Empirical Study of the Energy Demand and Drying Behaviour of Selected Tuber Crops

This study investigated the persistent challenge of post-harvest losses in selected tuber crops, namely white yam (Dioscorea rotundata), trifoliate yam (Dioscorea dumetorum), and cocoyam (Xanthosoma sagittifolium), which are staple crops of major nutritional and economic significance in Nigeria. This research empirically characterised the drying behaviour and energy demand of white yam, trifoliate yam, and cocoyam under microwave oven drying conditions. Specific objectives included evaluating the effects of key process parameters—temperature (40, 45, 50 °C), air velocity (2, 3, 4 m/s), and slice thickness (3, 4, 5 mm)—on drying kinetics, energy efficiency, product shrinkage, effective moisture diffusivity, and activation energy. The study assessed the performance of ten thin-layer drying models to determine the most appropriate for describing tuber drying behaviour under microwave conditions. Findings revealed that drying occurred predominantly within the falling rate period. Cocoyam exhibited the fastest drying rate and highest effective diffusivity, while trifoliate yam showed the slowest moisture removal. Increased temperature, elevated air velocity, and reduced slice thickness significantly enhanced drying efficiency. Optimal conditions were achieved at 45°C and 3 m/s. Among the tested models, the Midilli et al. model consistently provided the best fit, with R² values exceeding 0.988. The study concludes that microwave drying is highly effective for selected tubers, with performance critically dependent on process parameters, and that microwave oven drying is highly effective for selected tubers, with performance critically dependent on process parameters. The study, therefore recommends 50 °C, 4 m/s, and 3 mm slicing for industrial use, and proposes further research into nutritional retention and the validation of the Specific Thin-Layer Drying Model for Yam Tubers (STLDMYT).