中文摘要：

为探讨直触式超声对热风干燥过程的强化效果，以紫薯为干燥试材，利用超声热风干燥设备，研究不同干燥温度（40、50、60、70℃）及不同超声功率（0、30、60W）条件下，紫薯片的干燥特性和品质变化规律，并利用Weibull函数对干燥过程进行了动力学模拟。结果表明：随着干燥温度的升高和超声波功率的增加，干燥时间明显缩短，干燥速率显著提高；Weibull分布函数可实现较高的模型精度；尺度参数α范围在92.317～345.764min之间，且随着干燥温度升高和超声功率增大而减小，形状参数β在0.817～1.032之间，表明超声强化热风干燥紫薯的干燥过程由内部扩散阻力控制；水分扩散系数Dcal的范围为1.205×10－10～4.513×10－10m2/s，其值随干燥温度和超声功率的升高而增大；干燥活化能随着超声功率的增加而相应减少；在相同超声功率下，随着干燥温度升高，总酚和总黄酮含量基本呈现先升高后下降的趋势；在较低干燥温度条件下，增大超声功率有利于提高总酚和总黄酮含量，但在较高温度条件下，增大超声功率则不利于总酚和总黄酮成分的保持。将超声技术用于热风干燥过程的强化可有效提高干燥速率和干燥品质。

英文摘要：

In order to explore the enhancing effect of ultrasound on hot air drying process,the drying characteristics and quality changes of purple-fleshed sweet potato in an ultrasound-assisted hot air dryer were investigated at different drying temperatures(40,50,60and70℃)and ultrasound powers(0,30and60W).The Weibull distribution model was applied in the dynamic simulation of the drying process.The results showed that the increase in drying temperature and ultrasound power resulted in a significant reduction in drying time.The Weibull distribution model could fit the drying curves accurately under different drying conditions.Scale parameter(α)decreased in the range of92.317to345.764min with the increase in drying temperature and ultrasound power.Shape parameter(β)ranged from0.817to1.032,indicating that the hot air drying of purple-fleshed sweet potato was controlled by internal diffusion resistance.The effective moisture diffusivity coefficient(Dcal)values increased in the range of1.205×10-10to4.513×10-10m2/s with the increase in drying temperature and ultrasound power.The activation energy decreased as ultrasound power increased.At the same ultrasound power,the contents of total phenolics and total flavonoids increased at first and then decreased with the increase in drying temperature.Both classes of compounds increased with the increase in ultrasound power at lower drying temperature,whereas the reverse trend was observed at higher drying temperature.Therefore,ultrasound-assisted hot air drying is an effective method to accelerate drying rate and simultaneously achieve better quality.