Yeasts used to ferment cocoa during chocolate production can modify the aroma of the chocolate, resulting in a new era of boutique chocolates, Belgian researchers have said.

"The discovery makes it possible to create a whole range of boutique chocolates to match everyone's favourite flavour — similar to wine, tea, and coffee," said Jan Steensels, post-doctoral researcher at the University of Leuven and the Flanders Institute for Biotechnology, Belgium.

Initially, the researchers sought robust yeast strains that could out-compete the many invading yeast strains that flood cocoa beans during fermentation.

"After harvesting, the cocoa beans are collected in large plastic boxes, or even piled in large heaps on the soil, right in the farms where they are grown," said Esther Meersman, post-doctoral researcher with Steensels at the two institutions.

But they noted striking differences in aroma among chocolates made from fermentation using different robust yeasts.

That was remarkable since only the yeast strains were different.

The fermentations were performed identically, and the same recipe was used each time.

The team set out to breed novel yeast hybrids that would combine robustness with strong flavour production.

The investigators who collaborated in this research with Barry Callebaut, the world's largest chocolate producer, have combined two critical characteristics of yeast in single hybrid variants.

"This means that for the first time, chocolate makers have a broad portfolio of different yeast strains that are all producing different flavours," said Steensels.

"This is similar to the current situation in beer brewing and wine making. A new era of chocolate may be dawning," noted the research team.

The paper is published in the journal Applied and Environmental Microbiology.