The Impact Of Processing Methods On Tea Chemical Composition Using Metabolomics Approaches

According to the different methods,tea is processed by the fresh leaves which can be classified into Green tea,Yellow tea,White tea,Oolong tea,Black tea and Dark tea.Because of the processing methods,the various types of tea have significant difference from color,flavor and shape which is truly influenced by the varieties and contents of teas' compounds.The majority compounds in tea can be labeled such as catechins,flavonoids and their glycosides,alkaloids,amino acids and phenolic acids.In the past studies of processing impacting on the tea chemical profiling,most of them were using the commercial goods which will lead to the material and processing methods lacking of consistency and normalization.Meanwhile,there was another shortcoming existing in the past studies that the analysis methods usually detected the single chemical component and the statistical methods were limited to univariate statistics.Both of them will result in that researching on the influence of processing on chemical profiling in tea may be not scientific and comprehensive.In the light of the weaknesses from the above,this study combines the teas which were processed by six typical methods using consistent starting fresh leaf and metabolomics ways to analysis the influences of six typical methods to chemical profiling.The main research contents and results are as follows:1 Metabonomics can distinguish the six kinds of processing method.The 2489 features were detect in chemical profiling;112 kinds of compounds were identified including Amino acids(13),Catechins(29),Flavonoids and their glycosides(30),Phenolic acids(28),Alkaloids(6),Chlorophyll(3)and others(3).The profiling of Dark tea is obviously different from others Meanwhile the profiling of Black tea is similar with White tea and the same phenomenon happened between the Green tea and Yellow tea.2 After the processing,the chemical profiling of green tea and yellow tea does not change significantly;compared with other teas,pheophorbide B etc.were sharply changed in oolong tea;catechins,eriodictyol,chlorogenic acid,salicylic acid and caffeic acid etc.were sharply changed in black tea;amino acid,GABA etc.were sharply changed in white tea;valine,betaine and theophylline etc were sharply changed in dark tea3 Compared with the two processing factors,Theanine,,Theophylline,Valine and others are the significantly different compounds influenced by post fermentation;Leucine,Epigallocatechin,?-aminobutyric acid,Eriodictyol and others are the remarkably different compounds influenced by enzymatic reaction.This research through metabolomics ways analyses the chemical profiling of teas processed by six typical methods using consistent starting fresh leaf.This study comprehensively evaluates the variety and content of chemical components influenced by six typical methods and reaches the compounds affected by the key processing steps.Simultaneously,the research also provides a new theoretical support to mine the characteristic compounds among the various tea varieties.