1.5. Bitterness & Astringency

Some bitterness and astringency is part of the complex of overall flavour development but if either is present in excess it becomes objectionable.

Some bitterness and astringency are part of the complex of overall flavour development but if either is present in excess it becomes objectionable. Excessive bitterness and astringency cannot be removed by normal factory processing.

These flavours are associated with poor fermentation and/or certain varieties. Unfermented or slaty beans, as revealed in the cut test, can result in extremely bitter and astringent cocoa mass. 

The Ghana Cocoa Board, for example, sets a maximum limit of 3% slaty beans for Grade 1 cocoa to ensure it does not impart excessive astringency to chocolate. Fully purple beans also produce bitter and astringent flavours. 

While excessive amounts of slaty and purple beans should be avoided, chocolate manufacturers do not expect to receive beans which are all fully brown.

Even cocoa that has been correctly harvested, fermented and sun-dried may contain a proportion of partly brown/purple beans.

Studies have shown that planting materials differ markedly in astringency and in their concentrations of polyphenols which contribute directly to that flavour characteristic (for example Elwers et al., 2009). 

The concentrations of polyphenols are reduced markedly during post-harvest processing but not to the same limiting concentration for all planting materials, assuming that a standardised processing treatment has been used.