Effects of Various Drying Parameters on the Volatile and Non-Volatile Compositions of ‘Qiancha 1’ White Tea

Le résumé fourni par la source

'Qiancha 1' is an excellent raw material for manufacturing white tea. The effects of different drying parameters on the quality performance of 'Qiancha 1' white tea remain poorly understood, which restricts the precise regulation of the quality of 'Qiancha 1' white tea. In this research, we systematically investigated the influence of drying temperature (65 °C, 75 °C, and 90 °C) and drying duration (1 h, 2 h, and 3 h) on its non-volatile and volatile compositions, using sensory evaluation, E-tongue, and non-volatilomic and volatilomic analyses. The results showed that the tea sample dried at 65 °C for 3 h had a sweet, mellow, and fresh flavor and scored 95 points, but high-temperature drying (90 °C) could promote increased bitterness and decreased sweetness. High-temperature drying was closely related to a caramel-like and milk-like flavor, which promoted an increase in the content of terpenoids, heterocycle compounds, and esters. During drying, the flavonoid and phenolic acid content increased markedly, contributing to bitterness and astringency, while nucleotides, amino acids, and their derivatives decreased, leading to a reduced umami intensity. A total of 37 key taste-active metabolites were identified, including bitter compounds (e.g., alkaloids), sweet compounds (e.g., phenolic acids), and umami compounds (e.g., nucleotides), whose dynamic changes directly influenced the taste profile of white tea. High-temperature drying promoted an increase in the content of volatile metabolites, such as terpenoids, heterocyclics, and esters, while low-temperature and long-duration drying was beneficial for preserving volatile metabolites like heptanal. 2-Methoxy-3-(1-methylethyl)-pyrazine was determined as the volatile compound with the highest rOAV, providing a sweetness and caramel-like flavor. Overall, the metabolomic analysis revealed that the content of flavonoids and phenolic acids increased after the drying process, which was related to the bitter and astringent taste of the tea liquor. The content of nucleotides, amino acids, and their derivatives decreased after drying, which caused the umami of the tea liquor to weaken. This study provides a theoretical basis for the optimization of the 'Qiancha 1' white tea drying process.

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