三七主根微波真空-热风分段式干燥特性及品质分析

Characteristics and quality analysis of main roots of Panax notoginseng(Burk.)F.H.Chen by microwave vacuum-hot air segmented drying

为研究三七主根微波真空-热风分段式干燥特性及品质,探讨不同功率密度(0.50 W/g、0.75 W/g、1.00 W/g、1.50 W/g)、腔室压力(1 kPa、3 kPa、5 kPa、10 kPa)和温度上限(45℃、50℃、55℃)对三七主根干燥特性及有效水分扩散系数的影响,建立分段式干燥拟合模型,并对比分析三七品质的变化。结果表明,三七主根微波真空-热风分段式干燥主要分为减速阶段和恒速阶段,恒速阶段发生在干基含水率从1.0 g/g降至0.5 g/g阶段。三七主根干燥过程中微波真空阶段的有效水分扩散系数(D_(eff))为7.84×10^(-10)~1.80×10^(-9)m^(2)/s,并且随着温度上限、功率密度的增大及腔室压力的降低而增大,热风干燥阶段的D_(eff)为1.45×10^(-10)~6.82×10^(-10)m^(2)/s。对干燥过程进行分段拟合,发现Weibull模型能更好地预测三七主根微波真空-热风分段式干燥规律。与热风对照组相比,微波真空-热风分段式干燥可缩短干燥时间44.6%~60.0%,其三七干制品总皂苷含量最高为10.2%,其应用具有较好的可行性及优势。

To investigate the characteristics and quality of microwave vacuum-hot air segmented drying of Panax notoginseng main roots,effects of different power densities(0.50 W/g,0.75 W/g,1.00 W/g and 1.50 W/g),chamber pressures(1 kPa,3 kPa,5 kPa and 10 kPa)and upper temperature limits(45℃,50℃and 55℃)on the drying characteristics and effective moisture diffusion coefficient of P.notoginseng roots were discussed.Segmented drying fitting models were established,and the changes of P.notoginseng qualities were compared and analyzed.The results suggested that the microwave vacuum-hot air segmented drying of P.notoginseng main roots was mainly in the stages of falling rate and constant rate.The constant rate stage occurred when the moisture content of the dry basis dropped from 1.0 g/g to 0.5 g/g.During the microwave vacuum stage of drying process,the effective moisture diffusivity coefficient(D_(eff))was between 7.84×10^(-10)m^(2)/s and 1.80×10^(-9)m^(2)/s,which added with the increase of temperature upper limit,power density and the decrease of chamber pressure.The D_(eff) of the hot air drying stage was between 1.45×10^(-10)m^(2)/s and 6.82×10^(-10)m^(2)/s.Through segmental fitting of the drying process,it was found that the Weibull model could better predict the law of microwave vacuum-hot air sectional drying of P.notoginseng main roots.Compared with the hot air control group,it could be seen that microwave vacuum-hot air drying had shortened the drying time by 44.6%to 60.0%,and the saponins content of P.notoginseng dry products reached 10.2%,which had better feasibility and advantages.