Fermentation and Chocolate Flavor: A Rarely Discussed Relationship

Fermentation is a crucial step in the transformation of cacao beans to what we know as chocolate. Without fermentation cacao beans yield little or no chocolate flavor. The principal effect of fermentation is to eliminate or, at least, drastically reduce astringency and to develop the full cacao flavor.

Astringency is the drying sensation in the mouth. This is the effect you get when chewing on grape skins or eating a bit of the interior skin of an underripe banana. Astringency is reduced by adequate fermentation. Astringency should not be confused with bitterness which is associated more with the caffeine-like chemical in chocolate called "theobromine".

Fermentation must be carried out on or near the farm. It involves removing the cacao seeds and the pulp that surrounds them from the protective pod shortly after the harvest. The pulp and the forty or so seeds are then placed on the ground or in a wooden bin and covered with banana leaves. Yeast in the environment settles on the pulp and ferments natural sugars in it to alcohol, at which point acetic acid (vinegar)-producing bacteria, as well as bacteria that produce lactic acid from residual sugar, take over. As acids are produced during this procedure the pH of the seeds decreases and the temperature rises as high as 140 F. The combined effects of the acidity and alcohol production in the fermentation process acts to kill the cacao seed. When the seed dies, internal structures break down and allow previously segregated compounds to combine with one another. This results in a host of new compounds (and a marked increase in flavor complexity) and a decrease in the concentration of the small polyphenol molecules most responsible for astringency.

It takes from between four and seven days to complete fermentation. But it is not a matter of simply leaving the beans alone for that period of time. In order to properly ferment, the farmer must either have knowledge based on experience or have the ability to measure a variety of parameters that govern timing of tasks such as turning the mass of cacao beans. Unfortunately, this process is rarely accomplished these days.

Some countries,(Ghana for example) produce relatively well-fermented cacao on a consistent basis. Other countries lack the tradition of thorough fermentation that is passed from farmer to farmer as in Ghana. Most often, one finds cacao that is described as fermented but that is either inconsistent on a bag-by-bag basis or is unfermented. Pod or non-uniform fermentation affects flavor.

Why is well-fermented cacao so hard to source? The reasons are unclear. Economics is certainly one of them. It appears that many manufacturers and exporters do not have an interest in helping growers understand the benefits, both to the cacao and financially, of delivering well-fermented beans. Poor fermentation is often masked by either adding a large amount of sugar or by alkalization, both of which conceal astringency and the absence of real chocolate flavor.