The secret to the deep flavor of chocolate has been revealed. Researchers have discovered the microorganisms that determine the aroma and taste during the fermentation process of cacao seeds, the first step in chocolate production. Until now, the flavor varied depending on the climate and soil of the region where the cacao grew, but in the future, it will be possible to replicate the flavor of chocolate consistently anywhere in the world.
A research team led by Professor Gabriel Castrillo at the University of Nottingham in the U.K. noted on the 19th in the international journal "Nature Microbiology" that they confirmed a specific microorganism is closely linked to high-quality chocolate flavor during the cacao fermentation process.
The flavor of chocolate is determined by the fermentation that begins immediately after the cacao fruit is harvested. The fermented seeds of the cacao fruit are the raw material known as cocoa beans. Fermentation reduces bitterness and lays the foundation for a complex aroma and flavor.
Until now, harvested cacao fruits were piled up on the farm, allowing surrounding microorganisms to naturally intervene and carry out fermentation. Unlike methods such as adding specific microorganisms artificially, like in wine, cheese, or bread dough, the taste and quality of chocolate varied greatly depending on the harvesting period, farm, region, and country.
Researchers investigated three cacao farms in Colombia and confirmed that specific bacteria and fungi, along with their metabolic activities, play a crucial role in the deep flavor of chocolate at a farm in the Antioquia region. They also discovered that both abiotic factors like temperature and acidity (pH) and biotic factors such as microbial communities are important indicators of flavor expression.
The research team decoded the DNA of the microorganisms involved in cacao fruit fermentation to track their interactions and metabolic pathways. Based on this, they designed a customized fermentation microbial community composed of bacteria and fungi. Experiments using this community also replicated high-quality flavors, which were verified through tasters' evaluations and metabolite analysis.
Dr. David Gopaulchan, the first author of the paper, said, "We have demonstrated that chocolate producers can now predict flavors and achieve consistent quality through indicators such as pH, temperature, and changes in microorganisms," adding that it marks a turning point where fermentation, which was left to nature, is transformed into scientific management.
Dr. Gopaulchan also stated, "Just as the beer and cheese industries have innovated with starter cultures that induce fermentation, cacao fermentation is expected to enter a new era based on data, microorganisms, and flavor optimization."
The research team expressed expectations that they would advance this process to produce high-quality chocolate stably anywhere in the world and create new flavors in the future.
References
Nature Microbiology (2025), DOI: https://doi.org/10.1038/s41564-025-02077-6