Life Science

Scientists create ancestry test for your chocolate bar

DNA barcoding could eventually help improve dangerous conditions for cocoa growers

December 24, 2021
Cocoa farmer holds dried cocoa beans
Using cocoa bean DNA to create unique identifiers, like fingerprints, can help track products in a complicated supply chain. [Credit: Irene Scott/Flickr | CC BY 2.0]

Chocolate may be a sweet treat, but it’s part of a $200 billion-plus global industry that does not want to face a bitter truth: no one can say exactly where many of its products come from. 

That’s a big problem because child labor, deforestation and other exploitative practices are common on cocoa plantations, including millions of small farms in West Africa that supply most of the world’s cocoa beans, the key ingredient of chocolate. While big manufacturers like Nestlé claim their products are ethically sourced, the lack of reliable digital tracking along a complex supply chain makes it almost impossible to test their claims.

Now, some researchers based in the U.K. think they have a solution: tracking beans using their genetic information. “You need to find what is immutable and what is something that no one can change,” says one of them, Pedro Lafargue, who has a doctorate in genetics and supply chain technology from the University of the West of England. That something is DNA, as Lafargue and his co-authors explain in a study published recently in the journal Supply Chain Management. 

With the help of a blockchain — usually associated with Bitcoin, it is a list shared with different owners along a supply chain that is difficult to change without permission — which protects the tag from being tampered with, a DNA-based tagging system would be more reliable than current systems that depend on physical barcoded tags, asserts Lafargue, who now works for a major cocoa supplier Olam International

To test their idea, the team used genetic data from one of the world’s largest repositories of cocoa DNA to trace Kit Kat and Mars bars from a candy shop in Britain all the way back to cocoa trees in the Ivory Coast.

DNA barcoding is essentially an ancestry test for cocoa, capable of tracking the genes of selected cocoa beans or trees in a region from farm to table, explains Lafargue. Current tagging systems are not accurate because crops are mixed at multiple stops along the cocoa supply chain which could lead to error and cheating, says co-author Glenn Parry in a YouTube video about the project. Because no one can identify where the cocoa comes from, traders, for example, are free to claim that a bag of cocoa contains only one kind of cocoa when there’s actually a mix, which can affect the quality of products made down the line. 

At a time when advocacy groups are shining a light on child labor, deforestation and other harmful practices, a DNA barcoding system would allow them to fact-check chocolate companies’ claims that their beans don’t exploit workers, says Lafargue. But first, he adds that they will need to build up a digital “library” of genetic barcodes. Auditors trained on the equipment would need to visit the plantations, take leaf samples and enter them into a global genetic database.

Once the system is in place, analyzing chocolate samples and checking the DNA against the digital library is cheaper and faster than other methods, according to Parry, who is a professor of digital business at the University of Surrey. Typically, it takes just two weeks and costs less than $7 per sample, compared to the traditional lab analysis method which can take months and cost $60 per sample. 

If scaled up sufficiently, these databases could make a real difference in improving conditions on plantations, according to one advocate. “It becomes a lot harder for big companies to claim ignorance if we have tools that actually say we know where [cocoa] comes from,” says Antonie Fountain, managing director of the VOICE network, an industry watchdog based in the Netherlands.

Other kinds of technology can also help monitor what is really happening on cocoa farms, says Fountain, including LIDAR, or Light Detection and Ranging, a remote sensing method that uses a laser to produce 3D information about the Earth’s surface and can penetrate forest cover. This is useful since cocoa farms are less than 5 acres or equivalent to four football fields. But he asserts that no technology will be a “magic bullet” that eliminates exploitative labor and environmental practices. With an estimated 4.5 million cocoa farms worldwide, the system will still depend largely on self-reporting by growers, adds Fountain.

Ranjana Bhattacharjee agrees. A molecular geneticist and breeder at the Nigeria-based International Institute of Tropical Agriculture, she focuses on sustainable cocoa cultivation. She explains that many West African farmers are victimized by theft and poverty due to fluctuating cocoa prices as well as poor health due to unsafe working conditions. For the majority of farmers, child labor is one way to squeeze out some additional income, she says. 

“How can you blame that person when he puts his children on the farm?” Bhattacharjee asks. 

For cocoa DNA barcoding to work, she says, researchers and breeders would not only need to collect data on the ground, but they would also need to maintain the database to ensure it is secured and up to date. That is no small task, but Bhattacharjee thinks it can be done — if chocolate companies are sufficiently committed. 

“I think we have enough human resources to do this work and we can do it well,” she says.

Correction: A previous version of the article stated that the researchers were British. It is more accurate to say they are based in the U.K.

About the Author

Deborah Balthazar

Deborah Balthazar is a science writer based in the New York Area. She’s a New Jersey native and has previously worked as a local government reporter for When not writing, she enjoys sleeping, reading, crocheting, and watching TV with her parents.



I found this article of interest.I am a cocoa grower in Trinidad.. The issue of child labor on covoa farms .is not a concern in Trinidad .Farmers are encouraged to use sustainable organic agro farming practices to produce quality fine flavour beans.

Dear Deborah, lovely to read your article and very honored to be part of this ground breaking technologies. I haven’t had the pleasure to meet Ranjana, but I am please to know that we agreed on the principals of scaling up this technology. The new traceability policies are coming into place and we need to identify funding bodies or governmental agencies that are willing to support and invest in this project.

Dont hesitate in reaching out again,
Have a great start of 2022!

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