苦瓜微波-热风振动床干燥湿热特性与表观形态研究  

Moisture and Heat Characteristics and Apparent Form of Balsam Pears in Microwave-Hot-airflow Vibrating Bed Drying

作　　者：吕豪[1] 吕黄珍[2] 杨炳南[2] 吕为乔[1] 杜志龙[2] LüHao;L Huangzhen;YANG Bingnan;LüWeiqiao;DU Zhilong(College of Engineering,China Agricultural University,Beijing 100083,China;Chinese Academy of Agricultural Mechanization Sciences,Beijing 100083,China)

机构地区：[1]中国农业大学工学院,北京100083 [2]中国农业机械化科学研究院,北京100083

出　　处：《农业机械学报》2020年第4期373-381,共9页Transactions of the Chinese Society for Agricultural Machinery

基　　金：广东省科技计划项目(2018B020241003-10);国家重点研发计划项目(2017YFD0400900)。

摘　　要：为探索热风对苦瓜片微波干燥特性、湿热特性与表观形态的影响,利用微波-热风振动流化床干燥机,研究了新鲜苦瓜片在不同微波-热风组合方式下的干燥动力学特性、热像变化、水分状态分布、色泽以及微观结构的变化。试验结果表明:热风对微波振动流化床干燥有显著影响,微波0.6 W/g、微波0.6 W/g+热风60℃+风速3 m/s、微波0.6 W/g+热风70℃+风速6 m/s比单独热风70℃+风速3 m/s的干燥时间分别缩短56.4%、70.5%和75.6%。在表观形态上,单独热风干燥的脱水苦瓜片与新鲜苦瓜片色泽最为接近,两组微波-热风组合干燥所得样品色泽优于单独微波干燥。在湿热特性上,微波-热风组合干燥后期物料温度均匀性显著优于单独微波干燥,4种干燥方式下NMR波谱下的水分信号逐渐降低,且主峰向左移,水分的活跃程度降低,MRI信号显示,热风能改善微波干燥过程中水分分布均匀性。扫描电镜观测表明,单独热风干燥对保持脱水苦瓜片细胞完整性效果最明显,微波-热风组合干燥的细胞完整性显著优于单独微波干燥。微波-热风组合振动流化床干燥工艺在保证被干物料品质前提下还极大提高了物料干燥效率,缩短了干燥时间。Aiming to explore the effect of wet-thermal characteristics and morphology of hot-airflow on the microwave vibrating fluidized bed drying,the drying kinetics,thermal image changes,water distribution,color and microstructure of fresh bitter gourd slices under four microwave-hot-airflow drying modes were studied by microwave-hot-airflow vibrating dryer. The results showed that the hot-airflow temperature had a significant effect on microwave-hot-airflow vibrating fluidized bed drying. The drying time of hot-airflow drying was slower,and the drying time of microwave drying alone,microwave power 0. 6 W/g + hotairflow 60℃ + air-speed 3 m/s,microwave power 0. 6 W/g + hot-airflow 70℃ + air-speed 6 m/s was56. 4%,70. 5% and 75. 6% shorter than that of the hot-airflow drying with hot air 70℃ + air-speed 3 m/s.The color of dehydrated product by hot-airflow was closest to fresh balsam pear slices,the color of dehydrated product by microwave-hot-airflow combination drying was better than that of microwave drying alone. The temperature uniformity of microwave-hot-airflow combination drying was significantly better than that of microwave drying alone and hot-airflow drying alone. The moisture signal was gradually decreased and the main peak was moved to the left under NMR spectrum by four drying modes. The MRI signal showed that hot-airflow had a significant effect on the uniformity of water distribution during microwave drying. Scanning electron microscopy observation showed that the hot-airflow drying was the most obvious to maintain the cell integrity of dehydrated product,and the cell integrity of microwave-hotairflow drying was better than that of microwave alone. The study provided a theoretical basis for the processing technology selection of dehydrated product.

关 键 词：苦瓜 微波干燥 热风干燥 水分流动特性 振动床 

分 类 号：TS255.36[轻工技术与工程—农产品加工及贮藏工程]