Flow Injection Analysis of (-)-Epigallocatechin Gallate in Green Tea Infusions with an Immobilized Tannase Reactor.

Abstract

A flow injection method to determine the concentrations of (-)-epigallocatechin gallate (EGCG) in tea infusions was developed. A bioreactor, packed with immobilized tannase, was connected to a pH-ISFET (Ion Sensitive Field Effect Transistor) electrode. The pH decrease, due to the gallic acid produced from EGCG by the enzyme reaction, was monitored by the electrode. The response of this system was linear between 50 mg/ I and 1,000 mg/ I of EGCG. The sample could be injected every 3 min. The concentrations of EGCG in green tea infusions obtained by this FIA method showed a fairly high correlation with those by HPLC.