Find out yeast's 'chocolaty' secret....

For years humans have used yeast to make bread, beer, and wine and the wild strains of yeast are also found in the natural fermentations that are essential for chocolate and coffee production.

But, as new genetic evidence reported in a recent study, the yeasts associated with coffee and cacao beans have had a rather unique history.

In comparison to the yeasts found in vineyards around the world, the new work shows that those associated with coffee and cacao beans show much greater diversity. The findings suggest that those differences may play an important role in the characteristics of chocolate and coffee from different parts of the world.

Researcher Aimee Dudley said that their study suggests a complex interplay between human activity and microbes involved in the production of coffee and chocolate.

Dudley added that humans have transported and cultivated the plants, but at least for one important species, their associated microbes have arisen from transport and mingling in events that are independent of the transport of the plants themselves.

Coffee and cacao trees originally grew in Ethiopia and the Amazon rainforest. They are now widely cultivated across the bean belt that surrounds the equator. After they are picked, both cacao and coffee beans are fermented for a period of days to break down the surrounding pulp. This microbe-driven process also has an important influence on the character and flavor of the beans.

The findings show that the yeast strains associated with coffee and cacao have multiple, independent origins. In other words, not all coffee strains are related, nor are all cacao strains. What's more, the yeast strains associated with coffee or cacao in specific places appear to be hybrids that resulted from the mixing of strains from different parts of the world. In fact, one of those strains is closely related to the yeast used to make wine.

The researchers said that the findings could lead to improvements in chocolate and coffee. Studies of wine production have shown that the yeasts associated with fermentation significantly influence the properties of the wine, including its flavor and aroma.

The research is published in the journal Current Biology.