Why premium chocolates taste flavourful

The findings were detailed in the study, ‘A defined microbial community reproduces attributes of fine flavour chocolate fermentation’, which was published in the journal Nature Microbiology on Monday (August 18). The study was conducted by researchers based at the University of Nottingham (United Kingdom), the University of the West Indies (Trinidad & Tobago), and the University of the Andes (Colombia).

The fermentation process

The quality and flavour profile of chocolate depend on cocoa beans, which are influenced by several pre- and post-harvest factors. One significant step in flavour enhancement is fermentation. Farmers first scoop out the seeds and pulp from the fruits of cacao trees. They then place the seeds, now called “beans”, in wooden boxes, covered with banana leaves to regulate environmental temperatures. This allows microbes to come from the surrounding environment and ferment the beans.

David Gopaulchan, a researcher at the University of Nottingham and lead author of the new study, told Scientific American, “If you skip this process, your beans don’t taste much like anything; they taste more like plants. So the fermentation is super important in the development of flavour precursors.”

Unlike in the case of wine, cheese, and beer, the fermentation of cocoa beans is a natural process that typically takes place without adding specific microbes. “It’s totally spontaneous and uncontrolled. It’s whatever microbes exist at the farm,” Gopaulchan said.

As a result, the taste of beans varies widely depending on harvests, farms, regions, and countries. While most of the beans produced globally go into bulk chocolate, which usually has a basic, bittersweet taste, a small percentage of them go into premium chocolate, which has a distinct flavour profile.

Gopaulchan said, “My home country, Trinidad, is known for chocolates that taste like wine, but other regions like Venezuela are known for having very nutty flavour profiles in their beans.”

The new study

As cocoa fermentation is a natural process, scientists until now knew little about what kind of microbes and conditions influenced the taste of chocolate.

To resolve the mystery, Gopaulchan and his colleagues took samples of fermenting beans from different cocoa farms in Colombia. By analysing genetic material in the samples, they found five bacteria and four fungi that were consistently found in batches of beans that produced premium chocolate.

The researchers then took cocoa beans that were sterilised to ensure no other microbes were on them. Next, they used the nine microbes to ferment these beans before grinding them into a liquid, called cocoa liquor.

It was found that the microbes added citrusy flavours, berry flavours, flowery flavours, tropical fruit and caramel flavours to the cocoa liquor.

The significance

The researchers have said their findings indicate that adding the nine microbes to fermentation mixtures could help cocoa growers improve the flavour of their cocoa. This could increase the value of cocoa.

David Salt, researcher at the University of Nottingham and co-author of the study, told New Scientist, “We don’t necessarily need to give them a sample of the nine microbes – there are almost certainly practical things they can do to bias their microbiome in the right direction. For instance, we could tell them that some of the fungi they need are on the outside of cocoa pods, so why don’t you whack a bit of the outside of a pod in there?”