FOOD SCIENCE ›› 2010, Vol. 31 ›› Issue (22): 343-348.doi: 10.7506/spkx1002-6630-201022075

• Analysis & Detection • Previous Articles     Next Articles

Determination of Polyphenols and Alkaloids in Tea and Cluster-Linear Discrimination Analysis

XIAO Jun-song1,2,YUAN Ying-hao1,ZHANG Ai-xue1,CAO Yan-ping1,2,*   

  1. 1. School of Chemical and Environmental Engineering, Beijing Technology and Business University, Beijing 100048, China;
    2. Beijing Higher Institution Engineering Research Center of Food Additives and Ingredients, Beijing 100048, China
  • Received:2010-07-08 Online:2010-11-25 Published:2010-12-29
  • Contact: CAO Yan-ping1


Objective: To establish a HPLC method for the determination of (+)-catechin, (-)-epicatechin (EC), (-)-epicatechin gallate (ECG), (-)-epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCG), gallic acid (GA), caffeine (CAF) and theobromine (THEO) in green, oolong and black tea samples, and to develop a discrimination method for green, oolong and black tea by cluster analysis and linear discrimination analysis on the basis of determined chemical components. Methods: Tea samples were extracted by 70% aqueous methanol. Totally 200 mg of grinded tea samples was extracted with 5 mL of 70% aqueous methanol for 10 min in 70 ℃water bath. The extract was centrifuged at 3500 r/min for 10 min, and the supernatant was collected. Then the precipitate was extracted with 5 mL of 70% methanol under the same conditions. The supernatants were combined in a volumetric flask and diluted to 10 mL. A total of 2 mL of such solution was diluted by 5 times with stabilizing solution, filtrated with 0.45 μm membrane, and then used for HPLC analysis. Eight compounds were separated by a C18 column using a mobile phase containing methanol-2% aqueous acetic acid at a ratio of 25:75 (V/V) in an isocratic elution at 30 ℃, and detected using a photodiode array detector at 278 nm with the reference wavelength at 210 nm. The cluster and linear discrimination analyses were performed using SPSS 14.0 software. Results: Eight compounds in all tea samples were well separated under the proposed conditions. The recovery rates of spiked samples were in the range of 87%-112.8%. The contents of 8 compounds determined by an external standard method were used to conduct cluster analysis and linear discrimination analysis. The good differentiation of green, oolong and black tea samples were achieved. Conclusion: This established method is feasible to discriminate green, oolong and black tea.

Key words: tea polyphenol, caffeine, tea, high performance liquid chromatography (HPLC), cluster analysis, linear discrimination analysis

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