Ultrasonic assisted far infrared drying characteristics and energy consumption of ginger slices

Three drying methods, including far infrared drying, infrared convection drying, and ultrasonic pretreatment assisted far infrared drying, were adopted in the drying of ginger slices. The effects of main parameters (ultra-sonic pretreatment power and time, far infrared temperature and power, sample thickness, infrared convection temperature) on the drying kinetics, energy consumption, and color change were investigated and discussed in detail. The results showed that the drying process of ginger slices was controlled by falling rate period. For far infrared drying, the drying rate increased with the increase of infrared temperature and decrease of sample thickness, while the infrared power had no obvious effect on the drying process. The infrared convection drying showed the fastest drying rate and the smallest color change, however, the energy consumption was the highest. For ultrasonic pretreatment assisted far infrared drying, an appropriate ultrasonic pretreatment time and power would promote the far infrared drying process and the energy consumption was only slightly increased. How-ever, the color change was relatively large. The ultrasound technology showed its greatest potential to enhance the drying rate at the early stage of drying and increasing ultrasonic power was more effective than prolonging the pretreatment time in promoting far infrared drying.