The secret ingredient that makes chocolate taste so good: fermenting microbes!
In chips in a cookie, melted in a hot, sweet drink or molded into the shape of an Easter bunny, chocolate is one of the most consumed foods in the world.
However, few people know, even the greatest amateurs, that chocolate has something in common with kimchi and kombucha: its flavors are the result of fermentation. That familiar, beloved taste comes from tiny microorganisms that help transform the raw chocolate ingredients into this rich, complex end product.
In labs from Peru to Belgium to the Ivory Coast, self-proclaimed chocolatier scientists like me strive to understand how fermentation changes the flavor of chocolate.
Sometimes , we create artificial fermentation processes in the laboratory. Other times we take samples of cocoa beans from real “natural” fermentations. Often we turn our experimental batches into chocolate and ask a few happy volunteers to taste it and tell us what flavors they detect.
After decades of tests like this, researchers have solved many mysteries about cocoa fermentation, including the microorganisms involved and how this step influences the flavor and quality of chocolate.
From the pod to the bar
The food you know as chocolate begins its life as the seeds of football-shaped fruit pods that sprout directly from the trunk of the Theobroma cacao tree. It sounds like something Dr. Seuss, a children's author, would have devised. But already 3,900 years ago, the Olmecs of Central America understood that the transformation of these giant pods into an edible delicacy, involves several stages.
Inside the pods are the seeds and the pulp. Camille Delbos/Art In All of Us/Corbis via Getty Images
First, workers crack open the brightly colored fruit and extract the seeds and pulp. The seeds, now called “beans”, harden and drain for three to ten days before drying in the sun. The dried beans are roasted, then ground with sugar and sometimes powdered milk until the mixture is so smooth you can't make out the particles on your tongue. At this point, the chocolate is ready to be shaped into bars, shavings or confections.
It is during the drying phase that fermentation occurs naturally. The complex aroma of chocolate is due to hundreds of components, many of which are generated during fermentation, i.e. during the process of improving the qualities of a food by the controlled activity of microbes. It allows bitter, otherwise tasteless cocoa nibs to develop the rich flavors associated with chocolate.
The beans dry in the sun on a plantation in Madagascar, while the microbes do their job. Andia/Universal Images Group via Getty Images
Micro-organisms at work
Fermentation cocoa is a multi-step process. Any micro-organic compound produced along the way that changes the taste of the beans will also change the final taste of the chocolate.
The first stage of fermentation may be familiar to home brewers, as it involves yeasts, some of which are the same ones that ferment beer and wine. Much like the yeast in your favorite beer, the yeast in a cocoa fermentation produces alcohol by digesting the sugary pulp that coats the beans.
This process generates fruity-tasting molecules called esters and alcohols with a floral taste. These compounds soak into the beans and are then present in the final product.
As the pulp decomposes, oxygen enters the fermenting mass and the yeast population decreases, giving way to oxygen-loving bacteria. They are known as acetic acid bacteria because they convert the alcohol generated by yeast into acetic acid.
The acid enters the beans, causing biochemical changes. The germinating plant dies. Fats clump together. Some enzymes break down proteins into smaller peptides, which become very “chocolatey” during subsequent roasting. Other enzymes break down antioxidant polyphenol molecules, for which chocolate is considered a superfood. Therefore, contrary to their reputation, most chocolates contain very few polyphenols, if any at all.
All of the reactions triggered by acetic acid bacteria have a major impact on flavor. These acids promote the breakdown of highly astringent, deep purple polyphenol molecules into milder-tasting, brown-colored chemicals called quinones. This is where the cocoa beans change from a bitter taste to a rich, nutty taste. This transformation in taste is accompanied by a change in color, from purple-red to brown, and this is the reason why the chocolate you know is brown and not purple.
Finally, as the acid slowly evaporates and the sugars are depleted, other species – including filamentous fungi and spore-forming Bacillus bacteria – take over.
< p>As essential as microbes are in the chocolate making process, certain organisms can sometimes ruin a fermentation. Overgrowth of the spore-forming bacterium Bacillus is associated with compounds that impart a rancid and cheesy taste.
Terroir and its microbes
Cocoa is wildly fermented: farmers rely on natural microbes in the environment to create unique, local flavors. This practice that is said to be “terroir” reflects the specific characteristics of a place. In the same way that grapes take on the regional terroir, these wild microbes, combined with each farmer's particular process, give the fermented beans a taste of the terroir.
High-end chocolate makers are picky about the treatment of their beans. twohumans/E+ via Getty Images
Market demand for these fine, high quality beans is on the rise. Small-scale gourmet chocolate makers hand-select the beans based on their distinctive terroir, to produce chocolate with an impressive range of flavor nuances.
If you haven't experienced chocolate that in the form of a bar grabbed at the grocery store checkout, you have no idea the range and complexity that really high quality chocolate can exhibit.
A chocolate bar from the Madagascan estate of Akesson may recall raspberries and apricots, while Peruvian bars from Canadian chocolatier Qantu, wild-fermented, look like they've been dipped in Sauvignon Blanc. Yet in both cases, the bars contain nothing but cocoa beans and sugar.
This is the power of fermentation: change, convert, transform. It takes the ordinary and makes it extraordinary, thanks to the magic of microbes.
Caitlin Clark, Ph.D. Candidate in Food Science, Colorado State University
This article is republished from The Conversation under a Creative Commons license. Read the original article.