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Cocoa bean processing can influence taste of chocolate

New research conducted on the Criollo and Trinitario varieties of noble cocoa revealed that different conditions during fermentation can affect the flavour of the finished fermented beans. The majority of the world’s cocoa production comes from the Forastero varietal, with more research carried out on the Forastero varietal than the Criollo and Trinitario varietals.

“Criollo cocoa is less bitter than Forastero, but is still more aromatic. You could call it the Pinot Noir of cocoa. But Criollo is a hassle to cultivate and it is difficult to grow in Africa, which is why it is grown in Central America, South America and Madagascar,” said Dennis Sandris Nielsen, a Professor at the Department of Food Science at the University of Copenhagen (UCPH FOOD).

A study carried out by the University of Copenhagen and researchers from Belgium and Nicaragua examined how changes in the fermentation process can affect the composition and activity of the microorganisms naturally present in the Criollo beans. This can affect the flavour of the fermented beans, as processing, including the fermentation and drying of the cocoa, can influence its overall quality.

“Our research confirms this and we have also learned how to fine-tune the cocoa by fine-tuning the process itself, which means that you can get a higher quality out of your raw materials if you understand these processes,” Sandris Nielsen said.

Researchers analysed fermentations from the highlands and lowlands of Nicaragua, alongside fermentations with a variety of oxygen availability. The research was conducted using a combination of high-throughput sequencing, chromatography and sensory analysis to understand the relationship between cocoa quality and processing.

“Our findings show that the treatment the cocoa receives after the harvest is at least as important for the quality and flavour as the genetics of the cocoa. Where the cocoa was grown also has some significance. By varying the conditions during fermentation, we can therefore also reasonably predict the final taste, which provides good opportunities for high-end producers in particular to develop chocolate with different flavours and scents,” Sandris Nielsen said.

A cocoa fruit contains 30–40 cocoa beans, surrounded by a pulp. In order to make chocolate from a raw cocoa bean, fermentation is needed to release its flavour potential.

The pulp inside the fruit is inoculated with various microorganisms from the surroundings and equipment it comes into contact with. This is because pulp is acidic (with a pH between 3 and 3.5) and has a high sugar content (10%), providing a harsh environment where only a few microorganisms can flourish. This process improves the fermentation of the cocoa beans, even if they are not inoculated with a starter culture, as there is a natural selection of microorganisms to positively affect the taste.

Yeast and lactic acid bacteria then grow, with the yeast forming alcohol, while the lactic acid bacteria eat the naturally present citric acid. The rising pH makes for a more favourable environment for acetic acid bacteria, converting the alcohol formed from fermentation into vinegar.

The alcohol and vinegar kill the germs in the cocoa beans, preventing them from germinating. Flavour development occurs when the cell walls are broken down, allowing different substances to react with each other, continuing as the beans are dried in the sun. The beans are dried until they are microbially stable, at which point cocoa farmers sell the fermented and dried beans to producers, who roast them to create the well-known and beloved flavour of cocoa.