How does fermentation change the colour and flavour of cocoa beans?

During the fermentation process, which lasts between one and seven days depending on the grade of the cocoa, significant chemical and physical changes occur within the beans. As the pulp’s juices drain away and the germ inside the seed is killed by the heat generated during the process, the interior of the bean develops a distinct reddish-brown colour.12

Simultaneously, the fermentation process initiates the development of the bean's flavour profile, resulting in a heavy, sharp fragrance. While fermentation is the starting point for these characteristics, further processing steps—such as roasting—are later used to refine the flavour, reduce acidity and astringency, and further deepen the colour of the beans.12