| Wuyi Rougui Tea is famous for its spicy and long-lasting aroma,strong and full flavor,and it is one of the representatives of high-quality oolong tea in China.As the Wuyi Rock tea market continues to heat up,tea products of different grades,different baking degrees,and different areas appear on the market,and the traditional Wuyi Rock tea quality judgment mainly relies on sensory evaluation,requiring rich experience,personal factors of the reviewer greater impact.This has caused great difficulties for consumers to determine the quality of tea,which has seriously affected the interests of consumers and the healthy development of the rock tea market.In this experiment,the Wuyi Rougui tea collected in autumn 2017 was used as the research material.Based on the metabolomics method,the differences in aroma,taste characteristics and physical characteristics of the finished tea of Wuyi Rougui with different quality styles were systematically studied.It provides a data basis for objectively and scientifically evaluating the quality of Wuyi Rougui Tea,and provides a theoretical basis for improving the processing technology of Wuyi Rougui Tea and consuming different style products in the market.The research results are as follows:1.Differences in the quality of Wuyi Rougui tea at different baking levelsBy sensory evaluation,we screened the finished tea samples of Wuyi Rougui with different baking degrees that meet the conditions,and studied the physical characteristics,aroma and taste metabolites,revealing the quality differences of Wuyi Rougui Tea with medium and light roasting degrees.The results show that the a value of Wuyi Rougui Tea Soup with high-baking degree is significantly higher than that of low-baking degree tea,and the L value,b value,b/a value,Cab value,Hab value and Sab value are significantly lower than that of low-baking degree tea soup.Low-baking degree tea soup is brighter and more colorful than high-baking degree tea soup.Quantitative detection results of targeted metabolites showed that the content of total catechins and amino acids in Wuyi Rougui tea with high-baking degree was lower than that of low-baking degree tea.Among them,the contents of EGCG3''Me,EGCG,EGC and EC were significantly lower in high-baking degree tea than in low-baking degree tea.And the content of C,GC and GCG is significantly higher than that of low-baking degree tea.The content of each amino acid component of high-baking degree tea is significantly lower than that of low-baking degree tea.Among them,the theanine content of high-baking degree tea and low-baking degree tea is 0.48 and 1.97 mg/g,respectively,which is the highest content of amino acid,followed by Glu.Non-targeted metabolomics analysis of Wuyi Rougui tea which was baked in high and low level was conducted by using UPLC-QTOF MS.Principal component analysis shows that the two can be clearly separated in the direction of the first principal component.Amino acids,phenolic acids,flavanols,flavonols,esters,polycyclic aromatics and terpenoid glycosides are the main differences,of which flavanols and flavonols account for a relatively large amount.In addition,the relative contents of Theanine isomer1,3,4,3'-Tri-O-methylellagic acid,3-O-p-Coumaroylquinic acid,Linalool primeveroside isomer 1 and Epigallocatechin in high-baking degree tea are significantly lower than that of low-baking degree tea.The aroma compounds of Wuyi Rougui tea was identificated by GC-TOF MS.The results showed that the relative contents of aroma components such as furfural,pyrrole,Isophytol and Methyl salicylate in Wuyi Rougui Tea with high-baking degree were higher than that of low-baking degree tea.While Indole,?-Farnesene and Hotrienol,some ketone aroma components are lower than low-baking degree tea.The samples were tested after being stored for half a year.Common taste differences before and after storage included Theanine isomer 1,3-O-p-Coumaroylquinic acid,Gallocatechin and Linalool primeveroside isomer 1.The newly added differential metabolites after storage are Gallic acid,Kaempferol and Quercetin.After storage,the aroma substan-ces of alkanes,alcohols,aldehydes,esters,terpenes and pyrrole increased compared with before storage.Pyridines,pyrazines and nitriles are new types of aroma differences after storage.Common aroma difference substances before and after storage include 1-Octadecyne,Isophytol,Acetophenone,Methyl salicylate,?-Farnesene,Indole,and Furfurals.2.Differences in quality of Wuyi Rougui tea at different gradesAlthough the physical property parameters of different grades of Wuyi Rougui Tea Soup are different,the difference is not significant.High-grade tea soup has a yellowish color and high color purity.Lowgrade tea soup is relatively reddish.The total amino acid content of high-grade Wuyi Rougui tea is higher than that of low-grade tea,while the total catechin content is lower than that of low-grade tea.Among them,there are significant differences in C and Ala content,other components are not significant.The aroma and taste substances were analyzed by non-targeted metabolomic analysis.The relative contents of high-grade tea Theaflavins,Flavonol glycosides and other taste-different compounds were significantly higher than that of low-grade tea.The relative content of high-grade tea ?-Farnesene and Indole is higher than that of low-grade tea.However,2,4-Heptadienal,(E,E)-,Benzene,1,3-dimethyl-,furans,olefins and most ketones aroma compounds are lower than low-grade teas.The only taste difference between high and low grade tea after stora-ge is Kaempferol.After storage,2-Methyl-1-nonene-3-yne,Phenol,2-methoxy-4-(1-propenyl)-,(Z)-and other alkanes,phenols and alcohols are newly added differential aroma compounds after storage.3.Differences in quality of Wuyi Rougui tea at different areasAnalysis of physical characteristics of Wuyi Rougui tea in different areas shows that the a value of Waishan tea is significantly higher than that of Zhengyan tea.The color of Zhengyan tea soup is bright and yellowish,with high saturation.The contents of total catechins and total amino acids of Zhengyan tea are higher than those of Waishan tea.The content of EGCG,EC,EGC and caffeine in Zhengyan tea is significantly higher than that of Waishan tea,while the content of GCG and EGCG "Me is significantly lower than that of Waishan tea.Except for Arg,the content of other amino acid components of Zhengyan tea is significantly higher than that of Waishan tea.UPLC-QTOF MS for non-targeted analysis of Wuyi Rougui tea taste metabolites,Theanine isomer 1,3-p-Coumaroyl-1,5-quinolactone,3,3'-Di-O-galloylprocyanidin B5,Coumarin,3-O-p-Coumaroylquinic acid,Gallocatechin,Myricetin,Linalool primeveroside isomer 1?2,Theaflavin,etc.are the different substances of Wuyi Rougui tea in different areas.The different aroma substances of Zhengyan and Waishan Wuyi Rougui tea include esters,benzenes,furans,pyrroles,alkanes,olefins,terpenes,aldehydes and ketones.After storage,the amount of amino acid substances in Wuyi Rougui tea taste differences in different areas increased,and the amount of flavanols and phenolic acid differences decreased after storage.Common taste differences between Wuyi Rougui tea in different areas before and after storage include Theanine isomer 1,3-O-p-Coumaroyl-quinic acid,Gallocatechin,Linalool primeveroside isomer 1,2 and theaflavins.After storage,ketones,esters and alcohols become the main aroma difference substances.2,4-Heptadienal,(E,E)-,3,5-Octadien-2-one,(E,E)-,Geraniol,Acetophenone,etc.are common aroma differences before and after storage of Wuyi Rougui tea in different areas.To sum up,the color parameters,amino acid and catechin components of Wuyi Rougui Tea Tea Soup differ in different baking degrees and different areas,but the differences between different grades of tea are not obvious.The content of caffeine can only be used as one of the discriminating parameters of Wuyi Rougui tea in different areas.The rutin content was not significantly different in Wuyi Rougui tea of all quality styles.Compounds with different tastes are mainly concentrated in amino acids,phenolic acids,flavanols,terpenoid glycosides and theaflavins.Compounds with different aromas are mainly concentrated in ketones,aldehydes,indoles,terpenes,olefins and naphthalenes.It is precisely because of the difference in these metabolites that the different baking degrees,grades and areas of Wuyi Rougui tea have their unique quality characteristics.Exploring its characteristic meta-bolites can provide a theoretical basis for achieving scientific objective,intelligent,and standardized discrimination in the future. |
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