XUE Jingjing, LI Shan, XU Zhijie, LI Yanbing, XU Hang, WU Wei, SUN Zhengguang, BAI Bing, YANG Jing
The study investigated the impact of different drying methods, including hot air drying at 40 ℃ (HAD 40 ℃), hot air drying at 50 ℃ (HAD 50 ℃), hot air drying at 60 ℃ (HAD 60 ℃), microwave vacuum drying (MVD), vacuum freeze drying (VFD), and natural air drying, on the drying kinetics and volatile compositions of Strobilanthes tonkinensis Leaves.The drying processes of the six drying methods were simulated using a thin-layer drying model.The impact of these different drying methods on the volatile components was assessed through the utilization of an electronic nose (E-nose) in conjunction with headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS).Additionally, organoleptic evaluations were conducted to determine the most suitable drying method for S. tonkinensis leaves.The results showed that the drying rate was highest for MVD and lowest for natural drying, with the Page model demonstrating the best fit for simulating the drying kinetics of S. tonkinensis leaves.Significant variations were observed in the types and concentrations of volatile components among different drying methods, aligning closely with the outcomes obtained from the electronic nose analysis.A total of 61 volatile components across 9 types were identified in the six drying methods, with 42, 27, 28, 25, 38, and 49 components detected in HAD 40 ℃, HAD 50 ℃, HAD 60 ℃, MVD, VFD, and natural drying, respectively.Significant losses of volatile components were observed in HAD 50 ℃, HAD 60 ℃, and MVD.HAD 50 ℃, MVD, VFD, and natural drying methods exhibited better preservation of alcohols and ketones.HAD 40 ℃ had the highest nitrogen compound content.In sensory evaluation, HAD 40 ℃ received the highest total sensory score, displaying a bright yellow-green color in the tea broth, a pure aroma with a distinct glutinous rice note, a mellow taste, and a lingering aftertaste.PLS-DA identified 20 distinct volatile components, enabling effective differentiation among the various drying methods applied to S. tonkinensis leaves.The study offers a theoretical foundation for the optimized drying and processing of S. tonkinensis leaves.