Chocolate claims identified with a 'fingerprint'

Processing steps together with many other factors can affect a chocolate’s flavour and contribute to its unique chemical make-up. Chocolate ingredients are sourced from different regions of the world and this can affect the fermentation process, thereby influencing the flavour compounds in chocolate.

Traceability of cocoa is becoming more important for quality control in the chocolate industry, so that consumers can know they are purchasing products that adhere to fair-trade regulations, organic farming practices, etc. In order for consumers to be certain that the chocolate bar they have purchased is really from the exotic locale stated on the wrapper, researchers are now looking at a chemical ‘fingerprint’ method.

The method being developed can determine where a particular chocolate was produced — and someday, which farm its beans came from. The researchers are presenting their results through the American Chemical Society (ACS) SciMeetings online platform.

According to the project’s principal investigator, Shannon Stitzel, PhD, the idea originated from a lab experiment she ran during one of her courses.  “The method we used to analyse 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,” Stitzel said.

Early on, Stitzel’s experiments at Towson University 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, Stitzel wanted to go further and analyse 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.

Through a friend in the industry, Stitzel 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 finagled by nefarious producers.

Stitzel said that eventually their method could be used to help map out the expected flavour profiles of a chocolate, given its chemical signature. And she 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.

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