介电特性作用下的果蔬微波冷冻干燥行为及机理

项目名称： 介电特性作用下的果蔬微波冷冻干燥行为及机理

项目编号： No.U1204332

项目类型： 联合基金项目

立项/批准年度： 2013

项目学科： 水果、蔬菜

项目作者： 段续

作者单位： 河南科技大学

项目金额： 30万元

中文摘要： 冷冻干燥是应用极为广泛的高品质果蔬加工技术，但能耗大，成本高。微波冷冻干燥技术可大幅度缩短冷冻干燥时间，降低能耗，但在低压下极易出现放电现象，产品质量不稳定，外观品质差。前期研究发现放电现象的发生概率和原料有关，且在干燥过程中呈动态变化，因此提出原料介电特性作用下的冻干过程热电耦合理论。本课题从果蔬原料在干燥过程中的介电特性变化机理出发，研究其介电特性引起的干燥行为变化机制，进一步阐明介电行为影响下的微波谐振腔电磁场分布规律，揭示微波冻干过程中发生放电现象的机理；在考虑介电特性变化的基础上建立精确的传热传质方程，对干燥过程进行正确预测；利用低频段微波加热来进一步降低发生放电现象的可能，揭示低频微波冻干过程的干燥行为与机制。本研究为进一步推动微波冻干技术在高品质冻干果蔬加工中的实际应用提供基础理论与试验数据，对解决困扰冻干食品领域的行业难题具有实际意义。

中文关键词： 果蔬；微波冷冻干燥；冷冻干燥；介电特性；干燥

英文摘要： Freeze drying (FD) is a very widely used processing technology of fruits and vegetables, but it costs too high energy and leads to high product price. Microwave freeze drying (MFD) can greatly reduce the drying time and decrease the energy consumption. Otherwise it also easily leads to plasma discharge and instable product quality with bad appearance because of low pressure condition. It was found that there were relationships between probability of occurrence of corona and materials, which showed a dynamic change characteristic. As a result, a thermoelectric coupling theory under the dielectric property effects of materials was brought up. In this project, based on the dielectric property change mechanism, the drying behavior change mechanism during MFD will be investigated. Further more, the distribution of electromagnetic field in the microwave resonance cavity under the dielectric property effect also will be clarified, and the mechanism of plasma discharge phenomenon during MFD process also will be explained. Besides, accurate heat and mass transfer equations will be set up based on consideration of the dielectric property changes in order to forecast the MFD process. Additionally, low frequency microwave will be introduced to reduce the probability of occurrence of corona, and then the dryng behavior and

英文关键词： Vegetables and fruits；Microwave freeze drying；Freeze drying；Dielectric property；Drying