The unique flavor profiles of premium chocolate—which can include hints of citrus, wafts of wine and subtle notes of spice—have often been attributed to the cocoa bean’s origin. Farmers in tropical equatorial regions of the “cacao belt” have harnessed centuries-old harvesting techniques to coax cocoa beans that deliver the best taste—with the surprising help of tiny natural fermenters: microbes.
Now researchers have found that the fermentation fundamental to chocolate production can be reproduced with lab-controlled microbial communities to successfully re-create complex flavors of the beloved morsels.
“We have been able to change the flavors to kind of resemble different regions just by changing the microbes,” says David Gopaulchan, an international research fellow at the University of Nottingham in England and lead author of the new study describing the results in Nature Microbiology. “It’s like hacking an ancient process because we’ve been fermenting cocoa beans since we’ve had chocolate. That’s hundreds of years ago.”
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What Goes into Chocolate’s Taste?
Farmers grow cacao trees and harvest the pods, which are opened to collect the seeds and white, creamy pulp. This is left out to “cure” for several days in wooden boxes, baskets, Styrofoam coolers or large piles atop leaves on the ground—creating the perfect environment for microorganisms to ferment the beans.
“If you skip that that process, your beans don’t taste much like anything; it tastes more like plants. So the fermentation is super important in the development of flavor precursors,” Gopaulchan says. Other fermented foods such as wine, cheese and beer are often intentionally inoculated by the manufacturer, usually with the same strains of microorganisms. For chocolate fermentation, “it’s totally spontaneous and uncontrolled. It’s whatever microbes that exist at the farm,” he says.
This contributes to the enormous variety in fine chocolate flavors—and millions of farmers across the cacao belt each ferment beans with varying microbial communities, he says. The majority of cocoa beans produced globally go into bulk chocolate—that usually has a basic, bittersweet chocolate taste. But a smaller percentage go into fine flavor chocolate, which has a baseline chocolate flavor laced with a complex range of other notes.
For example, “my home country, Trinidad, is known for chocolates that taste like wine, but other regions like Venezuela are known for having very nutty flavor profiles in their beans,” Gopaulchan says.
Several other factors throughout the growing, harvesting and manufacturing process may influence the taste—including the soil, climate and bean genetics. “Plant genetics definitely play a huge role, but you can make bad chocolate out of good genetics with a bad fermentation,” says Caitlin Clark, senior food scientist at Colorado State University’s Spur Food Innovation Center, who was not involved in the new research.
Gopaulchan had previously investigated the role of diversity in cacao genes at the International Cocoa Genebank at the University of the West Indies, St. Augustine’s Cocoa Research Center. Along with farming locations, “it’s been the long-held belief that the flavor of chocolate largely depends on the genetics of the plant,” he says. “But what we show is that these microbes and this fermentation process have a huge impact. I would even argue it’s probably the largest impact on the final flavor profile.”
Controlling Fermentation, Controlling Flavor
In the new study, Gopaulchan and his colleagues collaborated with three cocoa farms in distinct environments in Colombia: the mountainous area of Santander, the dry valley of Huila and the Pacific zone of Antioquia. Using beans naturally fermented on-site, the team used DNA sequencing and metabolic modeling to identify the network of interactions between various bacteria and yeasts that drove fermentation.
Of the many microbes that were genetically identified, the team identified a core group that could reproduce the metabolic signatures—such as sensory volatile organic compounds—of fine chocolate flavor. The researchers isolated and tested these strains on unfermented beans in sterile wooden boxes under controlled conditions. Their analysis revealed that, chemically, the lab-fermented beans matched the flavor profiles of premium cocoa. But how did the beans taste?
The researchers had a trained sensory panel at the Cocoa Research Center taste cocoa “liquors”—semisolid pastes of ground roasted beans—from the three farms and the lab without knowing which was which. They scored the lab liquors—along with those from the Santander and Huila farms—as having attributes similar to the fine flavors of reference beans from Madagascar, while the Antioquia liquor was more similar to bulk cocoa.
“We found a lot of fruity, a bit spicy, floral-type flavors coming up with this community of microbes,” Gopaulchan says.
The findings support what farmers and the chocolate-making industry have seen in practice, Clark says. “Cacao fermentation is notoriously hard to study because it is so variable and you can’t really replicate it in a lab, so I thought they did a good job of knowing which factors to isolate and highlight,” she says.
Gopaulchan hopes that the proof-of-concept design could eventually lead to microbial “starters” to give farmers more control over the fermentation process and resulting flavors. Farmers, particularly small-scale ones, might be able to preserve the quality of their cocoa beans, Gopaulchan says, especially when fermentations fail from an unexpected rainy season or undesirable microbes.
Clark, however, sees such a platform mostly giving a leg up to large mainstream chocolate providers that try to closely control for consistency, batch after batch. “Variation in chocolate flavor is a real negative if you’re trying to make every Hershey’s chocolate bar across the world taste exactly the same every time,” Clark says. “Research like this benefits people trying to make chocolate taste the same a lot more than it benefits people trying to make chocolate taste interesting and different.”
Some companies have expressed interest in using this type of technology to create chocolate flavor without any cocoa beans at all, Gopaulchan says. But that could be “disruptive for the industry,” he adds.
Ultimately, he hopes that the research could aid fine flavor chocolate makers, too—maybe even by helping them design entirely new flavors. “We’ve identified microbes that make the cocoa beans taste more like cheese or wine. Others, you can get a strong meat flavor,” Gopaulchan says. “It’s wild that you could get a range of totally different flavors by just changing the microbe combinations. Now, we don’t want to eat cheesy chocolates, but I think, for other types of foods, there are possibilities.”