| Mingke 1,Jinmudan and Zimeigui are oolong tea varieties,which all are next breeding generation of Tie guanyin and Huangdan.Currently,Mingke 1 and Jinmudan have been large scale cultivated in Fujian tea area.However,it is still a lack of systematic research for its unique flavor and quality characteristics of three varieties of congou black tea.In this research,by in-depth analysis the quality characteristics of congou black tea,the three varieties could be well distinguished.And this paper has laid the theoretical foundation of application and promotion for three varieties.At the same time,it has provided a feasibility for a variety of instrumental analysis techniques applied in the evaluation of tea quality.In this research,the main results obtained are as follows(1)Study on quality of infusion color.The infusion color of Mingke 1 congou black tea is orange-red with slightly brighter.The eigenvalue or the material contents in tea infusion are as follows:L*(an indicator of light and dark)is 20.09±0.94,a*(an indicator of red and green)is 9.02±1.25,b*(an indicator of yellow and blue)is 26.95±1.47,content of theaflavins is(0.60 ±0.14)%,content of thearubigins is(9.84±1.33)%and that of theabrownin is(6.33 ±0.95)%.The infusion color of Jinmudan congou black tea is between light orange-red and bright orange-red.The eigenvalue or the material contents in Jinmudan congou black tea infusion are as follows:L*is 18.57±1.11,a*is 12.37±1.56,b*is 24.09±1.12,content of theaflavins is(0.59±0.14)%,content of thearubigins is(8.75±1.38)%and content of theabrownin is(5.40±0.46)%,respectively.For Zimeigui congou black tea,the color of tea infusion is orange-yellow with slightly brighter and red brighter.And the eigenvalue or the material contents in tea infusion are as follows:L*is 20.93±3.20,a*is 8.19±4.53,b*is 23.26±4.66,theaflavin content is(0.55±0.15)%,thearubigins content is(8.23±2.05)%and theabrownin content is(7.07±1.03)%The discriminant functions based on the datas of infusion color for the three tea varieties are as follows:Mingke 1 congou black tea:Y1=-106.071-2.425X2+4.191X3-1.998X4-139.382X5+9.032X6+17.042X7 Jinmudan congou black tea:Y2=-72.946+2.755X2+1.264X3+8.245X4-94.684X5+5.672X6+12.811X7.Zimeigui congou black tea:Y3=-112.064+2.288X2+0.776X3+10.510X4-154.971X5+7.253X6+25.003X7The above-mentioned X2,X3,X4,X5,X6 and X7 represent a*,b*,b*/a*,theaflavins,thearubigins and theabrownins,respectively.The total percent of right interpretation for back substitution and cross validation are 100%and 94.1%,which indicates an effective discrimination for Mingke 1 and Jinmudan congou black tea,and the basic discrimination for Zimeigui congou black tea can be achieved(2)Study on aroma quality.The flowery flavour of Mingke 1,Jinmudan and Zimeigui congou black tea are obvious.61,69 and 53 kinds of aroma components and 95,118 and 79 kinds of aroma components were detected in dry samples and infusions of Mingke 1,Jinmudan and Zimeigui congou black tea,respectively,by using GC-MS analysis method.Among the components,the content of alcohols are the highest.The main fragrant substances of the three high aroma varieties of congou black tea are different.For Mingke 1 congou black tea,they are linalool,linalooloxide,methylsalicylate,hexanal,3-hexen-1-ol,(Z)-3-hexen-1-ol and so on.For Jinmudan congou black tea,they are linalool,linalooloxide,methy lsalicylate,phenylethyl alcohol,geraniol,hexanal,benzaldehyde,(Z)-3-Hexen-1-ol and so on.And for Zimeigui congou black tea,they are linalool,linalooloxide,methylsalicylate,hexanal,benzaldehyde,3-hexen-1-ol,(Z)-3-Hexen-1-ol and so on.Moreover,after brewing,the contents of some aroma components of green dour have decreased,such as 3-hexen-1-ol and(Z)-3-Hexen-1-ol.However,the contents of some aroma components with pleasant characteristics have increased,such as benzeneacetaldehyde and beta-myrcene.The discriminant functions based on E-nose detection results of tea aroma for the three varieties are as follows:Mingke 1 congou black tea:Y1=-78.070-288.562S1+180.140S4+172.359S8.Jinmudan congou black tea:Y2=-107.818-328.439S1+204.917S4+197.726S8.Zimeigui congou black tea:Y3=-56.195-234.642S1+153.759S4+137.490S8.The above-mentioned S1,S4 and S8 represent the different sensor response characteristic value of E-nose.The total percent of right interpretation for back substitution and cross validation are 91.1%and 88.9%respectively,which indicates an effective discrimination for the three varieties of congou black tea.(3)Study on taste quality.The taste of Mingke 1,Jinmudan and Zimeigui congou black tea are mellow and thick.The contents of material related to the taste in tea are as follows:as for Mingke 1 congou black tea,water extracts is(39.01±1.72)%,tea polyphenol is(17.42±1.52)%,total free amino acids is(5.19±0.59)%,caffeine is(4.72±0.54)%and soluble saccharide is(6.34±0.83)%;for Jinmudan congou black tea,water extracts is(38.14±1.78)%,tea polyphenol is(17.76±0.97)%,total free amino acids is(5.23±0.94)%,caffeine is(4.87±0.51)%and soluble saccharide is(6.54±0.94)%;in Zimeigui congou black tea,water extracts is(41.52±3.79)%,tea polyphenol is(16.17±2.13)%,total free amino acids is(6.46±1.68)%,caffeine is(5.23±0.43)%and soluble saccharide is(5.53±0.86)%.From the results of discriminant functions,the three varieties of congou black tea could be basicly distinguished by the major chemical components.Jinmudan congou black tea could be distinguished from Mingke 1 and Zimeigui congou black tea by catechins and amino acids,but it is hard for them to make a correct judgment of Zimeigui congou black tea.However,E-tongue detection showed a good judgement for the three high aroma varieties of congou black tea.The discriminant functions based on E-tongue are as follows:Mingke 1 congou black tea:Y1=-168.133+2325288.532X3-3483777.156X13+…+3414558.763X118-668125.193X120.Jinmudan congou black tea:Y2=-165.403+1678683.583X3-2932264.025X13+…+3716721.910X118-495093.231X120.Zimeigui congou black tea:Y3=-143.013+2069821.309X3-4021045.418X13+…+2656840.458X118-1 058705.159X120.The above-mentioned X3,X13…X118 and X120 respectively represent the electrode of platinum 100Hz d2p10V,platinum 100Hz maxp7V…silver 1Hz d1p1V and silver 1Hz d2p1V.The total percent of right interpretation for back substitution and cross validation are 99.4%and 97.6%,respectively.(4)Comparation of instrumental analysis and organoleptic evaluation.The GC-MS and E-nose combine with principal component analysis could well distinguish three kinds of congou black tea of Mingke 1,Jinmudan and Zimeigui from the pros and cons in aroma quality.However,the HPLC,automated amino acid analyzer and E-tongue are pool distinguish taste quality of this three kinds of congou black tea,which possiblly related with the small differences in quality of tea samples tested in this study. |
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