Publication in PPIA Bulletin
Cocoa Bean: Trade Standards, Postharvest Processing, Re-Emerging Spoilage Microorganism, and Quality Controls
December edition preview
A complex process is carried out before the bean traded and converted into consumable goods. Harvesting, fermentation, drying, storage and distribution are the common unit operations of cocoa bean. Inappropriate measurement of time, temperature and other environmental conditions can increase probability for mycotoxigenic fungi to grow.
Cocoa bean is actually seed of Theobroma cacao L trees and is covered in mucilaginous pulp inside cocoa pods. During harvesting, seed and the associated pulp are removed from the pods, mainly by hand or simple tools, followed by spreading into heap, boxes, or trays for fermentation.
The bean is allowed to ferment for various durations, depending on the farmer practises, but it mainly occurs for 6-12 days. The fermentation is a traditional (natural) process that is conducted by growth of indigenous microflora, which leads to the occurrence of toxigenic fungi.
The role of filamentous fungi during fermentation course was reported. At the very early stage of fermentation, from 0-48 hours, some Aspergillus and Penicillium species are found at 102-103 CFU.g-1 and probably contributing to pectin degradation of the pulp. The growth of fungi is not detected (<100) after 48 hours, because they die off due to increasing ethanol concentration. However, since there is no standardized practice for cocoa processing at the farm level, the role and diversity of microbiota in fermentation are widely reported.
Fully fermented beanis dried, either in a mechanical dryer or traditionally solar dried, to achieve 6-7% recommended moisture content. The drying stage is slow and time consuming (3-6 days), and subjected to climate conditions. In tropical countries, high humidity in combination with warm temperature is the main problem.
The dried bean is easily re-wetted due to high humidity at rainy season or during the night. The high moisture and nutritious properties of the bean provide ideal conditions for fungi to grow. An increase in humidity and moisture content can also occur during transportation of bean from tropical countries to cooler countries. Fungal spores may be able to germinate and can grow in the bean to cause product spoilage and rejection. In addition, they could also produce mycotoxins. The chemical structures of toxins are extremely stable to heat and acid treatment.
Regardless countries of origin, cocoa bean are susceptible to spoilage by filamentous fungi. Currently, there is an increasing concern that fungal contamination could also result in the production of mycotoxins, in particular aflatoxins and ochratoxin A, which have significant public health consequences since they could be carcinogenic. The occurrence of mycotoxins in cocoa bean is under reported, but recent studies found the presence of ochratoxin A. These data suggest the need to amend cocoa bean trading standards to include the presence of mycotoxins.
With current practises, there is no cost-effective solution to reduce the level of toxins in agricultural products once they have been produced. Therefore, good production practises are required to control bean properties and made them less favourable for mould growth.
In summary, there is significant potential for filamentous fungi to grow in cocoa bean and compromise their growth by causing spoilage and producing mycotoxins. Recent, it has suggested that mycotoxins presence will be increasing concern to the chocolate industry. More information is needed about the occurrence of filamentous fungi, especially mycotoxigenic species, in dried cocoa bean.