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To explore the relationship between the moisture content of withered tea leaves and their physical properties (i.e., elasticity, plasticity, flexibility, and texture) during withering, texture analyzer was employed to test the elasticity and flexibility of withered tea leaves with different moisture contents. The texture was evaluated by computer vision technology. The withered tea leaves with different moisture contents were used to process congou black tea, which was then subjected to sensory evaluation. Results showed that good elasticity, optimal flexibility, and plasticity were achieved when the moisture content of the withered tea leaves of Fudingdabai comprising two leaves and one bud varied arranging from 65.51 to 61.48%. The sensory evaluation of congou black tea revealed that moderate withering was better than long-term withering and that both moderate and long-term withering were better than no withering during processing. The moisture content was significantly correlated with the flexibility and plasticity of the withered tea leaves. Fresh tea leaves undergoing moderate withering with moisture content of 65.51-61.48% to process congou black tea, good tea shape and liquor color were achieved. This study provided new evidence that the moisture content of withered tea leaves significantly affected the quality of black tea., (© 2019 Wiley Periodicals, Inc.)

In this study, metabolomics and proteomics were performed to investigate the fluctuations of non-volatile compounds and proteins in tea leaves from three tea cultivars with varying colours during withering. A total of 2798 compounds were detected, exhibiting considerable variations in amino acids, phenylpropanoids, and flavonoids. The ZH1 cultivar displayed increased levels of amino acids but decreased levels of polyphenols, which might be associated with the up-regulation of enzymes responsible for protein degradation and subsequent amino acid production, as well as the down-regulation of enzymes involved in phenylpropanoid and flavonoid biosynthesis. The FUD and ZH1 cultivars had elevated levels of flavanols and flavanol-O-glycosides, which were regulated by the upregulation of FLS. The ZJ and ZH1 cultivars displayed elevated levels of theaflavin and peroxidase. This work presents a novel investigation into the alterations of metabolites and proteins between tea cultivars during withering, and helps with the tea cultivar selection and manufacturing development. [Display omitted] • Multi-omics study on tea leaves from three different tea cultivars with distinct colours during withering. • The composition and contents of non-volatile chemicals varied with tea cultivars and withering times. • The amino acids biosynthesis was increased and the polyphenols biosynthesis was decreased in the ZH1 cultivar. • The flavonoid biosynthesis was increased in the FUD and ZJ cultivars during withering. • The levels of PODs and PPOs were elevated in the ZJ and ZH1 cultivars during withering. [ABSTRACT FROM AUTHOR]

Withering is a necessary step to improve the flavors during the manufacturing of black tea. Fresh tea leaves of Fuding Dabai were subjected to withering (kept for 0–28 h at room temperature of 25 °C) to observe corresponding morphological changes. In addition, dynamic changes in proteinaceous amino acids, especially taste-related proteinaceous amino acids and their corresponding driving proteins, were investigated using targeted metabolomics and data-independent acquisition (DIA) proteomics. The results indicated that tea leaves gradually withered and shrunk, and their color deepened with the extension of withering time. Furthermore, the contents of umami amino acids were always higher during the withering process. Sweet and bitter amino acids exhibited a significant cumulative effect at the middle and late withering stages. A total of 31 driving proteins were detected that were involved in the metabolic regulation of Ser, Thr, Phe, Trp, and His amino acids. The functional analysis of 776 differential expressed proteins revealed that the tea leaf cells maintained the maximum possible cellular activity during the withering process, and the toxins were decomposed at the end of withering. These findings can provide the metabolic basis for room temperature withering during black tea processing to further enhance the quality of tea. • Targeted metabolomics can reveal the profile of proteinaceous amino acids in black tea during withering. • Data-independent, acquisition-based quantitative proteome profiling of black tea was performed during withering. • A combination of metabolomics and proteomics can decipher the driving proteins of sweet and bitter amino acids. [ABSTRACT FROM AUTHOR]