高压电场干燥枸杞机理和数学模型的研究

At present, the conventional drying processes of Chinese wolfberry include solar drying and hot air drying etc. These drying processes often cause adversely affects texture, color, and nutritional value of Chinese wolfberry. As the result, the product quality is often poor. High-voltage electric field drying is a relatively new, nonthermal drying technique, and it has been investigated by many researchers in vegetables, fruits, aquatic food, grains, and other heat-sensitive materials. But, it is not a profoundly studied the method of drying, especially in the drying mechanism and mathematical models. In this project, Chinese wolfberry would be dried in high-voltage electric field system in order to study the drying characteristic, product quality and technological parameter. The drying mechanism would be investigated based on the characteristic of the high voltage electric field and Chinese wolfberry. The mathematical models that described the drying processes and diffusion model of moisture in the material would be established. This would reveal the drying discipline of Chinese wolfberry in high-voltage electric field system. This work provides the theoretical foundation for drying process control and prediction of Chinese wolfberry in high voltage electric field system. It also provides the theoretical foundation for the extensive application of high-voltage electric field drying technology. We hope to contribute to the prosperity of the local economy and the increase of the farmers' income.

枸杞干制广泛采用晒干或烘干等传统技术，存在产品有效成分损失大和品质差等缺点。高压电场干燥技术是一种新型的干燥技术，具有非常多的优点。但针对高压电场干燥的研究都是在初步的实验阶段，干燥模型的研究也在初步阶段，干燥机理尚不清楚。本项目运用高压电场干燥技术对枸杞进行处理，对其干燥特性、产品品质、工艺参数进行较基础性研究。在前期研究的基础上，从电场特性和枸杞性质两方面入手对干燥机理进行更深入的研究，建立能够反映干燥过程的数学模型和干燥物料中的水分扩散模型，揭示枸杞的高压电场干燥规律。此项目为枸杞高压电场干燥的过程控制和预测提供理论依据；同时为高压电场干燥技术更广泛的应用提供理论基础；希望为繁荣当地经济和增加农民收入出一份力。

本项目针对高压电场干燥技术的缺点进行了研究。首先全面、系统地研究了高压电场中不同参数下枸杞的干燥特性和干制品的品质。其次理论上对高压电场特性进行了计算，在实验上进行了介质阻挡离子风干燥等实验，并测量了枸杞细胞损伤率和干燥过程中枸杞的有效水分扩散系数，借助扫描电镜，红外光谱等手段分析了微观结构，通过这些对高压电场中枸杞的干燥机理进行了系统研究。最后借鉴一些经验，半经验的数学模型模拟干燥过程，分析了高压电场中枸杞的干燥数据。同时作为拓展，研究了高压电场作用下胡萝卜的干燥特性和不同电场参数下冻豆腐的解冻特性。. 本项目的重要研究结果包括：（1）在不同电场参数下高压电场能够很大程度上提高枸杞的干燥速度，很好地保持枸杞内部的有效成分,对枸杞复水率影响较大，对收缩率的影响较小，进而提高干制品品质，且单位消耗能量较低。（2）理论上计算可知，高压电场干燥中离子风的作用较大，非均匀电场的作用小一些。实验上发现，离子风对枸杞的细胞损伤率和水分有效扩散系数影响较大，进而大幅度提高干燥速度，起到的作用大于非均匀电场。离子风和非均匀电场都可以提高有效成分的保持。借助红外光谱和扫描电镜等手段发现高压电场对微观结构有很大影响。（3）很多经验，半经验的数学模型都可以用来描述枸杞在高压电场下的干燥特征，只是不同条件下最佳模型稍有不同。（4）高压电场能够提高胡萝卜的干燥速度，提高胡萝卜的有效成分保持，Page模型比较适合模拟干燥曲线。在高压电场作用下豆腐的解冻速度大大地提高，且随着电压增大，豆腐的解冻时间减小。随着电压增大，总损失率减小，进而提高解冻品质；电压，电极形状和极距等参数对解冻特性有很大的影响。. 本项目为枸杞高压电场干燥的过程控制和预测提供实验和理论依据；对于深入理解高压电场干燥技术的参数影响特性和干燥机制有重要的理论意义。