In this study, our aim was to investigate the effect of water quality on the sensory characteristics and flavor components of tea infusion. Raw Pu-erh tea and 14 types of brewing water were selected. Through sensory evaluation and physicochemical analysis, it was found that the pH, electrical conductivity, total dissolved solids (TDS) content, and mineral composition of brewing water were the key factors determining the flavor variation of tea infusion. Water with a high TDS content tended to enhance the richness and smoothness of tea infusion. However, excess calcium and magnesium ions inhibited the dissolution of tea polyphenols. Near-neutral water (pH 6.5–7.5), on the other hand, was more conducive to the release of amino acids and aroma compounds, contributing to the formation of a fresh and delicate flavor profile. In addition, metasilicate ions, sodium, and potassium significantly affected the synergistic effects of flavor components by altering the extraction kinetics. This research provides data to support the establishment of a “raw Pu-erh tea-water compatibility” theory. It not only guides consumers in making informed choices regarding water selection for tea brewing, but also provides valuable references for establishing a standardized brewing system and regulating tea quality.

Based on ultra-high performance liquid chromatography-triple quadrupole-tandem mass spectrometry (UPLCQQQ-MS/MS), a high throughput, sensitive and specific method to quantify three classes of phenolic compounds in tea samples was developed and validated. This method possessed good linearity, accuracy and precision, and was successfully applied to the simultaneous quantification of 90 phenolic compounds (catechins, phenolic acids, flavonoids and their glycosides) in four types of Yunnan large-leaf tea. As a result, most phenolic components were more abundant in unfermented tea (green tea and Pu’erh raw tea), while free phenolic acids, flavonoid aglycones and theaflavins were more abundant in fermented tea (black tea and Pu’erh ripe tea). By partial least squares-discriminant analysis (PLS-DA), different types of tea were clearly discriminated according to their phenolic components, and a series of chemical markers were identified.

In this study, glycerin was used instead of traditional solvents such as methanol in combination with ultrasonic treatment for the high-efficiency extraction of multiple chemical components from tea. Furthermore, a quantitative analytical method for 130 chemical components belonging to seven classes in tea and its by-products was developed using ultra-high performance liquid chromatography-triple quadrupole tandem mass spectrometry (UPLC-QQQ-MS/MS). The results showed that the extraction efficiency of glycerol was comparable to that of methanol and ethanol, and significantly better than that of water. The developed method had high sensitivity (limit of detection of 0.0001-4.3321 mg/kg) and accuracy (recoveries of 80.10%–121.12%). Appling this method to real samples, the content of each component varied greatly among different types of tea and by-products. Compared with tea samples, tea residue, a tea by-product, contained higher contents of caffeine, catechin and theanine, indicating the potential value of this by-product.