b.) Drying

The drying process must be carried out carefully to ensure the beans are adequately prepared for storage and transport without becoming contaminated by moulds, Salmonella bacteria, PAH and other contaminants. Drying should be started immediately after the fermentation period to stop the beans from over-fermenting with consequent loss of cocoa flavour.

Although drying under direct, natural sunlight is preferable, it may be necessary to use artificial drying to complement or replace sun-drying depending on climatic conditions. Amoa-Awua has reviewed the different drying techniques, including solar and artificial dryers (Amoah-Awua, 2014). 

Drying by whatever means must be thorough, with the moisture content being reduced below 8% over an appropriate time period. This period will vary according to local conditions and/or whether artificial drying is used, but for sun-drying it should ideally be 6-10 days. 

Prolonged drying periods and re-wetting should be avoided since moisture contents over 8% can lead to secondary mould development, and thus mouldy/ musty off-flavours and the possibility of OTA production, inside the beans during subsequent storage and transport.

Care should be taken to control the rate at which drying occurs when using artificial dryers since when beans are dried quickly at elevated temperatures the rate of water loss from the shells is faster than the rate of migration of acids from the beans to the shells. 

Consequently, water is evaporated and lost in preference to the acids which are concentrated in the cotyledons or nibs where they not only give rise to an excessively acidic taste but also, they inhibit the cocoa flavour forming reactions during subsequent drying and roasting. 

Moreover, excessive drying will result in cocoa beans that are brittle and break easily, causing a high proportion of waste and fostering lipolysis and FFA development. In order to dry the beans effectively, with minimum exposure to contaminants, the following recommendations are made:

Drying surfaces/equipment should be located away from sources of contaminants and drying platforms should be elevated (ie the cocoa beans should not be spread out in direct contact with bare ground, tarmac or concrete floors) and protected from rodents, birds and livestock which can be a source of biological contamination.

Platforms for sun-drying should be sited so that they receive maximum sun exposure and air circulation during most times of the day, to speed up the drying process.

The layer of drying cocoa beans should not exceed 6cm thick, (40 kg of wet cocoa beans per square meter of drying area) to avoid slow or inadequate drying and the beans should be turned several times each day (about every two hours during daylight period with a resting or tempering period at night) to ensure uniformly dried beans. This also provides an opportunity for defective beans to be removed.

The beans should be protected from rain or dew, by heaping and covering the beans at night and when rain threatens, and re- spreading once the drying surface has dried. There should be no mixing of cocoa beans at different drying stages and specific identification methods should be used in order to distinguish and identify each drying stage.

Where artificial drying is necessary, it is essential that wood fires and other forms of direct fuel burners are not used since these will result in smoky off-flavours and PAH contamination. 

Fuel-burning dryers must incorporate heat exchangers and be designed, operated and maintained so that combustion gas and smoke does not come into contact with the beans during drying or while the dried beans are being stored to prevent off- flavours and contamination by PAH and other mineral oil hydrocarbons.

Smoke contamination and related PAH contamination are very obvious when beans are dried by wood fuelled kiln dryers. When direct fuel burners are used it may be less obvious that contamination has occurred, since there may not be the distinctive smoky aroma, but the beans may well be contaminated with PAH.