Studies On Similarities And Differences Of Aroma And Taste Of Teas From Three Longjing Tea Producing Regions

Twelve tea samples were choosen from Xihu producing region, Qiantangproducing region, Yuezhou producing region, oblate-tea Jingtinglvxue from southAnhui province was used as CK, all thirteen tea samples were made from tea cultivarLongjing43, picked at the same time and processed under the same method, toinquire into the differences of aroma and taste in Longjing tea from differentproducing regions. The methodology of sensory evaluation of tea was adopted toevaluate the aroma and taste score of Longjing teas from different producing regions.The tea aroma was extracted by SDE (Simultaneous Distillation and Extraction)method, then qualitatively and quantitatively analysed by GC-MS (GasChromatography and Mass Spectrometer), as well as referring to the retention timeand the content of the injected authentic commercial samples. Nine compounds wereselected as characteristic aroma component of Longjing tea. Using the ninecomponents as variables and thirteen tea samples as entities, a cluster analysis wasexecuted. The electronic tongue was used to obtain the general taste information ofLongjing teas, and pattern recognition method were used to analyse the tea samplesand then compared the results with their real producing regions. HPLC (HighPerformance Liquid Chromatography) was adopt to analyse the two major tastecomponents (catechins and amino acids), and compared the differences with theelectronic tongue result. The specific results were as follows:(1) Sensory evaluation results showed that the order of aroma and taste scorefrom high to low was Xihu producing region, Yuezhou producing region, oblate-tea,and Qiantang producing region respectively. The score of tea samples from Yuezhouregion was similar with teas from Xihu producing region.(2) GC-MS results showed that aroma composition in three tea producingregions and oblate-tea Jingtinglvxue had high similarity. Individual and content ofaroma components in Xihu producing area were much higher than other teaproducing regions.(3) The rule for selecting characteristic aroma components was established, and nine components such as linalool, cis-3-hexenyl caproate, β-ionone, nerolidol,benzaldehyde, nonanal, geraniol, cedrol, trans-furanoid linalool oxide were choosedas characteristic aroma components. Cluster analysis divided the thirteen tea samplesinto two groups. The six tea samples from Xihu producing region got together toform a group, which still contained one tea from Qiantang producing region and onetea sample from Yuezhou producing region. The other five tea samples clusteredtogether to form another group. Although Shuangpu Town belonged to Xihuproducing region, its aroma was different from other six teas from Xihu producingregion. Oblate tea-Jintinglvxue could not be clustered into Xihu producing regiongroup.(4) The electronic tongue results showed that thirteen was divided to threegroups. Five tea samples from Xihu producing region were clustered into the samegroup. Four tea samples from Qiantang producing region and Yuezhou producingregion were clustered into one group，two tea samples from the outer area of Xihuproducing region were clustered into this group as well. Tea samples from Tonglucounty of Qiantang producing region and oblate-tea Jingtinglvxue were clusteredinto the third group, and this group kept the greatest distance with other two groups.The classification result of electronic tongue was basically matched with its actualgeographical producing regions.(5) The gradient elution method of HPLC could separate six catechins and17free amino acids. The results of HPLC analysis showed that EGCG was the mostabundant in six catechins with an average amount of103.70mg/g, almost halfcontent of the total six catechins. The content of seventeen free amino acids in drytea ranged from1.405%to2.324%, with an average of1.930%. Theanine had themost abundant content in seventeen amino acids, and the average was43.85%. Totalcatechins in tea samples from Xihu producing region was the highest in three groups,total content of free amino acids and the ratio of ployphenols to amino acids were atthe middle level in three groups.(6) It was thought that the most individual number and the most abundantcontent of aromatic components, and the balance of two main taste conponentscaused the great quality of Xihulongjing tea. The difference of Longjing teas fromseveral producing regions could be disclosed based on the appropriate parameters and multivariate analysis.