Characterisation of the Convective Hot-Air Drying and Vacuum Microwave Drying of Cassia alata: Antioxidant Activity, Essential Oil Volatile Composition and Quality Studies
Characterisation of the Convective Hot-Air Drying and Vacuum Microwave Drying of Cassia alata: Antioxidant Activity, Essential Oil Volatile Composition and Quality Studies
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DOI：
10.3390/molecules24081625
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发表时间：
2019-04-02
期刊：
影响因子：
4.6
通讯作者：
Lech, Krzysztof
中科院分区：
文献类型：
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作者：
Chua, Lisa Yen Wen;Chua, Bee Lin;Lech, Krzysztof
通过去除水分来保存决明子中的有效成分是生产具有高抗氧化活性的最终产品的关键。本研究旨在确定不同干燥方法和干燥条件对凤眼莲的抗氧化活性、挥发物和植物甾醇含量的影响。干燥方法为40℃、50℃和60℃下的对流干燥(CD)；冷冻干燥；6、9和12W/g的真空微波干燥(VMD)；50℃和9W/g的两级对流预干燥(CPD-VMFD)。Cd在40℃时具有最高的抗氧化活性、TPC和挥发物浓度，GC-MS分析鉴定出51种挥发物，它们主要存在于所有样品中，但数量上有变化。新鲜鱼腥草中的主要挥发物为2-己烯醛(60.28 mg 100g(-1)db)、1-己醇(18.70 mg 100 g(-1)db)和水杨酸(15.05 mg 100 g(-1)db)。新鲜样品中植物甾醇的含量为3647.48 mg 100g(-1db)，新鲜样品和干燥样品中的主要植物甾醇为-谷甾醇(1162.24 mg 100g(-1db))。与50℃下的Cd相比，CPD-VMFD能有效地确保较高的植物甾醇含量。最终推荐的适宜干燥方法是40℃下的Cd。
The preservation of active constituents in Cassia alata through the removal of moisture is crucial in producing a final product with high antioxidant activity. This study aims to determine the influences of various drying methods and drying conditions on the antioxidant activity, volatiles and phytosterols content of C. alata. The drying methods used were convective drying (CD) at 40 degrees C, 50 degrees C and 60 degrees C; freeze drying; vacuum microwave drying (VMD) at 6, 9 and 12 W/g; and two-stage convective pre-drying followed by vacuum microwave finish drying (CPD-VMFD) at 50 degrees C and 9 W/g. The drying kinetics of C. alata are best described by the thin-layer model (modified Page model). The highest antioxidant activity, TPC and volatile concentration were achieved with CD at 40 degrees C. GC-MS analysis identified the presence of 51 volatiles, which were mostly present in all samples but with quantitative variation. The dominant volatiles in fresh C. alata are 2-hexenal (60.28 mg 100 g(-1) db), 1-hexanol (18.70 mg 100 g(-1) db) and salicylic acid (15.05 mg 100 g(-1) db). The concentration of phytosterols in fresh sample was 3647.48 mg 100 g(-1) db, and the major phytosterols present in fresh and dried samples were -sitosterol (1162.24 mg 100 g(-1) db). CPD-VMFD was effective in ensuring the preservation of higher phytosterol content in comparison with CD at 50 degrees C. The final recommendation of a suitable drying method to dehydrate C. alata leaves is CD at 40 degrees C.