黄芩微波热风联合干燥动力学及品质研究

Drying kinetics and quality of Scutellaria baicalensis microwave-hot air combined with drying

目的 探索黄芩Scutellaria baicalensis更优干燥方式,研究其干燥特性和干燥动力学,为提高黄芩干燥品质提供依据。方法 采用分光测色技术和HPLC法分别测定黄芩的色泽和黄芩苷含量,以干燥时间、色泽和黄芩苷含量为指标分析微波干燥、热风干燥、微波热风组合干燥3种干燥方式对黄芩干燥品质的影响,用变异系数法对各指标进行综合评分,确定更优干燥方式。探究不同微波功率密度(9、12、15 W/g)、转换点含水率(30%、40%、50%)、热风温度(50、60、70℃)对黄芩干燥特性和干燥动力学的影响。结果 相比于单一的微波干燥和热风干燥,黄芩微波热风联合干燥具有较短的干燥时间、总色差值最小为16.25±1.05、黄芩苷含量和综合质量评分最高分别为(18.88±0.30)%和88.16,说明采用微波热风联合干燥方式能有效提高黄芩的干燥品质。黄芩的干燥时间随热风温度的增大而减小,随转换点含水率和微波功率密度的增大先减小后增大。Two-term模型可以用来描述黄芩微波热风联合干燥过程。微波干燥阶段有效水分扩散系数(effective moisture diffusion coefficient,D)为4.516 9×10^(-7)~7.699 9×10^(-7)m^(2)/s,并随微波功率密度的增大而增大,远大于热风干燥阶段D。结论 微波热风联合干燥更适用于黄芩中药材的干燥加工,能有效提高黄芩的干燥品质,为微波热风联合干燥技术应用于黄芩等中药材的干燥提供了理论依据和技术指导。

Objective To explore the optimal drying method of Huangqin(Scutellaria baicalensis) and study its drying characteristics and kinetics,so as to provide basis for improving the drying quality of S.baicalensis.Methods The color and baicalin content of S.baicalensis were determined by spectrophophotometric colorimetry and HPLC,and the drying time,color and content of baicalin were used to analyze the effects of microwave drying,hot air drying and microwave-hot air combined drying on the quality of dried S.baicalensis products,and the coefficient of variation method was used to score each index comprehensively,the better drying method was determined.The effects of different microwave power densities(9,12,15 W/g),moisture content on wet basis at transfer point(30%,40%,50%) and hot air temperature(50,60,70 ℃) on the drying characteristics and kinetics of S.baicalensis were investigated.Results Compared with microwave drying and hot air drying,the microwave-hot air combined drying of S.baicalensis had shorter drying time,the minimum total color difference is 16.25 ± 1.05,the highest content of baicalin and comprehensive quality evaluation are(18.88 ± 0.30)% and 88.16,respectively,indicating that the microwave-hot air combined drying could effectively improve the drying quality of S.baicalensis.The drying time of S.baicalensis decreased with the increase of hot air temperature and first decreased and then increased with the increase of moisture content on wet basis at transfer point and microwave power density.The Two-term model can be used to describe the drying process of S.baicalensis.The D in microwave drying stage is 4.516 9 × 10^(-7)—7.699 9 × 10^(-7)m^(2)/s,and increases with the increase of microwave power density,which is much larger than that in hot air drying stage.Conclusion The microwave-hot air combined drying was more suitable for the drying of S.baicalensis,and could effectively improve the drying quality of S.baicalensis,which provides theoretical basis and technical guidance for the application of microwave-hot air combined drying technology of S.baicalensis and other Chinese medicinal materials.