Chocolate production is a multi-step process that starts with freshly harvested cocoa beans. Researchers reporting in the American Chemical Society’s Journal of Agricultural and Food Chemistry have found that an alternative processing step called “moist incubation” results in a dark chocolate that tastes ‘fruitier’ and more ‘flowery’ than that produced by the conventional fermentation process.
What is moist incubation?
Traditionally, after cocoa beans are harvested they are covered in banana leaves and left for a few days to ferment. During this time, microbes in the environment degrade the pulp surrounding the beans, heating and acidifying them. This causes biochemical changes in the beans that reduce bitterness and astringency, while developing the pleasing flavours and aromas associated with chocolate.
Scientists have developed an alternative, non-microbial approach called moist incubation. This sees dried, unfermented cocoa nibs rehydrated in an acidic solution, heated for 72 hours and then re-dried.
The research claimed the method is faster and more easily controlled than fermentation. It was found that this approach produced similar aromas in beans as fermentation, with some differences. Irene Chetschik, Ansgar Schlüter and colleagues – who funded were by Zurich University of Applied Sciences (ZHAW) - wanted to find out how the taste and aroma of the final product — chocolate — compared when using moist incubation versus traditional fermentation.
Putting moist incubation to the taste test
The researchers made chocolate bars using moist incubated or fermented dried cocoa beans, as well as unfermented beans as a control.
Sensory panellists said the moist incubated sample had higher intensities of fruity, flowery, malty and caramel-like aromas, whereas the fermented one had higher roasty aroma notes, and the bar made from unfermented beans had a primarily green aroma.
The panellists rated the moist incubated sample as the sweetest-tasting, while the unfermented chocolate was the most bitter and astringent. Identification of aroma compounds by gas chromatography (GC)-olfactometry and their subsequent quantitation by GC-mass spectrometry revealed higher levels of malty compounds called Strecker aldehydes and lower amounts of roasty compounds called pyrazines in the moist incubated chocolate compared with the fermented one.
The study concluded that moist incubation produces a chocolate with a ‘pleasant aroma and taste’ and could, therefore, serve as an alternative postharvest treatment.
‘Comparison of the aroma composition and sensory properties of dark chocolates made with moist incubated and fermented cocoa beans’
Journal of Agricultural and Food Chemistry