Tea is a popular beverage over the world for centuries. It is well known that tea has various health benefits such as anti-tumor, antioxidation, antiphlogosis as well as prevention of cardiovascular disease, etc. Phytochemicals in tea leaves are the contributors to the excellent bioactivities of tea. Therein, flavonoids were the most potent compounds. Thousands of pioneer work had been made to investigate the potential of tea flavonoids as candidates. This review sorted the literature published in recent 5 years. In view of processing method, basic manufacturing procedures for the traditional types of tea were described. Research progress and functionality of tea flavonoids were discussed according to chemical structures. Fruitful research results about tea flavonoids were summarized and refined, and in-depth cognition of tea flavonoids would be obtained. We also point out the forthcoming orientation for the study on tea flavonoids based on our own understanding and consideration.

• Widely target metabolomics was used to investigate the metabolites of green teas. • Heat-conduction drying could produce much more abundant volatile compounds. • Hot-air drying could reduce amino acids, flavonols but raise flavonoid glycosides.

Combined with the unique processing technology of oolong tea, oolong tea with stem processing has a better flavor compared to oolong tea without stem processing. However, there is currently no available evidence to support the contribution of stems to the taste quality of oolong tea. In this study, the electronic tongue, sensory evaluation method combined with liquid chromatography, and gas chromatography–mass spectrometry were used to explore the influence of the presence of stems on the flavor substances and aroma of oolong tea during processing. The results showed that the presence of stems significantly increased the umami taste of oolong tea (p < 0.05), and the content of seven free amino acids (p < 0.05), including theanine (53.165 μg/mL) and aspartic acid (3.190 μg/mL), two umami-related amino acids, significantly increased. Moreover, the content of nerolidol (2.598 μg/g) in aroma components was significantly increased. This study identifies the contribution of stems to oolong tea quality during processing.

Combined withering and shaking processes are key steps in the formation of characteristic floral and fruity aromas in black teas. However, the effect of the sequencing of withering and shaking on volatile compounds and aroma formation in black tea has not been evaluated to date. This study used headspace solid-phase microextraction and gas chromatography-tandem mass spectrometry to detect volatile compounds in black teas after withering-shaking and shaking-withering processing. Five main differentially volatile components were screened out by partial least squares discriminant analysis and odor activity value analysis, which were 3-carene, geraniol, β-myrcene, τ-cadinol, and β-ionone. Additionally, sensory evaluation showed black tea produced by withering-shaking was fruitier, while shaking-withering produced a more floral tea. This study provides a theoretical basis for the discrimination of aroma characteristics of black tea processed by shaking, as well as a technical guide for the precise production of black teas with different floral-fruity aroma biases.