Changes in Aromatic and Functional Components of Finished Yunnan Black Tea Roasted under Different Conditions
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Abstract:
To improve Yunnan black tea quality, finished Yunnan black tea was roasted at different temperatures for varying durations. The aromatic components of the Yunnan black tea were detected using simultaneous steam distillation extraction-gas chromatography-mass spectrometry, whereas other functional components were determined using high-performance liquid chromatography. Changes in the primary aromatic and functional components of the Yunnan black tea roasted under different conditions were also studied. A total of 65 kinds of volatile substances were detected in the roasted Yunnan black tea. The contents of the primary aromatic components benzyl alcohol and geraniol increased significantly when the tea was roasted at 70 ℃ and 90 ℃ for 1~4 h. Similarly, the contents of indole and pyridine reached their maxima when the tea was roasted at 110 ℃ for 4 h. The content of pyrazine increased rapidly with time at 130 ℃. In contrast, tea polyphenol content decreased as the roasting temperature and time increased. Regardless of the roasting temperature, the gallic acid content increased gradually with time. The content of catechin peaked when the tea was roasted at 130 ℃ for 2.5 h. Furthermore, the contents of epigallocatechin gallate and three other substances increased after the tea was roasted at 70 ℃ and 90 ℃ for 1~2.5 h. In summary, roasting at 70 ℃ and 90 ℃ for 1~2.5 h enhanced the aroma of the finished tea and induced conversion of tea polyphenol to gallic acid and catechin. This method can enhance the effectiveness of Yunnan black tea as a health product.
