Study Of The Taste Quality Of Green Tea Based On Metabolomics Analysis

Taste,which is the result of interaction of various components of green tea, is one of the most important elements for evaluating the quality of green tea. Compounds responsible for taste quality include tea polyphenols, amino acids, alkaloid, soluble saccharides, organic acids and so on. Among these compounds, tea polyphenols and caffeine are principal source of astringency and bitterness, and amino acids provide umami taste for green tea. Although relationship between other chemical constituents and taste quality still needs further investigation. In this study,we applied metabolomics analysis using ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry and equivalent-quantification evaluation method to investigate the effects of plucking seasons and fixation methods on metabolite profiles and taste quality of green tea. The results were listed as follows: 1. Metabolomics analysis based on ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry was applied to the quantification and qualification study of tea, and I improved equivalent-quantification evaluation method to better quantify the taste quality(bitterness, astringency and umami) of green tea. 2. There was significant difference among green tea plucked in different seasons both in the taste quality including astringency, bitterness and umami, and composition of chemical components and content. Result of equivalent-quantification evaluation showed that, compared with spring tea samples, there was great decrease in umami taste and increase in astringency and bitterness taste both in summer tea samples and autumn tea samples. There was no significance between summer tea samples and autumn tea samples in taste quality. Theanine, aspartic acid, glutamic acid and glutamine showed higher content in spring tea samples than in autumn tea samples than in summer tea samples; catehins, theasinesins, quercetin-O-glycosides and apigenin-C-glycosides showed higher content in summer tea samples and autumn tea samples than in spring tea samples. 3. There was significant difference between green tea produced by different fixation methods both in the taste quality including astringency, bitterness and umami, and composition of chemical components and content. Result of equivalent-quantification evaluation of green tea taste showed that bitterness of green tea samples produced by rotary continuous fixation was stronger than green tea samples produced by steam fixation and microwave fixation; astringency of green tea samples produced by steam fixation was stronger than green tea samples produced by rotary continuous fixation than tea samples produced by steam fixation. There was no significant difference in umami taste among tea samples produced by those three fixation methods. Bitter substances(eg.caffeine, coumaric acid and kaempferol)in green tea samples produced by microwave fixation showed lower content than green tea samples produced by rotary continuous fixation and steam fixation; astringent substances(eg. catechins, theasinesins and procyanidins) in green tea samples produced by steam fixation showed higher content than tea samples produced by rotary continuous fixation and microwave fixation; these three fixation methods showed no significant influence on the umami substances of green tea.