Abstract: As a key processing craft, fixation plays a key role in the formation of green tea quality. To study the effects of fixation methods on the summer green teas, a method based on ultra high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS) combined with equivalent-quantification of the tea taste, in which caffeine, epigallocatechin gallate and sodium glutamate were used as bitter, astringent, and umami reference, respectively, was applied to investigate the difference of the chemical components and taste quality in summer green teas made by microwave fixation, rotary continuous fixation and steam fixation, respectively. Results of LC-MS analysis demonstrated that the contents of catechins, flavonol/flavone glycosides, procyanidins, theasinesins, amino acids, phenolic acids, and organic acids were significantly influenced by the fixation methods. Equivalent-quantification of the tea taste (umami, bitterness and astringency) also showed that fixation methods could change the taste quality of the summer green teas: the bitterness was higher in the green teas produced by rotary continuous fixation than by steam fixation then by microwave fixation; the astringency was higher in the green tea produced by steam fixation than by rotary continuous fixation then by microwave fixation; the umami scores did not exhibited statistical differences among these three groups of tea.

Key words: summer green teas, fixation methods, taste, chemical components, LC-MS