Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. 
Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. What was studied?
This original study traced cadmium in cacao from soil to chocolate on a single Colombian farm to identify critical control points that matter for compliance with regulatory limits and heavy metal certification. By quantifying cadmium (Cd) in soils, fertilizers, fresh seeds, fermented and dried beans, nibs, shells, and finished chocolate, the authors examined how soil chemistry (pH 4.7–4.9; SOM 2.93–3.78%; high assimilable P) and post-harvest processing shape Cd levels in the final product. The work also evaluated whether more acidic, controlled fermentations alter Cd in beans.
What was studied?
This original study traced cadmium in cacao from soil to chocolate on a single Colombian farm to identify critical control points that matter for compliance with regulatory limits and heavy metal certification. By quantifying cadmium (Cd) in soils, fertilizers, fresh seeds, fermented and dried beans, nibs, shells, and finished chocolate, the authors examined how soil chemistry (pH 4.7–4.9; SOM 2.93–3.78%; high assimilable P) and post-harvest processing shape Cd levels in the final product. The work also evaluated whether more acidic, controlled fermentations alter Cd in beans.
Most important findings
| Critical point for HTMC | Details relevant to certification and regulation |
|---|---|
| Soil is the dominant source of product Cd | Pseudo-total soil Cd averaged ~3.5 mg/kg with highest values in A–B horizons; acidic pH (4.7–4.9) and measurable SOM increased Cd availability, consistent with elevated bean Cd risk. The table on page 9 (Table 2) links horizons, pH, SOM, and P. |
| Fertilizers varied in Cd but were within EU limits | Six of 13 P fertilizers contained 3–30 mg/kg Cd, yet all were under the EU 60 mg/kg Cd in P₂O₅ threshold. Given farm inputs and buffering, fertilizers were not the primary driver of bean Cd at this site. |
| Fermentation and drying did not lower bean Cd | Across spontaneous and controlled acidic fermentations, bean Cd remained statistically unchanged (p>0.05), despite pH dropping to ~4.0–4.5 in TUCC (see page 10, Figure 4). Solar drying likewise had no effect. |
| Shells concentrate Cd; nibs are lower | Dehulling split Cd between shell and nib: shell ~6.57 mg/kg vs nib ~3.28 mg/kg, a significant reduction upon shell removal (p<0.05). Roasting did not change Cd. This aligns with shell cellulose binding vs fat-rich nibs carrying little Cd. |
| Chocolate Cd scales with % cocoa solids | The regulatory context is stringent for high-cocoa bars |
| Measuring “bean” vs “nib” changes outcomes | Whole-bean Cd can overstate product risk by ~20–40% compared with nibs/cocoa mass. The authors recommend testing nibs or liquor for trade decisions to avoid false failures. |
| Spatial heterogeneity matters | Subsoil Cd was patchy, linked to rock fragments and otavite in the C horizon; localized hotspots can drive exceedances even within one farm, highlighting the need for targeted soil mapping. |
| Leaf litter recycles Cd | Leaf litter (~0.3 mg/kg Cd) may retain Cd in the system, slowly returning bioavailable Cd to surface horizons and sustaining uptake pressure. |
| Regulatory context is stringent for high-cocoa bars | EU limits range from 0.10 mg/kg (milk, <30% cocoa) to 0.8 mg/kg (≥50% cocoa solids). Bars made from high-Cd nibs can exceed thresholds without upstream mitigation. |
Key implications
For HTMC, the primary regulatory impacts center on soil-driven Cd loading, making pH management and horizon-aware soil mapping decisive. Certification requirements should prioritize nib or liquor testing over whole beans and enforce shell removal efficacy verification. Industry applications include recipe optimization by cocoa-mass percentage and supplier screening by soil indices. Research gaps include cultivar physiology, endophytes, and microbial/chemical post-harvest chelation. Practical recommendations are to lime or amend soils to raise pH, winnow thoroughly, formulate lower-cocoa bars from high-risk lots, and standardize nib-based Cd analytics.
Citation
Bravo D, Santander M, Rodríguez J, Escobar S, Ramtahal G, Atkinson R. (2022). ‘From soil to chocolate bar’: identifying critical steps in the journey of cadmium in a Colombian cacao plantation. Food Additives & Contaminants: Part A, 39(5), 949–963. doi.org/10.1080/19440049.2022.2040747
Cadmium is a persistent heavy metal that accumulates in kidneys and bones. Dietary sources include cereals, cocoa, shellfish and vegetables, while smokers and industrial workers receive higher exposures. Studies link cadmium to kidney dysfunction, bone fractures and cancer.
