The study by researchers at Instituto de Cultivos Tropicales (ICT), the United States Department of Agriculture (USDA) and the University of Florida say the findings present a potential threat to Peru’s cocoa exports and a problem for chocolate quality.
Cadmium (Cd) levels in beans from most major growing regions in Peru were higher – and in some cases double - the EU’s planned max limits for chocolate and cocoa products, which enters force on January 1, 2019 (See Fact Box).
The study was published in the journal Science of the Total Environment.
Analyses of 70 plantations
The researchers analyzed cocoa leaves and beans in three major growing regions of Peru: North (regions of Tumbes, Piura, Cajamarca, and Amazonas); Center (regions of Huánuco and San Martin) and South (Junin and Cuzco).
They measured concentrations of heavy metals, including cadmium, lead, chromium, copper, manganese, nickel, iron and zinc in leaves and beans from 70 cocoa plantations, which were between 10 to 15 years old.
The researchers used the EU’s incoming regulation on cadmium limits for chocolate with more than 50% of cocoa solids (0.80 mg/kg) as its reference to evaluate cadmium levels found in beans and leaves on the farms.
Findings: Cadmium levels a concern
“Overall, concentrations of heavy metals were below the critical limits; however, the presence of high levels of Cd in cacao grown in the Amazonas, Piura and Tumbes regions is of primary concern,” wrote the researchers.
Cadmium concentrations in cocoa beans were above the 0.80 mg/kg threshold in Amazonas (0.97), Piura (1.55) and Tumbes (1.78).
Cadmium concentrations in beans from the other regions were lower, but all except Cuzco had beans with cadmium above 0.20 mg/kg, the EU’s incoming limit for milk chocolate with less than 30% cocoa solids.
Dr Silke Elwers, scientific consultant at ForestFinest Consulting, previously told this site that contaminants such as heavy metals and mycotoxins are so stable that you cannot get rid of them even during heat intensive processes such as cocoa roasting or chocolate processing.
The EU has set maximum levels for cadmium in foods since 2001. In 2014, it updated Regulation (EC) No 1881/2006 to add maximum thresholds for milk and dark chocolate. Previously it only had limits for certain meats, vegetables and seafood.
From January 1, 2019:
- Milk chocolate with below 30% total dry cocoa solids must contain no more than 0.10 mg/kg wet weight of cadmium.
- Chocolate with over 30% cocoa and below 50% must have no more than 0.30 mg/kg of cadmium.
- Chocolate with more than 50% will have a threshold of 0.80 mg/kg.
- Cocoa powder sold to the final consumer typically as drinking chocolate will have a limit of 0.60 mg/kg.
Limits are lower for chocolate varieties consumed by children.
The EU has set a TWI (tolerable weekly intake) limit for cadmium of 2.5 µg/kg body weight and says dietary exposure among European consumers is close to or exceeding the limit.
The European Commission said chocolate was an “important source of human exposure to cadmium”, along with seafood, oilseeds and edible offal, and highlighted that it was one of the top dietary sources of cadmium for children.
No limit values exist for cadmium in chocolate in the US. However, California requires a warning label on products that have more than 4.1 mg of cadmium per daily serving of a single product. Dr Elwers says this level is easily reached by some chocolates. The FDA has also set a guidance limit of 0.1 ppm for lead in candy consumed by young children.
The researchers suggested plantations must think carefully about the combination of tree types/clones used, as some combinations can accumulate higher levels of cadmium.
“Plantations of cacao with different cacao clones show differences in Cd accumulation both in leaves and cocoa beans.
"Therefore, it is promising to screen low Cd accumulator cacao genotypes for safe production of cacao on lightly to moderately Cd contaminated soils,” they said.
- Planted area: 107,000 hectares.
- Production: 82,000 metric tons a year.
- Accounts for only around 2% of world cocoa production.
- Second largest producer of organic cocoa, behind the Domician Republic.
CCN-51 is the main genotype in most Peruvian cocoa plantations.
[Source: Peru’s Ministry of Agriculture / Arévalo-Gardini et al.]
The researchers found higher cadmium levels in leaves and beans from the combination of the clones CCN51 and ICS95, compared to CCN-51 leaves and beans alone.
However, they found, when a plantation had a combination of clones CCN51, ICS95 and ICS39, accumulation in beans and leaves was lower.
“This implies that the combination of more clones may reduce Cd concentration in leaves and the rootstock could be an efficient alternative for preventing Cd accumulation in shoots,” they said.
The researchers added zinc may have a direct effect on cadmium accumulation in cacao.
Heavy metals can accumulate in plants through several factors such as the soil texture, pH levels and the plant genotype. Accumulation is believed to vary depending on plant species, according to the researchers.
Previous research from Bertoldi et al. has indicated higher levels of lead and cadmium in cocoa beans in Latin America compared to beans from West Africa.
The findings come as major chocolate companies in the US and Germany have been criticized for traces of carcinogens in end products. Mars, Hershey and others are also facing lawsuits for alleged cadmium and lead contamination in chocolate.
[Background reading....Killing at source: How to avoid cadmium and lead in chocolate]
Science of The Total Environment, Vol, 605–606, 15 December 2017, P 792–800
‘Heavy metal accumulation in leaves and beans of cacao (Theobroma cacao L.) in major cacao growing regions in Peru’
Authors: Enrique Arévalo-Gardini, Cesar O. Arévalo-Hernández, Virupax C. Baligar, Zhenli L. He