工夫红茶真空脉动干燥特性及数学模型研究

Drying characteristics and models of black tea in pulsed vacuum dryer

为研究工夫红茶真空脉动干燥特性与数学模型,本文采用不同干燥温度（60℃、80℃、100℃、120℃）、真空度（50kPa、65kPa、80kPa、95kPa）、真空保持时间（0s、30s、60s、90s）对工夫红茶进行真空脉动干燥。研究结果表明：干燥温度越高,干燥时间越短,干燥速率越大;真空度增大,真空保持时间缩短,干燥速率有增大的趋势。工夫红茶的水分有效扩散系数为（0.729 5～2.553 3）×10^-9 m^2/s,平均活化能为23.10kJ/（mol·K）。采用决定系数R^2和卡方χ^2对6个干燥模型进行评价,结果表明Page模型最优,能够准确预测干燥过程中水分比的变化。与热风干燥相比,真空脉动干燥工夫红茶汤色得分明显较高,经提香处理后其感官总分优于热风干燥。

In order to study drying characteristics and models of black tea in pulsed vacuum dryer, black tea was investigated in differ- ent temperatures （60℃, 80℃, 100℃, 120℃）, vacuums （50kPa, 65kPa, 80kPa, 95kPa）, and vacuum holding times （0s, 30s, 60s, 90s）. The results show that, the higher the drying temperature, the shorter the drying time and the greater the drying rate; Increasing the degree of vacuum and shorting the vacuum holding time, the drying rate tends to increase. Moisture effective diffusion coefficient of black tea is （0. 729 5～2. 553 3）× 10^-9m^2/s. The average activation energy is 23.10kJ/（mol · K）. According to the statistical parameters, such as determination coefficient R^2 and chi-square χ^2, the page equation is the best model. It can accurately predict the moisture ratio changes in the drying process. Compared with those of hot-air drying black, liquor colors of pulsed vacuum drying black tea were significantly improved. The sensory score of aroma-improving pulsed vacuum drying black tea was better than that of hot-air drying black tea.