School of Engineering, Taylor's University, Lakeside Campus, No. 1, Jalan Taylor's, Subang Jaya, Selangor 47500, Malaysia.
Institute of Agricultural Engineering, Wrocław University of Environmental and Life Sciences, 37a Chełmońskiego Street, 51-630 Wrocław, Poland.
Molecules. 2019 Apr 9;24(7):1397. doi: 10.3390/molecules24071397.
The preservation of active constituents in fresh herbs is affected by drying methods. An effective drying method for which is increasingly marketed as an important herbal tea remains to be reported. This study evaluated the effects of conventional and new drying technologies, namely vacuum microwave drying methods, on the antioxidant activity and yield of essential oil volatiles and phytosterols. These drying methods included convective drying (CD) at 40 °C, 50 °C, and 60 °C; vacuum microwave drying (VMD) at 6, 9, and 12 W/g; convective pre-drying and vacuum microwave finish drying (CPD-VMFD) at 50 °C and 9 W/g; and freeze-drying (FD). GC–MS revealed 33 volatiles, and 2-hexen-1-ol, 2-hexenal, 1-octen-3-ol, linalool, and benzaldehyde were major constituents. The compounds β-sitosterol and α-linolenic acid were the most abundant phytosterol and fatty acid, respectively, in fresh . The highest phenolic content was achieved with CD at 60 °C. The highest antioxidant activity was obtained with CD at 40 °C and VMD at 9 W/g. On the contrary, the highest total volatiles and phytosterols were detected with CD at 50 °C and VMD at 9 W/g, respectively. This study showed that CD and VMD were effective in producing highly bioactive . A suitable drying parameter level, irrespective of the drying method used, was an important influencing factor.
新鲜草药中活性成分的保存会受到干燥方法的影响。一种有效的干燥方法，作为一种重要的草药茶，越来越受到市场的关注，但尚未见报道。本研究评估了传统和新型干燥技术，即真空微波干燥方法，对挥发油和植物甾醇的抗氧化活性和产率的影响。这些干燥方法包括在 40°C、50°C 和 60°C 下进行的对流干燥（CD）；在 6、9 和 12 W/g 下进行的真空微波干燥（VMD）；在 50°C 和 9 W/g 下进行的预对流干燥和真空微波完成干燥（CPD-VMFD）；以及冷冻干燥（FD）。GC-MS 揭示了 33 种挥发物，2-己烯-1-醇、2-己烯醛、1-辛烯-3-醇、芳樟醇和苯甲醛是主要成分。β-谷甾醇和α-亚麻酸分别是新鲜草药中最丰富的植物甾醇和脂肪酸。在 60°C 下进行 CD 时，酚含量最高。在 40°C 下进行 CD 和在 9 W/g 下进行 VMD 时，抗氧化活性最高。相反，在 50°C 下进行 CD 和在 9 W/g 下进行 VMD 时，分别检测到最高的总挥发物和植物甾醇。本研究表明，CD 和 VMD 是生产高生物活性草药的有效方法。干燥参数水平，无论使用哪种干燥方法，都是一个重要的影响因素。
