直触式超声强化热风干燥梨片的干燥特性

Drying characteristics of direct-contact ultrasound enhanced hot-air drying of pear slices

为探讨直触式超声强化热风干燥梨片的干燥特性,进行梨片超声强化热风干燥试验,研究超声功率及热风温度对梨片干燥过程及产品品质的影响规律。结果表明:提高热风温度及直触式超声功率能够明显缩短干燥时间,较低温度下的超声强化效果要好于较高温度下的。BP神经网络模型能较好地预测梨片超声强化热风干燥过程中的水分变化规律。超声产生的空化效应和机械效应可增大水分流动性及提高梨片的复水率,且有利于保留梨片营养成分,但干燥温度过高则不利于总酚、总黄酮、VC等热敏性营养成分的保留。梨片超声强化热风干燥过程的层次分析法优化结果表明,最优干燥参数为热风温度35℃、超声功率48 W,此时梨片总酚含量为408.88 mg/100g,总黄酮含量为157.94mg/100g,VC含量为42.36mg/100g,复水率为3.32。因此,将直触式超声强化技术用于梨片热风干燥中,能够显著缩短干燥时间、明显提高梨片干燥品质。

In order to explore the enhancing effect of contact ultrasound on hot air drying process,ultrasound enhanced hot air drying of pear slices was performed.The effects of different ultrasound powers and drying temperatures on drying characteristics and several quality indicators of pear slices were studied.The results showed that the improvement of hot air temperature and ultrasound power could significantly reduce drying time,and the stronger ultrasound enhanced effects could be achieved at lower temperatures.The BP neural network model was applied to predict the process of ultrasound enhanced hot air drying with high fitting precision.The cavitation and mechanical effects of ultrasound could increase moisture mobility and rehydration rate,and could improve the contents of the nutrients in pear slices.However,too high temperature was negative to the retention rate of total phenols,total flavonoids and ascorbic acid which were heat-sensitive nutrient components.The analytic hierarchy process was applied to determine the optimal parameters of ultrasound enhanced hot air drying of pear slices as hot air temperature of 35 ℃ and ultrasonic power of 48 W.The corresponding total phenol content,total flavonoid content,VCcontent and rehydration ratio were 408.88 mg/100 g,157.94 mg/100 g,42.36 mg/100 g and 3.32,respectively.Therefore,the reduction of drying time as well as the improvement of product quality could be achieved with the application of contact ultrasound on hot air drying of pear slices.