绿茶微波真空干燥特性及动力学模型

Drying characteristics and dynamics model of green tea by microwave vacuum drying

为了解茶叶在微波真空干燥过程中水分的变化规律,以绿茶为原料,进行了微波真空干燥试验。通过绘制干燥曲线和失水速率曲线,研究相对压力、比功率对绿茶微波真空干燥特性的影响,并建立干燥动力学模型,量化比功率与干燥时间、含水率之间的关系。结果表明:绿茶微波真空干燥过程按失水速率快慢可分为加速和降速2个阶段,无明显恒速干燥阶段;随着相对压力降低,干燥时间缩短,但-80kPa后继续降低相对压力对含水率变化影响不显著;比功率越大干燥时间越短;绿茶微波真空干燥的动力学模型满足Page方程,该模型可较好地描述含水率随干燥时间、比功率的变化关系。试验结果为实现绿茶的可控制工业化生产提供了技术依据。

The experiments of microwave vacuum drying of green tea were conducted for study rules of moisture change during drying process.With drying curves and dehydrating rate curves,the effect of relative pressure and specific power on microwave vacuum drying characteristics of green tea was studied,and a drying dynamics model was established.The results showed that,according to the dehydrating rate,the process of microwave vacuum drying for green tea could be divided into two stages—accelerated phase and decelerated phase,without obvious constant-speed phase.The drying time decreased with relative pressure decreasing,however,change of moisture content was indistinctive when relative pressure kept decreasing beyond-80 kPa,and the drying time decreased with specific power increasing.The dynamics model of microwave vacuum drying for green tea agreed with Page equation,which could be used for describing the relationship among moisture content,drying time and specific power.The experiment results can provide a technical basis for controllable industrialization production of green tea.