Performance evaluation of MOF-coated desiccant-assisted intermittent heat pump drying for energy-efficient dehydration of apple slices

The pursuit of energy-efficient drying technologies that preserve product quality is crucial in food preservation. This study explores a novel method utilizing metal–organic frameworks (MOFs) coated on an auxiliary condenser to enhance the performance of heat pump drying systems for apple slices. The research is structured in two phases. The first evaluates drying behavior under continuous and intermittent modes, emphasizing drying curves and system efficiency. The second phase integrates an MOF-coated desiccant-coated heat exchanger (DCHE) into intermittent drying, employing a bypass air duct for improved dehumidification. An exponential model was adapted for intermittent operation. The model effectively predicted the moisture ratio (MR) with high accuracy, achieving R2 values of 0.9703 for 2.5 mm slices and 0.9621 for 5 mm slices. MOF-DCHE-assisted intermittent drying reduced drying time by 18.18 % (5 mm slices) and 6.67 % (2.5 mm slices), at intermittent ratios of 0.54 and 0.88, respectively. Additionally, it improved the specific moisture extraction rate (SMER) by 5.4 % for 5 mm slices and 3.7 % for 2.5 mm slices compared to non-assisted modes. Energy consumption was reduced by 25.5 % for 5 mm slices compared to continuous drying. Sensory analysis confirmed excellent retention of key attributes such as flexibility, aroma, flavor, and overall liking, highlighting enhanced product quality. Integrating MOF-DCHE into heat pump drying systems thus demonstrates a promising and sustainable method for improving drying efficiency, reducing energy consumption, and preserving the dried fruit quality.