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Using methods such as dynamics and thermodynamics, the drying laws, dynamic models, moisture migration, thermodynamic parameters, etc. of citrus Gonggan slices during hot air drying at different temperatures were studied. The effects of ultrasound-microwave synergistic pretreatment on the drying efficiency of citrus Gonggan slices during hot air drying were also analyzed. The results showed that the drying process followed the Two term exponential model and the drying rate was co-related with the drying temperature. The drying rate was the fastest when the drying temperature was 80 °C. The ultrasound-microwave synergistic pretreatment effectively reduced the drying time by 0. 5 hours to 1. 5 hours. The activation energy (Ea) of moisture diffusion was significantly lowered by 1. 620 kJ/ mol. At a given hot air drying temperature, the ΔH≠, ΔS≠, and ΔG≠ of the ultrasound-microwave synergistic pretreatment group were all lower than the control group. The ultrasoundmicrowave synergistic pretreatment could increase the effective coefficient of water diffusion of citrus Gonggan slices (4.333 x 10-7 to 8. 967 x 10-7), resulting in more pores on their surfaces. Therefore, the ultrasound-microwave synergistic pretreatment could effectively improve the hot air drying efficiency of citrus Gonggan slices. [ABSTRACT FROM AUTHOR]

Lingnan characteristic fruits are prone to spoilage after harvesting, drying processing technology can be used to produce dried products that can effectively extend shelf life, reduce transportation costs, and enhance product value. A review of current drying technologies for Lingnan characteristic fruits (hot air drying, heat pump drying, microwave drying, spray drying, freeze drying and combined drying) was conducted to summarize their advantages and disadvantages as well as their effects on the quality of dried products. Drying temperature is a key factor affecting the quality of dried fruit products. Hot air drying is convenient to operate, but high temperature will reduce the quality of its products. Heat pump drying has less sensory loss of fruits, and is suitable for drying heat- sensitive fruits. Microwave drying has high drying efficiency, but the surface of dried fruit products will be burnt with excessive drying power. Spray drying has high efficiency and large processing capacity with good quality produced fruit powder. Freeze drying can maximize the flavor and nutritional content of fruits but consumes more energy, and combined drying can improve the efficiency and reduce energy consumption while improving the quality of fruit dried products by combining the advantages of single drying technology, however, the optimal process parameters need to be determined through a large number of experiments. In the future, we should combine advanced drying technology and equipments and utilize jointly the advantages of single drying technology to adopt appropriate drying processing technology and optimize the combined drying process for different characteristics of fruits, which has contributed to the improvement of drying efficiency and stability of dried product quality. This study aimed to provide references for the innovation-driven development of Lingnan characteristic fruit drying technology. [ABSTRACT FROM AUTHOR]