Predicting the dried moisture content in Fijian Theobroma cacao beans using a mechanistic model

Fiji exports dried Theobroma cacao beans based on global demand for high-quality Fijian cocoa beans. Standard processing protocols for cocoa beans are fermentation and sun drying for 14 days. The ideal moisture content for quality dried cocoa beans is between 10% and 7% on a wet weight basis. The extended drying time and intermittent drying conditions cause quality losses, particularly from mould growth. Drying can be controlled by using solar dryers integrated with a desiccant wheel for the dehumidification of air. The drying process can be numerically expressed using a drying model to predict the process conditions and drying time for cocoa beans. This study was the first to develop a mechanistic model using PDE to predict the drying kinetics for Fijian cocoa beans over a 36-hour dehydration period (i.e. two drying days and an intervening night). Drying consisted of preconditioning (6 h), followed by overnight tempering, and drying under dehumidification at 45 and 55 degrees C to a final moisture content of <10% (w.b). Drying at 55 degrees C under 15% relative humidity projected a final bean moisture content of <10% (w.b). The model is useful for predicting the quality of dried Fijian cocoa beans under differing drying conditions.