The Relationship Between Oolong Tea Chemical Components And Quality & Separation Of Its Polyphenol

Oolong tea,is manufactured predominantly in Fujian and Guangdong provinces of China as well as in Taiwan.Properties of leaf and infusion colors,chemical components,and volatile flavor compounds of 30 Oolong tea samples collected directly from tea farmers of core production area were analyzed with the aim to explore their relationship with the perceived quality assessed by sensory evaluation. Pearman's linear correlation analysis showed that concentration of total free amino acid,total chlorophyll,chlorophyll-a,chlorophyll-b,infusion light-black indicator△L,red-green indicator△a,yellow-blue indicator△b,total colour difference indicator△E were significantly correlated with total quality score,respectively.The volatile composition and their quantities varied widely among Oolong tea samples. Linalool,linalool oxides,(E)-geraniol,hexanal,Benzeneacetaldehyde,Benzyl nitrile, (Z)-2-penten-1-ol and cis-jasmone were prevailing volatile compounds detected in all samples.Principal component analysis(PCA) screened ten principal components explaining 90.46%variance with the concentrations of EGCG,△b and 2-penten-1-ol as the first three major components.Regression analysis upon the ten principal components formulated a prediction model on the TQS with 72.10%probability. Cluster analysis based on principal components further showed that Oolong green teas might be partially classified into four different groups according to their origins.High-speed countercurrent chromatography(HSCCC) has been applied for the separation of oolong tea polyphenols.The HSCCC run was carried out with a two-phase solvent system composed of hexane-ethyl acetate-methanol-water-acetic acid(1:5:1:5:0.25,v/v) by eluting the lower aqueous phase at 2 ml/min at 700 rpm. The results indicated that catechins including epigallocatechin gallate,gallocatechin gallate,epicatechin gallate and epigallocatechin were isolated from the aqueous extract of oolong tea and green tea.The potential of polyamide as sorbent in the separation of nine compounds in oolong tea:(±)-catechin(DL-C),(-)-epicatechin(EC),(-)-epigallocatechin(EGC), (-)-epicatechin gallate(ECg),(-)-epigallocatechin gallate(EGCg),TF1,TF2A,TF2B and TF3 was studied.The use of chloroform-methanol(2:3,v/v,two fold development) as developing solvent resulted in the separation of TF1,TF2A,TF2B and TF3 from all the other compounds.Meanwhile,EGCg,ECg and EGC were separated,while EC and DL-C were not separated from each other.The best choice for developing solvent is given for each of the studied compounds.The best separation of the five main catechins(EC,DL-C,EGC,ECg,EGCg) was achieved using n-buthanol-acetone-acetic acid(5:5:3,v/v/v).In addition,the separation of flavonols(myricetin,quercetin,kaempferol and rutin) and phenolic acids(gallic acid, chlorogenic acid and caffeic acid) was achieved using chloroform:methanol(2:3,v/v, two fold development).The applicability of the developed method was checked for screening of the extracts of oolong tea.