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Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Steamed green tea has unique characteristics that differ from other green teas. However, the alteration patterns of non-volatile metabolites during steamed green tea processing are not fully understood. In this study, a widely targeted metabolomic method was employed to explore the changes in non-volatile metabolites during steamed green tea processing. A total of 735 non-volatile compounds were identified, covering 14 subclasses. Of these, 256 compounds showed significant changes in at least one processing step. Most amino acids, main catechins, caffeine, and main sugars were excluded from the analysis. The most significant alterations were observed during steaming, followed by shaping and drying. Steaming resulted in significant increases in the levels of most amino acids and their peptides, most phenolic acids, most organic acids, and most nucleotides and their derivates, as well as some flavonoids. Steaming also resulted in significant decreases in the levels of most lipids and some flavonoids. Shaping and drying caused significant increases in the levels of some flavonoids, phenolic acids, and lipids, and significant decreases in the levels of some amino acids and their peptides, some flavonoids, and some other compounds. Our study provides a comprehensive characterization of the dynamic alterations in non-volatile metabolites during steamed green tea manufacturing. [ABSTRACT FROM AUTHOR]

Withering process is one of the most crucial steps in Keemun black tea (KBT) manufacturing, which is the foundation of quality formation. This study investigated the effects of conventional static withering and innovative dynamic withering on the volatile and nonvolatile compounds of KBT. Overall, 79 volatile compounds were identified in five tea samples (FL: fresh leaf for control; SW7h, SW15h: leaves of static withering 7 h and 15 h; and DW7h, DW15h: leaves of dynamic withering 7 h and 15 h) by using HS-SPME/GC-MS. Orthogonal projections to latent structures discriminant analysis (OPLS-DA) were used to classify samples, and 36 key markers in volatile compounds were selected. Quantitative descriptive analysis (QDA) of KBT aroma showed that in dynamic withering, dense, floral and fruity aroma were significantly improved. The 14 odor-active compounds were speculated as the cause of QDA differences in aroma between dynamic and static withering. Meanwhile, theaflavins were generated and accumulated earlier in dynamic withering. Notably, the contents of aspartic acid, serine, glycine, arginine, cysteine, methionine, lysine, isoleucine, and leucine significantly increased after dynamic withering. Our study provides a comparative investigation metabolite of dynamic and static withering processes, offering innovative dynamic withering methods to improve the quality of KBT. • A novel dynamic withering process of Keemun black tea is firstly investigated. • The changes of metabolite content in different withering processes were compared. • Fourteen key markers as odor-active compounds (OAV>1) were identified. • Dynamic withering improved the floral and fruity aroma of Keemun black tea. • Amino acids and theaflavins significantly increased after dynamic withering. [ABSTRACT FROM AUTHOR]