“The chemical fingerprint of chocolate”: Researchers map authenticity of cocoa beans

21 Apr 2020 --- US researchers are developing a precision authentication testing method to determine “without any doubt” the chocolate’s country of origin to ensure that it has not been adulterated with inferior ingredients and is as sustainable as the label suggests. Chocolate ecology is a vital step that helps manufacturers determine what to put on-pack to appeal to conscious consumers looking for organic, fairtrade and certified products. However, this can be tricky as many factors can affect a chocolate’s flavor, including processing, and contribute to its unique chemical make-up.

FoodIngredientsFirst speaks with Shannon Stitzel, Ph.D., the project’s principal investigator, who explains how the drive behind this work is to add to the traceability toolbox available. This, in turn, helps identify a cocoa sample’s place of origin and may potentially pinpoint the specific farm where a chocolate’s beans were grown.

The flavor and aroma of a chocolate product emerges from its ecology, in addition to its processing.

“Some companies are sourcing directly from local farmers and know exactly where and from whom they are purchasing their cocoa. But other companies are not able to trace back the points of origin for all of the cocoa they’ve used, and this can be a problem for a variety of reasons,” she explains.

Click to EnlargeInnovators are tapping into the growing single-origin trend, which is among the most notable trends in chocolate. Cleaning up the supply chain
There has been a movement within the cocoa supply chain in recent years to clean up the industry by ensuring sustainable practices, transparency, traceability as well as weed out any child labor issues that have – and still do in some cases – blight the industry. Key plays such as Mars, Nestlé and Hershey pledged many years ago to stop using cocoa harvested by children and many suppliers have been working hard to eradicate these types of issues from their supply chains. 

However, the total eradication of child labor remains a major challenge for the industry, particularly as around two-thirds of the world’s cocoa supply comes from West Africa. 

Additionally, the quality, sustainability and source of cocoa has become more pronounced as innovators tap into the growing single-origin trend, which is among the most notable trends in chocolate. Single-origin chocolate is linked with premiumization as consumers are looking for more authenticity and are willing to pay a higher price for it. 

“Ultimately, consumers will pay more for products if they are certified as meeting particular preferential standards, such as fair trade, organic or not using child labor. Provenance is highly correlated to some of these standards, and chemical signatures can help verify provenance as a stand-alone tool or be used as an additional validation to support other traceability processes. Chemical signatures are harder to fake, and so potentially are a good mechanism to facilitate transparency in the cocoa supply chain,” Dr. Stitzel adds. 

The researchers are presenting their results through the American Chemical Society (ACS) SciMeetings online platform.

“The project originated out of an idea I had for a lab in one of the courses I teach,” Dr. Stitzel, further explains. “The method we used to analyze chocolate bars from a grocery store worked well in the class, and the exercise piqued the students’ curiosity. So, I started reaching out for more interesting samples and tweaking the technique.” 

Click to EnlargeThe genes of the tree the pods are harvested from, as well as the environment the tree is grown in, can affect the composition of the final product. The constituents behind the flavor
The process of making chocolate begins with the pods of the cacao tree. The genes of the tree the pods are harvested from, as well as the environment the tree is grown in, can affect the composition of the final product. 

Processing steps can also change a chocolate’s complex chemistry. Generally, after cocoa beans obtained from the pods have been fermented, dried and roasted, they are ground into a paste, called cocoa liquor, which contains cocoa solids and cocoa butter. Sugar and other ingredients are added to the liquor to make chocolate. 

Any of these steps could be varied slightly by the company performing them, leading to differences in chocolate composition. Even more variation between chocolates from different regions can come from naturally occurring yeast in the pods that surround the beans, which can affect the fermentation process, thereby influencing the flavor compounds in chocolate. 

Stitzel’s initial experiments at Towson University, Maryland, US, involved a well-known method for geographic determination. She used elemental analysis, which has been used to identify the source of a myriad of unknown materials. However, she wanted to go further and analyze the organic compounds in cocoa liquor to see if any of them remained after various processing steps. If so, they could be used as markers for more precise authentication testing. She acquired single-source samples of cocoa liquor from all over the world. Her undergraduate student, Gabrielle Lembo, used liquid chromatography (LC) to separate the cocoa liquor compounds from various samples and mass spectrometry (MS) to identify their chemical signatures. Lembo’s results showed that LC-MS is a robust analysis technique. Compounds, such as caffeine, theobromine and catechins, are detected in different patterns that make up a signature “fingerprint.” This fingerprint indicates provenance and cannot easily be manipulated by nefarious producers. 

Stitzel says that eventually their method could be used to help map out the expected flavor profiles of a chocolate, given its chemical signature. She also says it would be interesting to first determine the fingerprint of a cocoa bean, then gather fingerprints with each consecutive processing step to see how they change. For now, her students are expanding the application of the analysis method by looking at the chemical signatures of various forms of fair-trade and organic coffee. 

“Right now we can identify the country of origin. The next steps are to hopefully obtain samples from regions within a country, to see how narrowly we can determine provenance,” Dr. Stitzel concludes. 

By Gaynor Selby

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