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[摘要]
目的 以枸杞为研究对象,探索枸杞的真空脉动干燥过程中水分变化规律及动力学模型,为改善表面结壳,缩短干燥时间提供理论依据。方法 将真空脉动干燥技术应用于枸杞的干燥,研究不同干燥温度(50、55、60、65℃)、真空时间(5、10、20、30 min)和常压时间(2、4、8 min)对枸杞干燥动力学、水分有效扩散系数(Deff)和干燥活化能(Ea)的影响,利用Weibull分布函数对干燥过程进行模拟与分析。结果 干燥温度、常压时间和真空时间均对枸杞的干燥有显著影响,当干燥温度60℃,常压时间4 min,真空时间10 min时,干燥时间为284 min;Weibull分布函数能很好地描述枸杞的真空脉动干燥过程;尺度参数α与干燥时间有关,并随干燥温度的升高而降低;干燥温度、真空时间和常压时间对形状参数β的影响较小,β值和干燥方式相关;水分Deff在2.02×10-8~3.56×10-8 m2/s,干燥Ea为36.27 kJ/mol。结论 Weibull分布函数可预测枸杞药材真空脉动干燥过程中的水分脱除规律,对于枸杞干燥过程的预测、调控和工艺优化具有重要意义。
[Key word]
[Abstract]
Objective To mitigate Lycii Fructus surface crust and save drying time during drying process, vacuum pulsed drying technology was applied to dry Lycii Fructus so as to investigate moisture diffusion regulation and build the drying model. Methods The effect of different drying temperature (50, 55, 60, and 65℃), vacuum pressure holding time (5, 10, 20, and 30 min), and atmosphere pressure holding time (2, 4, and 8 min) on drying characteristics, moisture diffusion coefficients and drying activation energy was explored in vacuum pulsed drying process. Weibull model distribution was used to simulate and analyze Lycii Fructus drying curves. Results All the drying temperature, atmosphere pressure holding time, and vacuum pressure time holding time had significant influence on drying time. When drying temperature, atmosphere pressure holding time, and vacuum pressure time holding time was 60℃, 4 min, and 10 min, respectively, the minimum drying time was achieved to be 284 min. Weibull distribution model can be well described the vacuum pulsed drying process of Lycii Fructus. The scale parameter was related to drying time and decreased as drying temperature increased. The drying temperature, atmosphere pressure holding time, and vacuum pressure time holding time had little influence on the shape parameter. The shape parameter was associated with drying method. The moisture diffusion coefficient and activation energy were calculated to be 2.02×10-8-3.56×10-8 m2/s and 36.27 kJ/mol, respectively. Conclusion Weibull distribution model can well describe the moisture diffusion regulation of vacuum pulsed drying process of Lycii Fructus. The drying result had a great significance for predicting, controlling and optimizing drying process. On the other hand, the research could provide technical basis for industrial drying of Lycii Fructus by vacuum pulsed drying technology.
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[基金项目]
现代农业产业技术体系建设专项资金资助(CARS-21);石家庄市科学技术研究开发项目(171170982A)