Fermenting Cocoa


Chocolate has been around for millennia in various forms, and people have experimented with different methods of processing it for nearly as long. Even today, researchers at the American Chemical Society have discovered a new Cocoa post-harvest treatment that could serve as an alternative to traditional fermentation. The new method, called ‘moist incubation’, reportedly produces fruitier and more floral flavours in dark chocolate.

Traditional Fermentation Method

Historically, Cocoa beans are fermented after harvest, in a process that involved wrapping them in banana leaves and leaving them out for a number of days to allow natural microbes to break down the surrounding pulp. The process heats and acidifies the beans, which in turn reduces their bitterness, producing the more appealing flavours we associate with chocolate.

Moist Incubation

The new moist incubation method discovered by scientists Karin Chatelain, Sascha Rohn and their colleagues forgoes the use of microorganisms, in favour of a more controlled approach. Their method involves taking dried, unfermented Cocoa nibs and rehydrating them in an acidic solution. The rehydrated Cocoa nibs are then heated for 72 hours before being re-dried, a process that is both faster and easier to control than traditional fermentation. The resultant Cocoa beans are similar in aroma to those that undergo fermentation, but with a few key differences. 

The Comparison

The researchers compared chocolate produced from moist incubated Cocoa beans with chocolate made from fermented beans in order to see how the new method affected the final product. Unfermented beans were also used in the experiment as a control. The sensory panellists recruited for the experiment reported that the samples produced using moist incubation had more intense fruity, flowery, malty and caramel-like aroma notes. In comparison, the chocolate made with fermented beans was said to have a greater ‘roasty’ aroma, while the unfermented bean chocolate was said to be bitter and astringent with a ‘green’ aroma. The moist incubated chocolate samples were also described to have the sweetest flavour of the selection.

Taking a closer look at the aroma compounds found in the chocolate, using gas-chromatography-olfactometry (GC-O), it was discovered that the moist incubated chocolate contained higher levels of malty Strecker aldehyde compounds than its fermented counterpart. Strecker aldehyde compounds can also be found in beer, where they are responsible for the malty characteristics.

In addition, they also identified lower levels of pyrazines, which produce a roasty aroma, in line with the feedback from the sensory panel. 

Moist incubation revealed that the chocolate had a pleasant floral and fruity aroma, distinct from the more roasty characteristics of traditional chocolate. The resulting aroma and sweetness of chocolate produced this way could appeal to those who currently avoid dark chocolate because of the associated bitterness. This incubation method could, therefore, serve as a viable alternative for post-harvest treatment.

Photo by: Department of Foreign Affairs and Trade | Flickr


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