Title
Mitigating the level of cadmium in cacao products: Reviewing the transfer of cadmium from soil to chocolate bar
Date Issued
10 August 2021
Access level
open access
Resource Type
review
Author(s)
Vanderschueren R.
Argüello D.
Blommaert H.
Montalvo D.
Maurice L.
Schreck E.
Schulin R.
Lewis C.
Vazquez J.L.
Umaharan P.
Chavez E.
Sarret G.
Smolders E.
University of Alberta
Publisher(s)
Elsevier B.V.
Abstract
The new EU regulation on cadmium (Cd) in cacao-derived products affects the cacao market worldwide. Here, we reviewed the journey of Cd from soil to chocolate bar and collated current data on the topic, giving due attention to data quality. Cacao bean Cd concentrations are typically about a factor two larger compared to the soil on which the cacao tree grows, this is high but not unusual and, therefore, the cacao plant is not classified as a Cd hyperaccumulator. Mean Cd concentrations in cacao beans range 0.02–12 mg Cd kg−1 and are markedly higher in Latin America, where more than half of cacao bean samples exceed the commonly applied threshold for export to the EU (0.60 mg kg−1). This regional enrichment is related to relatively high soil Cd concentrations in the young soils of Latin America. The source of Cd is, in general, likely geogenic rather than derived from phosphate fertilizers or contamination. A meta-analysis of 780 soil-plant paired data shows that soil Cd, soil pH and soil organic carbon largely explain cacao bean Cd concentrations. Detection of effects of cultivars, soil treatments or agronomic practices are strongly hampered by the spatial variability in phytoavailable soil Cd concentrations. Application of lime or biochar has the potential to lower bean Cd in acid soils. In the long-term, breeding low Cd cultivars likely provides the highest potential for mitigation but genetics and breeding research is currently limited by the lack of understanding of how Cd is loaded into the developing cacao fruit of this cauliflorous tree. Postharvest practices such as fermentation can slightly lower Cd concentrations in the final product but also play a large role in product quality. In the short term, mixing of cacao from different origins may be the most feasible strategy to meet the EU limits.
Volume
781
Language
English
OCDE Knowledge area
Agricultura Ciencia del suelo
Scopus EID
2-s2.0-85103696247
Source
Science of the Total Environment
ISSN of the container
00489697
Sponsor(s)
This work was financially supported by the Research Foundation Flanders (FWO-Vlaanderen), the French National Research Agency and the Belgian VLIR-UOS program . RV is the recipient of a predoctoral fellowship from FWO-Vlaanderen (FWO-SB). DA and JLV are working in the framework of the VLIR-UOS program “Food Standards for the Sustainability of the Cocoa Supply Chain” (TEAM-2017-01-62; EC2017TE441A101). HB works in the framework of the French National Research Agency program ‘Investissements d'avenir’ (ANR-15-IDEX-02), and in the CNRS/INSU/EC2CO project CACAO. HB and GS (ISTerre) are part of Labex OSUG (ANR10 LABX56). GS, HB and ES are working in the framework of the Program Hubert Curien “TOURNESOL” 2020–2021 (project n° 44274TC). FB, LM and ES (GET) would like to thank the French National Research Agency for the financial aid in the frame of the ANR-MONOIL Project N°ANR-13-SENV-0003-01. We express our gratitude to the farmers who allowed us to collect samples from their cacao crops. This document has been produced with the financial assistance of the European Union (Clima-LoCa ZKD9442 ). The contents of this document are the sole responsibility of ES and DM and can under no circumstances be regarded as reflecting the position of the European Union. The authors thank Dr. Anja Gramlich for sharing her research data so it could be included in the meta-analysis in this work. The authors also thank Dr. Matthias Wiggenhauser and Dr. Eline Blommaert for their assistance and input in the manuscript.
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