Abstract: To discern the differences in the quality of different grades (low and high) of Wuyi Rougui tea with different baking degrees (low and medium), we compared the color difference, pH, conductivity, and major taste components of the tea infusions based on physicochemical characterization and ultra performance liquid chromatography-triple-quadrupole-mass spectrometry (UPLC-TQS-MS) analysis. The results showed that the pH, conductivity and brightness of high-grade tea infusion were significantly higher (P < 0.01) than those of low-grade tea infusion, while the color saturation value (Sab) was significantly lower (P < 0.05) indicating that the brightness of high-grade tea infusion was better than that of low-grade tea infusion. The redness-greenness (a) value, yellowness-blueness (b) value, b/a, hue chroma value, hue angle value and Sab value of tea infusion varied significantly with baking degree (P < 0.01 or 0.05). The pH of high-grade tea infusion with medium baking degree was significantly lower than that of the counterpart with low baking degree (P < 0.01), and the former exhibited a reddish color while the latter was yellowish in color. The contents of seven catechins as taste active components in high-grade tea were significantly higher (P < 0.01) than those in low-grade tea. Meanwhile, the contents of gallocatechingallate, epicatechin, epigallocatechin, epigallocatechingallate and (-)-epigallocatechin3-O-(3-O-methyl) varied significantly with baking degree (P < 0.01 or 0.05). The contents of 13 amino acids were significantly higher in high-grade tea than in low-grade tea (P < 0.01 or 0.05), and significantly lower in high-grade tea with medium baking degree than in the counterpart with low baking degree (P < 0.01). The content of tyrosine was significantly lower in high-grade tea than in low-grade tea, and in low-grade tea with medium baking degree than in the counterpart with low baking degree. The content of theaflavin in high-grade tea was significantly higher (P < 0.01) than that in low-grade tea, while the contents of caffeine and rutin were significantly lower (P < 0.01) than those in low-grade tea. Therefore, high-grade tea contained more contents, which will provide a basis for the quality identification of Wuyi Rougui tea.

Key words: Wuyi Rougui tea, pH, conductivity, color parameters, taste compounds