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The production of chocolate, one of the world’s most beloved sweets, is a multi-step process starting with freshly harvested cocoa beans. People have been experimenting with making chocolate for millennia, and even today new methods are still being introduced. Now the researchers who report in ACS’ Journal of Agricultural and Food Chemistry discovered that an alternative processing step called “wet incubation” results in a fruitier, flowerier dark chocolate than the conventional fermentation process.

Once the cocoa beans are harvested, they are traditionally covered with banana leaves and left to ferment for a few days. During this time, microbes in the environment break down the pulp surrounding the beans, heating them up and acidifying them. This causes biochemical changes in the beans that reduce bitterness and astringency, while developing the pleasant flavors and aromas associated with chocolate. Recently, scientists have developed an alternative, non-microbial approach called wet incubation, in which dried, unfermented cocoa nibs are rehydrated in an acidic solution, heated for 72 hours, and then dried again. The method, which is faster and easier to control than fermentation, produced similar flavors in the fermenting beans, with some differences. Irene Chetschik, Ansgar Schlüter and their colleagues wanted to find out how the taste and aroma of the end product – chocolate – compared when using wet incubation versus traditional fermentation.

The researchers made chocolate bars using incubated or wet-fermented dried cocoa beans, along with unfermented beans as a control. Sensory panelists said the moist incubated sample had higher intensities of fruity, flowery, malty, and caramelized aromas, while the fermented one had more roasted aromatic notes and the unfermented bean-based bar had an aroma mostly green. Panelists rated the wet incubated sample as the sweetest, while the unfermented chocolate was the most bitter and astringent. Identification of aromatic compounds by gas chromatography (GC)-olfactometry and their subsequent quantification by GC mass spectrometry revealed higher levels of malty compounds called Strecker aldehydes and lower amounts of roasted compounds called pyrazines in the moist incubated chocolate versus fermented one. The researchers concluded that wet incubation produces chocolate with a pleasant aroma and taste and could therefore serve as an alternative post-harvest treatment.

The authors acknowledge funding from the Zurich University of Applied Sciences (ZHAW).

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