Investigation of processes in black tea manufacture through model fermentation (oxidation) experiments.

Flavanol depleted whole fresh green tea leaf powder, as reported in the literature, was used as matrix for a systematic study of the endogenous oxidative enzymatic conversion of selected flavanol combinations to theaflavins and thearubigins. The activity of the two crucial enzymes polyphenol oxidase (PPO) and peroxidase (POD) was controlled individually through addition of H2O2 and/or O2. Using the endogenous peroxidase only it was shown that (-)-epicatechin alone did not react with POD.