Whether you enjoy an aromatic bar with notes of caramel or something less fancy, chocolate can have many tastes. Now researchers say they have shed fresh light on a key ingredient that could open the door to new flavours.

They claim to have unpicked how and why the bacteria and fungi involved in the fermentation of cocoa beans influence the flavour of chocolate.

“We understand now what microbes we need and what they’re doing. And I think that opens up the opportunity … to be a lot more directed [about] how we make our chocolate in terms of its flavour.” said Prof David Salt, co-author of the work from the University of Nottingham.

Writing in the journal Nature Microbiology, the team report how they studied beans fermented at cocoa farms in three different regions of Colombia – Santander, Huila and Antioquia.

The researchers found that while the fermentation process was similar for the Santander and Huila farms, the beans at the Antioquia farm showed different temperature and pH patterns, which was most probably down to the presence and activity of a different group of microbes.

Further research revealed that while cocoa liquor made from the beans at Santander and Huila farms had fruity, floral, citrus notes – similar to the characteristics of a fine flavour cocoa from Madagascar – the cocoa liquor made from the beans at Antioquia lacked the fruity, floral, citrus flavours, in some ways resembling the liquor from fermented beans from the Ivory Coast and Ghana that are used in bulk chocolate production.

The team then used genetic sequencing to identify the microbes involved in cocoa bean fermentation from multiple sites in Colombia and beyond, explore the genes they contained, and hence identify the flavour substances they could produce during fermentation.

As a result, the researchers identified nine microbes that together were predicted to produce the notes of a fine flavour cocoa. They then introduced this community to sterile cocoa beans, and allowed them to ferment.

The upshot, said Salt, was a cocoa with floral, fruity and citrus notes and a recognisable cocoa flavour but with reduced astringency and bitterness.

“I call it the secret sauce,” said Salt.

He said the findings could have a number of applications, including helping cocoa farmers find ways to promote the presence of the key microbes during fermentation to ensure they can reproduce conditions required for high quality cocoa.

It could even help with the current crisis in the cost of chocolate, said Salt, suggesting that if cocoa farmers were able to produce more flavourful cocoa, less would be needed during production.

And there was another possibility.

“You could bring in either inoculums [of microbes] that could bring in particular flavours, new flavours that you just don’t see normally in cocoa,” he said. “Or you could actually come up with strategies to bias a fermentation, to come up with new flavours.”