Trirattanapikul W, Phoungchandang S
Department of Food Technology, Faculty of Technology, Khon Kean University, 123 Mittapab Road, Khon Kaen, 40002 Thailand.
J Food Sci Technol. 2014 Dec;51(12):3623-34. doi: 10.1007/s13197-012-0876-8. Epub 2012 Nov 9.
The appropriate stage of maturity of Centella asiatica (L.) Urban leaves was investigated. Mature leaves with large diameter contained high total phenolics and % inhibition. Microwave blanching for 30 s retained the highest total phenolics and the microwave blanching for 30 s and 45 s retained the highest % inhibition. Modified Henderson and Modified Chung-Pfost models showed the best fit to both fresh and blanched leaves for equilibrium moisture content, Xe = f(RHe, T) and equilibrium relative humidity, RHe = f(Xe, T), respectively. The Modified Page model was the most effective model in describing the leaf drying. All drying was in the falling rate period. The drying constant was related to drying air temperature using the Arrhenius model. Effective moisture diffusivities increased with increasing temperature and blanching treatments as well as dehumidification by heat pump-assisted dehumidified dryer. The heat pump-assited dehumidified drying incorporated by the microwave blanching could reduce the drying time at 40 °C by 31.2 % and increase % inhibition by 6.1 %. Quality evaluation by total phenolics, % inhibition and rehydration ratio showed the best quality for C. asiatica leaves pretreated by microwave blanching and dried at 40 °C in heat pump-assisted dehumidified dryer.
对积雪草（Centella asiatica (L.) Urban）叶片的适宜成熟阶段进行了研究。直径较大的成熟叶片含有较高的总酚含量和抑菌率。微波漂烫30秒能保留最高的总酚含量，微波漂烫30秒和45秒能保留最高的抑菌率。修正的亨德森模型和修正的钟-普福斯特模型分别对新鲜叶片和漂烫叶片的平衡水分含量Xe = f(RHe, T)和平衡相对湿度RHe = f(Xe, T)拟合效果最佳。修正的佩奇模型是描述叶片干燥最有效的模型。所有干燥过程均处于降速阶段。利用阿伦尼乌斯模型将干燥常数与干燥空气温度相关联。有效水分扩散率随温度升高、漂烫处理以及热泵辅助除湿干燥机的除湿作用而增加。结合微波漂烫的热泵辅助除湿干燥可使40℃时的干燥时间缩短31.2%，抑菌率提高6.1%。通过总酚含量、抑菌率和复水率进行的品质评价表明，经微波漂烫预处理并在热泵辅助除湿干燥机中40℃干燥的积雪草叶片品质最佳。
