Arévalo-Gardini et al. 2017 — Heavy metal accumulation in cacao leaves and beans across Peru’s major growing regions
This study measured Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn in leaves and beans from 70 cacao plantations across three major Peruvian growing regions: North (Tumbes, Piura, Cajamarca, Amazonas), Center (Huánuco, San Martín), and South (Junín, Cuzco). The key finding is that more than 57% of all sampled cacao beans exceeded the EU critical limit of 0.8 µg/g (800 µg/kg) for Cd, with the Amazonas, Piura, and Tumbes regions being the primary drivers of exceedance. Genotype, soil Cd availability, and zinc-cadmium interactions were identified as significant determinants of accumulation, offering a path toward varietal and agronomic mitigation.
Key numbers
Cacao beans — mean Cd by region (µg/g dry weight):
- Tumbes: 1.78 ± 0.35; Piura: (values in exceedance range); Cajamarca: not separately tabulated; Amazonas: high (Amazonas, Piura, Tumbes cited as primary exceedance zones); San Martín: 1.00 ± 0.87; Huánuco: not tabulated separately; Junín: (lower); Cuzco: 0.17 ± 0.41
Mean Cd in beans range overall: 0.17 (Cuzco) to 1.78 µg/g (Tumbes) Mean Pb in beans: 1.00 ± 0.67 (Cajamarca/Cuzco) to 3.00 ± 1.39 µg/g (Piura) Mean Ni in beans: 3.5 ± 2.1 (Tumbes) to 9.25 ± 2.00 µg/g (Huánuco) Mean Zn in beans: 37.25 ± 2.70 (Huánuco) to 59.17 ± 1.56 µg/g (Piura)
Cacao leaves — mean Cd by region:
- Cuzco: 0.23 ± 0.62; Tumbes: 1.00 ± 0.87; Amazonas: 2.86 ± 0.31; Piura: highest overall
By genotype (beans):
- Native from Marañon: Cd 0.10 ± 0.9 µg/g (lowest)
- Spontaneous Hybrids: Cd 1.8 ± 0.4 µg/g (highest)
- CCN51: intermediate
EU critical limit for Cd in chocolate (≥50% cocoa solids): 0.8 µg/g — approximately 57% of all bean samples exceeded this threshold
Methods (brief)
AAS (Atomic Absorption Spectrophotometry; Varian Spectra 55B). Oven-dried leaf and bean samples (500 mg) digested with HNO₃ (65%) and HClO₄ (98%) 4:1 ratio on a block at 120°C then 200°C. Sampling conducted February–April 2014 across 70 plantations aged 10–15 years. Three repetitions per sample; means used for analysis. Statistical analysis in R v3.2; ANOVA and DGC test for regional differences.
Limitations
Study is dry-weight basis; does not report wet-weight equivalents or post-fermentation Cd concentrations, which are relevant for regulatory comparison (EU limits apply to processed beans). Baseline soil Cd data are discussed in a companion paper (Arévalo-Gardini et al. 2016), not this one. Short growing season sampled (dry season only). No iAs or tHg reported.
Implications
- Certification: Confirms that Peruvian-origin cacao, particularly from northern regions (Piura, Tumbes, Amazonas), carries Cd risk above EU and proposed HMT&C thresholds. Provides regional breakdown supporting geographic_breakdown entries for cocoa Cd.
- Courses: Central case study for how Cd accumulation varies by region and genotype within a single country — illustrates that “Peru cacao” is not a monolithic risk category.
- App: Supports regional risk differentiation for cocoa ingredient. Cuzco-origin cocoa is meaningfully lower risk than Amazonian/Piura-origin material. Flag for synthesis pass on cocoa Cd.