Studies On Rock Taste Composition And Corresponding Instrumental Assessment Of Wuyi Rock Tea

Wuyi Rock Tea is a kind of Olong tea in Northern Fujian province,China.Meanwhile,it is also one of Chinese top 10 teas,which has been well known in China for its unique flavor character.It has been the earliest product of geographical indication in Fujian since 2002.The scale of the industry has grown in a high speed for many years,and it has became a pillar industry in Northern Fujian province.The rank of Wuyi Rock Tea is classified by its Charecter of "Rock Taste",which though to be a key identical features from the other tea.It is believed traditionally that the first-class flavor of Wuyi Rock Tea should be charactered with fresh,fragrant,sweet and active.However the unique character of "Rock Taste" is hard to seized.Therefore the problems mentioned above creating problems for sensory evaluation and quality control of Wuyi Rock Tea.The database of multiple fingerprint of Wuyi Rock Tea was established to analyse the formulation of“Rock Taste,by data mining method.Several modern technologies including E-nose,E-tongue and Near infrared spectrummetre were applied in the study to establish a evaluation system of Wuyi Rock Tea.All these results will be helpful in clarty the mechenism of "Rock Taste" composition,and also provide some practical methods in quality control and sensory evaluation of Wuyi Rock Tea.The main results were listed as follows:(1)The Establishment of Database with Multiple FingerprintsSensory evaluation was applied to classfy the rank of corresponding samples.Physiochemical analysis,chromatography,spectroscopy,mass spectrometry,E-nose and E-tongue were applied to acquire fingerprints of Wuyi Rock Tea.6 physiochemical analysis results,18 kinds of amino acid quantification results,11 kinds of main selected tea polyphenols quantification results,GC-MS fingerprints of fragance,20 kinds of mineal elements,NIR frigerprints of samples,E-nose dates of fragance and E-tongue dates of liquor were all included in the datebases.(2)Compareation of the Biochemical Components in Different Cultivated VarietiesThe results showed that,for physicochemical properties,"Wuyi Shuixian" had higher theaflavins.For the selected polyphenols,epigallocatechin,epigallocatechin gallate,gallocatechin gallate were found to be lower in"Wuyi Rougui",while chlorogenic acid and quercetine-glycosides were lower in "Wuyi Shuixian".Meanwhile there were neighter myricetine nor quercetine to be detected in all samples.For free amino acid,phenyl-alanine,glycin,leucine,valine and histidine were higher in"Wuyi Rougui" Besides,the other biochemical components tested in the study(including tea polyphenols,total free amino acid,caffeine,crude fiber,total ash,thearubigins,gallic acid,catechin,L-epicatechin,epicatechin gallate,myricetin-glycoside,alanine,theanine,methionine,proline,glatamic acid,eystine,arginine,lysine,tyrosine,serine,threonine,aspartic acid,isoleucine),were not found to be significant different(P<0.05).In particular,the study found that the distinctive mellow taste of "Wuyi Shuixian" is relatived with high level of catechin content,while the sharp taste of"Wuyi Rougui" is contributed by high level of astringencied amino acids.That were different form the prime opinion which though the astringency taste was mainly attributed by catechins.For some test specifications,such as water-soluble protein,tea polysaccharide and pectin,are not including in the research,further experiments should be carried out to confirm their effects in the formation of tastes.For the study of discriminal model of cultivarity varities which base on HPLC-DAD figerprint database,the results showed that they could be discriminated well by primary compounds analysis,K-mean and two-step cluster methods.The results also indicated the key point of taste characters was mainly contributed by different compositions of taste compounds.The Fragrance Analysised by GC-MS:The analysis results of fragrance by GC-MS indicated that there were 6 same compounds including Phenylacetaldehyde,(Z)-3,7-dimethyl-1,3,6-eighteen alkyl triene,3,7-dimethyl-1,5,7-symplectic triene-3-alcohol,benzyl cyanide,caproic acid allyl ester,Hexyl Hexanoate and?-famesene were found in these two cultivated varieties.Meanwhile there were no compound to be found as distinction for corresponding cultivated varieties.(3)Mechanism of "Rock Taste,Composition of Different Taste Level of Two Cultivate Varieties of Wuyi Rock TeaKendall correlation analysis and Mann-Whitney U analysis were applied in the study.The results showed that there were significant correlation between total amino acids,theanine,serine,theabrownins and gallic acid to taste rank of "Wuyi Shuixian".Specifically,total amino acid content,especially for the content of theanine and serine,had positive effect to its taste rank.While there were negative effect between the content of theabrownins as well as gallic acid and its taste rank.It was noteworthy that epigallocatechin gallate(EGCG)and epigallocatechin(EGC)may have positive efforts for the improvement of "Wuyi Shuixian" Tea taste.For "Wuyi Rougui",glycine had positive effect to its taste rank.While tea polyphenols,caffeine and catechine had positive effect to its taste rank.Comparely speaking,there were more interacted contribution for its taste formulation in "Wuyi Rougui" than in "Wuyi Shuixian".(4)Quality Difference in Wuyi Rock Tea Originated from Famous Producing Areas and Normal Producing AreasThe results of comparetion showed that there were significant difference in Cr,Ni,Ba,K and Cd originated from these two areas for "Wuyi Shuixian" Tea.While there were significant differences among TFs,TBs,GCG,arginine and Na originated from these two areas for "Wuyi Rougui" Tea.Besides these compounds mentioned above,there were no significant difference among the other compounds originated form these two areas.The results also indicated that the originated areas can be discriminated by the comtents of Mn and K with corresponding discriminant algorithms.Comparely speaking,all these algorithms methods including four kinds of decetion trees(CHAID,QUEST,C5.0 and C&R),discriminant algorithm,artificial neural network and logistic algorthm can make the right decision with which accuracy above 70%.Further more,the most confident method was C&R with which accuracy above 92.75%.All the results also indicated that the figerprints which established by minal elements were more suitable for discrimination of originated place compared with chromatography fingerprints.(5)The Application on Sensory Evaluation with E-tongue and E-nose MethodsThe discriminat models of cultivated varities were established with E-tongue and E-nose methods successfully.The characters of stabilization and abundance were better in E-tongue than in E-nose which indicated that the E-tongue was more suitable for the application of sensory evaluation of Wuyi Rock Tea.The models which could classified its rank of sensory automatic were established successfully.The results of their significant test showed that the models were meanful.(6)Simultaneous Determination of Caffeine and Some Selected Polyphenols in Wuyi Rock Tea by High Performance Liquid ChromatographyDue to very many kinds of flavonoid glycosides in tea and lack of commercial standard of flavonoid glycosides,it is critical for developing a rapid and cheap methed for determing flavonoid glycosides of tea.Contents of myricetin glycosides and quercetin glycosides in Wuyi Rock tea were detected by detecting contents of corresponding myricetin and quercetin.Optimizing hydrolysis conditions for hydrolyzing flavonoid glycosides to their corresponding flavonols including quercetin and myricetin tea was a key technology for detecting contents of corresponding myricetin and quercetin.The results showed that hydrolyzing at 2 mol/L HCl solution and at 90? for 1 h was an optimizing condition for hydrolyzing flavonoid glycosides to myricetin and quercetin in Wuyi Rock tea.Caffeine and seven kinds of polyphenols(GA,EGC,C,EGCG,L-E,ECG and CGA)simultaneously determinated using a simple and fast reverse-phase high-performance liquid chromatography procedure coupled with photo diode array detector.(7)Qunatification of Some Selected Quality Compounds in Wuyi Rock Tea with NIR MethodsNear infrared reflectance spectroscopy(NIRS)is a kind of online inspection technology,which has been widely used in many areas for rapid qualitative and quantitative analysis.The purpose of this research is to apply NIRS technology to the routine online inspection processing of Wuyi Rock tea.The quantification models of some selected quality compounds including moisture,caffeine,tea ployphenols and crude fiber were established.Four chemical components such as moisture,caffeine,tea polyphenols and crude fiber were detected in laboratory with corresponding Chinese National Standard methods.TQ Analyst 8.5 spectrum metrology analysis software was applied in modeling processing.Several mathematical pretreatment methods and model methods were analyzed and compared.The results showed that moisture can be predicted by PCR model,assisted with First derivative and Savitzky-Golay smoothing pretreatment.The correlation coefficient and mean square error of determination in prediction model of moisture was 0.9815 and 0.0812%,respectively.The tea polyphenols can be predicted by PCR model,needless with derivative and smoothing pretreatment.The correlation coefficient and mean square error of determination in prediction model of tea polyphenols was 0.7427 and 0.748%,respectively.The caffeine can be predicted by PCR model,needless with derivative but assisted with Savitzky-Golay smoothing pretreatment.The correlation coefficient and mean square error of determination in prediction model of caffeinewas 0.8601 and 1.39 g/kg,respectively.The crude fiber can be predicted by PCR model,needless with derivative but assisted with Savitzky-Golay smoothing pretreatment.The correlation coefficient and mean square error of determination in prediction model of tea polyphenols was 0.8840 and 0.580%,respectively.Comparing with requirement of deviation for corresponding Chinese National Standards methods,the moisture model was better than its error requirement.The caffeine model,tea polyphenols model and crude fiber were all not as good as the error requirement.But they were good enough for the requirement of routine online inspection.