In a finding that could lead to better, high quality chocolates, scientists have discovered that the yeast species used in the production of beer, bread and wine works particularly well in cacao fermentation.
For decades, researchers have worked to improve cacao fermentation by controlling the microbes involved.
“Chemical analyses as well as tasting the chocolate showed that the chocolate produced with our best yeasts is much better and more consistent than the chocolate produced through natural fermentation,” said Kevin Verstrepen, from the University of Leuven, and the Flanders Institute for Biotechnology (VIB), Belgium.
“Moreover, different yeasts yielded different chocolate flavours, indicating that it would be possible to create a whole range of speciality chocolates to match everyone’s favourite flavour,” said Verstrepen.
After the harvest, cacao beans are collected and placed in large wooden boxes, or even piled on the soil at the farms where they are grown, said Verstrepen.
At this point, the beans are surrounded by an unappetising white, gooey, pulp composed of sugars, proteins, water, pectin, and small amounts of lignin and hemicellulose.
Microbes that are present in the farm environment then go to work consuming the pulp through fermentation.
Differences among the microbes at different farms result in differences in flavour and quality of the resulting chocolate, said Verstrepen.
“Some microbes produce bad aromas that enter into the beans, giving rise to chocolate with a foul taste, while others do not fully consume the pulp, making the resulting beans difficult to process,” he said.
“We were looking to find or develop the best microbes that result in the best chocolate,” said Verstrepen.
These, he said, could be added immediately at the onset of fermentation, allowing them to outcompete less desirable microbes, enabling consistent production of high quality chocolate.
However, finding strains that could outcompete the undesirables and produce high quality chocolate proved highly challenging.
The investigators characterised more than 1,000 strains of Saccharomyces cerevisiae, mostly from the alcoholic beverage industry, but including some from cacao farms.
Some of the best performers came from the latter, and others came from the beer, wine, bioethanol and sake industries, said Verstrepen.
A key to success was the ability to tolerate the high temperatures encountered during cocoa fermentation – 45 degrees to 50 degrees centigrade.
The investigators then crossed some of the best strains, to produce hybrids which they found performed even better.