Developing a radio frequency-hot air spouting treatment for efficient dehydration of carrot cubes: Evaluation of the heating and moisture distribution uniformity

Quality losses by local overheating and thermal runaway are a tough challenge for radio frequency (RF) drying of high-moisture foods. A self-designed spouted bed device proven to improve the RF heating uniformity of granular samples with high moisture might become a potential solution to overcome the above quality issue. In this study, the spouted bed device was applied on carrot cubes selected as the model sample to evaluate effects of the electrode gap, inlet air temperature, and inlet air speed on the characteristics of RF-hot air spouting drying (RFHASD), with comparison to hot air-assisted RF drying (HARFD) and hot air drying (HAD). Results showed that the drying rate of RFHASD increased with the decreasing electrode gap or the increasing inlet air temperature, but kept little change under different inlet air speeds. In addition, RFHASD needed less time and energy consumption to finish the drying process than HARFD and HAD, and provided more uniform temperature and moisture distributions in products, leading to the best rehydration ratio, color, hardness, and chewiness. These findings demonstrated the unique advantages of RFHASD in drying high-moisture foods and may provide the theoretical basis for further industrial applications.