Scientific research

The objective of this study is to assess the quality of cocoa beans produced by smallholders from different regions in Malaysia, such as Sabah, Sarawak, Perak, and Pahang. Most of the samples were obtained from beans fermented in plastic sacks, with a fermentation duration of 5 days and dried using natural technique in 4-5 days. Results showed no significant difference (p>0.05) among the bean samples for moisture content, pH, degree of fermentation (cut test score and fermentation index), and sensory evaluation (cocoa, bitterness, astringency, and sourness flavour attributes) based on the different locations. Cut tests showed that all the samples were well-fermented with percent brown beans of more than 60% which agreed well with the fermentation index. The quantity of slaty and purple beans was higher in the Sarawak and Pahang samples as compared to the Perak and Sabah samples. The presence of these beans in high amounts is not desired as unfermented and underfermented beans tend to introduce excessive bitterness and astringency in the finished products.
The pH values were mostly at the less acidic level (pH > 5.50) except for the Pahang samples which were at the medium level (pH 5.20-5.49). The pH values recorded were much less acidic than those reported by Jinap et al. (1995) between 4.64 and 4.85 for Malaysian cocoa beans. Highly acidic beans are associated with pH of less than 5.2.
Highly acidic beans are associated with low chocolate flavour, possibly due to over degradation of storage proteins.

Selected references:

Duncan et al, 1989
Improvement of Malaysian cocoa bean flavour by modification of harvesting, fermentation and drying method - found that dissipation of acetic acid is more efficient in natural drying as compared to the faster artificial drying where entrapment of acids causes high acidic flavour in cocoa beans.

Jinap, 1994
Organic acids in cocoa beans - A review - found that the best flavoured West African beans usually have pH values around 5.5.
Jinap, 1995 - found that naturally dried cocoa beans have been reported to have better flavour quality as compared to artificially dried beans due to the gentle drying process. Also, that chocolate made from medium pH beans received a higher response in strong chocolate flavour than those made from low or high pH beans.

Shahrir and Mamot, 1987
Determination of fermentation Index (FI) and its application to cocoa quality and grading - found that the colour of unfermented beans is generally slaty, while underfermented beans are purple, and fully fermented beans are brown in colour.