value was 0.29 mg/kg in Trinitarian cocoa with 5% Rhizobium japonicum induction. The two untreated controls were both 0.36 mg/kg. The abstract describes a reduction “from 36 to 29 mg/kg (ppm),” but Table 16 reports 0.36 to 0.29 mg/kg.
Methods (brief)
The study used a completely randomized bifactorial design with three replications. Treatments combined two cocoa varieties, Nacional and Trinitarian, with Rhizobium japonicum induction at 0%, 3%, and 5% per two kilograms of fermentative mass. During fermentation the authors tracked pH, degrees Brix, and temperature; after fermentation, beans were sun dried for six days and evaluated by cut test and sensory analysis. Cadmium was measured by atomic absorption. No lead, arsenic, mercury, nickel, chromium, tin, aluminum, or uranium values are reported.
Implications
Certification: The source provides Ecuador cocoa cadmium intervention data, not a market benchmark distribution. The values are treatment means and should not be pooled as independent retail chocolate samples.
Courses: Useful for explaining the difference between occurrence surveillance and mitigation studies: this paper can inform processing hypotheses but does not replace market sampling.
App: Adds context for cocoa cadmium mitigation and flags Rhizobium-treated fermentation as an intervention claim that would need direct lot testing before product-level use.
Microbiome: The study uses a microbial inoculant during fermentation, but it does not address human or gut microbiome effects.
Wiki pages this source may touch
Verification notes
The PDF title, byline, citation block, DOI, journal, treatment table, and methods were read from the source PDF. The abstract’s “36 to 29 mg/kg” statement appears inconsistent with Table 16’s 0.36 to 0.29 mg/kg values; this page uses Table 16 as the extraction basis and records the discrepancy.
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 |
|---|---|---|
| 2c492a7 | 2026-06-03 | ingest auto-fetched 2026-06-03: aburas2023-libyan-honey-lead-cadmium |