Before it was not properly understood whether yeasts produced during fermentation had any impact on the quality of the cacao beans that go on to make chocolate.
But researchers from the University of New South Wales, led by Graham Fleet, claim that without yeasts at fermentation chocolate tastes acid and lacks its characteristic flavor. Their findings have been published in the International Journal of Food Microbiology.
The researchers said that future research could determine which yeasts produced the finest quality beans for chocolate, paving the way towards adding starter cultures to the fermentation process to promote particular strains of yeast known to be beneficial.
Naturally occurring yeasts
Fermentation usually takes place at plantations and methods varying considerably depending on the region.
Under the fermentation process in West Africa, where the majority of cocoa originates, wet cacao beans are heaped into a pile, covered by leaves and left to rest for five to six days.
During the process various species of yeast, lactic acid bacteria and acetic acid bacteria grow. The yeasts come from the surrounding environment such as the soil and trees.
“Although chocolate manufacturing is a multibillion dollar industry, estimated to have a global value of approximately US$ 95 billion, bean fermentation is still an uncontrolled traditional process conducted by a consortium of indigenous species of yeasts, lactic acid bacteria and acetic acid bacteria,” said the study.
The researchers determined that the microbial groups were essential to the fermentation process and the final quality of chocolate by seeing what would happen when they added Natamycin, a food additive that inhibits yeast growth.
They compared the Natamycin fermented beans to normal (control) fermentations and found that the beans without yeast were inferior.
“Quality tests revealed that beans fermented without yeasts were purplish-violet in color and not fully brown, and chocolate prepared from these beans tasted more acid and lacked characteristic chocolate flavor.”
“Beans fermented with yeast growth were fully brown in color and gave chocolate with typical characters which were clearly preferred by sensory panels. Our findings demonstrate that yeast growth and activity were essential for cocoa bean fermentation and the development of chocolate characteristics.”
International Journal of Food Microbiology Vol. 174, 2014, 72–87
‘Yeasts are essential for cocoa bean fermentation’
Authors: Van Thi Thuy Ho, Jian Zhao and Graham Fleet