Search

This study investigated the changes of main quality components and the effect of bioactivities of black tea during a manufacturing process that adds to enzymatic treatment. It used black tea harvests in summer and autumn for manufacturing and analyzed the number of main quality components and bioactivities of the black tea produced by treating cellulase during rolling and polyphenol oxidase (PPO) and peroxidase (POD) during fermentation. The results found that the contents of total catechins (TC), total polyphenols (TP), reducing sugars (ReS), and individual catechins in the tea infusions of summer and autumn black tea that were obtained during enzymatic treatments decreased significantly (p < 0.05). However, the content of free amino acid (FAA), the tea quality parameter such as the total liquor color (TLC), the briskness index (BI), and the tea pigments including total theaflavin (TF), thearubigens (TR), TRSI, and TRSII all increased significantly (p < 0.05). Moreover, the biological activity enhanced black tea's antioxidant and metabolic capacity with enzymatic treatments were proved by in vitro experiments. The results of this study contribute to gaining further knowledge on how black tea's quality and potential health benefits are maximized by using exogenous enzyme addition methods in the manufacturing process preparation. • The quality is significantly enhanced by enzymatic treatment in the manufacturing process of black tea. • TF and TR improved bioactivities more than total polyphenol, free amino acids, and catechin. • Enzymatic treatment of black tea may effectively increase TLC levels in tea liquor and improve the quality of black tea brew. [ABSTRACT FROM AUTHOR]

Shaken black tea (SBT) is a new type of black tea that combines the traditional black tea processing technology with the shaking process of oolong tea. In this study, non-targeted metabolomics analysis based on ultra-high-pressure liquid chromatography quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS) was applied to comprehensively analyze the non-volatile metabolites of SBT during the manufacturing process. Using multivariate statistical analysis, 93 compounds were screened as differential compounds. During the whole process of SBT, amino acids, dipeptides, theaflavins and lipids contents showed significant increases, while that of catechins and procyanidin C1 significantly decreased. Compared with fresh leaves, the content of proteinaceous amino acids (PAAs) in the dried black tea increased 1.61-fold, and total catechins decreased to 7.25%. The results of hierarchical clustering analysis (HCA) showed that fermentation is the key process that causes the variations of these metabolites, followed by drying and shaking. The biosynthesis metabolism of amino acids, flavonoids and linoleic acid are abundant, mainly due to the stress response of fresh tea leaves to dehydration and mechanical damage during shaking processing. It is beneficial to explore the quality formation during the production of SBT through comprehensive analysis of the changes in metabolites. • Fermentation led to significant changes in metabolites, followed by drying, shaking. • Shaking process promoted the accumulation of amino acids, dipeptides and theaflavins. • Remarkable increase of dipeptides is mainly in the fermentation and drying process. • Variation of taste compounds, amino acids, flavonoids, and dipeptides, were studied. • Metabolic pathway of key compounds like amino acids, flavonoids, lipids, were revealed. [ABSTRACT FROM AUTHOR]