干燥方式对铁皮石斛品质的影响

本实验研究了铁皮石斛热风干燥、微波间歇干燥和真空冷冻干燥3种干燥方式及其工艺参数对铁皮石斛色差及主要活性成分含量的影响。结果表明:铁皮石斛热风干燥的最佳条件为90℃干燥4 h,微波间歇干燥的最佳条件为550 W、间隔时间30 s、干燥48 min,在这两种干燥条件下,微波间歇干燥后的铁皮石斛总酚及多糖的含量明显高于热风干燥,但二者黄酮含量无明显差异,说明微波间歇干燥可以有效保留总酚及多糖类物质;真空冷冻干燥所需时间为11 h,干燥后所得铁皮石斛多糖含量较高;在最佳工艺条件下,铁皮石斛平均干燥速率和最大干燥速率均为:微波间歇干燥>热风干燥>真空冷冻干燥,成品色泽以真空冷冻干燥更佳。微波间歇干燥具有速率快、活性成分破坏小的优势,具有更好的推广意义。

Effect of Different Drying Methods on Quality of Dendrobium officinale Stems

In this study, we compared the effect of three different drying methods: hot-air drying, intermittence microwave drying and vacuum freeze drying on the color and main bioactive components of Dendrobium officinale stems. The results showed that the best hot-air drying conditions were 90 ℃ and 4 h, the best microwave drying conditions were irradiation at 550 W for 48 min with 30 s intervals, and the best vacuum freeze drying duration was 11 h. The intermittence microwave dried sample had significantly higher contents of total polyphenols and polysaccharides than did the hot-air dried one, while no marked difference in total flavonoid content existed between them, suggesting that both classes of compounds could be preserved better during intermittence microwave drying. Vacuum freeze drying process was most effective in preserving the polysaccharides and color of Dendrobium officinale stems. Under the best drying condition, the maximum and average drying rate followed a decreasing order of intermittence microwave drying > hot-air drying > vacuum freeze drying. From the above results, we conclude that intermittence microwave drying has the greatest potential for application due to the advantages of fast drying rate and less destruction of bioactive phytochemicals.