Diverse yeasts make their home on coffee and cacao beans

When your barista says today’s cuppa joe has rich, spicy notes found only in Colombia’s soil or ‘terroir,’ he or she might not be completely full of … beans.  

Before going global, the coffee bean plant originated in Ethiopia, while cacao was first cultivated in the Amazon. Both coffee and cacao beans undergo fermentation prior to roasting. Wild yeast and other microbes that live on the bean digest the pulp that coats the beans, altering flavor and color as well. Researchers wondered, are these yeasts a product of the plants’ current geography or their original roots? 

So, they bought unroasted coffee and cacao beans from 27 countries, isolated bean yeasts and analyzed the yeasts’ genes. While coffee and cacao yeasts are even more diverse than wine yeasts, strains that came from the same continents and countries had more in common genetically with their immediate neighbors. Still, some cacao strains from South America share genes with European vineyard yeast and North American oak tree yeast. Such hybrids are probably the result of human trade and travel, the team reports March 24 in Current Biology.

Determining the flavor fallout of all this yeast diversity requires further study, but wine yeasts from different locales are linked to specific chemical profiles.