"This makes it possible to create a whole range of boutique chocolates to match everyone's favourite flavour, similar to wines, tea, and coffee," said Jan Steensels, a postdoctoral researcher at the University of Leuven, and the Flanders Institute for Biotechnology, Belgium.
Initially, the researchers sought robust yeast strains that could outcompete the many invading yeast strains that flood the 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, a postdoctoral researcher with Steensels at the two institutions.
But by outcompeting other microbes, robust yeast strains could prevent such infelicitous variability in taste, she said.
Researchers noted striking differences in aroma among the chocolates made from fermentations using different robust yeasts, said Steensels.
That was remarkable, he said, 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 flavor production.
The researchers hypothesise that the volatiles are protected from evaporation since they are dissolved in the fat fraction.
They combined two critical characteristics of yeast in single hybrid variants: the ability to dominate cocoa fermentations, and to produce a specific flavor.
"This means that for the first time, chocolate makers have a broad portfolio of different yeast strains that are all producing different flavors," said Steensels.
"This is similar to the current situation in beer brewing and wine making," he said.