Drying behaviour of fermented Fijian Theobroma cacao using dehumidified air

Abstract

Fermentation and drying are two important postharvest processing stages for Theobroma cacao beans. In the Fiji Islands, tropical weather conditions favour fermentation but the high relative humidity impedes drying. Slow or intermittent drying leads to product loss from mould growth and spoilage, which is costly for the cocoa industry. Conversely, direct solar drying can lead to unacceptably high temperatures (over 60°C) and quality loss. Relative humidity can be controlled by applying low cost desiccant technology such as silica gel to dehumidify process air. The effect of dehumidified air on drying fermented T. cacao beans was evaluated at different drying temperatures of 56°C and 46°C. A rapid drying rate was achieved for fermented T. cacao beans dried at 56°C under 10% relative humidity. Drying was slower at 46°C under 18% relative humidity. Cocoa beans equilibrated to a moisture content <7% in 12 h and 34 h drying time respectively. Quality analyses are now under way to establish which of these drying profiles is preferable as a target for desiccant-assisted indirect solar drying.