姜片热风干燥模型适用性及色泽变化

为研究姜片的热风干燥特性，以姜片厚度、热风温度、热风风速3 个干燥条件为变量，考察其对姜片干燥特性的影响，将不同干燥条件下姜片的水分比、干燥速率进行比较并建立模型。结果表明：姜片的热风干燥以降速过程为主，而且姜片的水分比MR下降的速率随着热风温度、风速的增加而变快，随姜片厚度的增加而变慢。本实验选用常用的8 个薄层干燥模型进行拟合，经拟合后选择Modified Page模型作为姜片干燥过程的最优模型，解出模型为MR=exp[－（kt）n]，其中k=－0.023 85＋0.000 505T＋0.023 38V－0.004 993L，n=1.318 307＋0.003 016 5T－0.204 05V－0.002 859L，式中T为干燥温度（℃）；V为热风风速（m/s）；L为姜片厚度（mm）。此模型的平均R2值是0.997 9、χ2最小值是0.000 4、RMSE最小值是0.012 2。模型求解后，以模型外的实验组数据验证表现出较好的拟合度。姜片的有效水分扩散系数Deff随干燥温度、物料厚度、风速的增加而增加，且其值在1.763×10－8～1.054×10－7 m2/s之间变化，活化能为Ea=35.23 kJ/mol（R2=0.948 0）。此外还对姜片在干燥前后的色差进行了测定和分析。

Mathematical Modeling of Hot Air Drying of Ginger Slices and Their Color Changes

This research was performed to study the drying characteristics of ginger slices. Hot air drying was conducted
with different combinations of hot air temperature (60, 70 and 80 ℃), slice thickness (2, 4 and 6 mm) and air velocity (0.4, 0.8
and 1.2 m/s). Then moisture ratio (MR) and drying rate were compared under different drying conditions and modeled. The
results showed that the drying process was described as a rate-falling model. The MR of ginger slices declined faster with
increasing hot air temperature and velocity, but slower with an increase in slice thickness. The fitting of mathematical models
was conducted based on eight different thin layer models. It was found that the modified Page model was superior to other
models with an average R2 of 0.997 9, minimum χ2 of 0.000 4, and minimum RMSE of 0.012 2. The model was expressed
as MR = exp[－(kt)n], k = - 0.023 85 + 0.000 505T + 0.023 38V - 0.004 993L, n = 1.318 307 + 0.003 016 5T - 0.204 05V -
0.002 859L, where T is air temperature, V is air velocity, and L is slice thickness, showing excellent goodness-of-fit as
validated using experimental data. Effective moisture diffusion coefficient (Deff) of ginger slices varied from 1.763 × 10-8 to
1.054 × 10-7 m2/s, which was positively related to drying temperature, slice thickness and air velocity, and activation energy
was 35.23 kJ/mol (R2=0.948 0). At last, the color changes of ginger slices at different air temperatures were examined.