The changes of catechins during the fermentation of green tea.

The dynamics of tea catechins and organic acids in fermented fluid and yeast cells were studied. The concentration of eight kinds of catechins solution decreased by from 29.6% to 47.6%, respectively, some catechins were absorbed and accumulated by yeast cells, but the amount in the cells was very low during the fermentation process. The investigation of catechins resolved in four citrate buffers with a pH range of 2.6-5.6 for 18 h showed that most catechins were stable in buffer solutions of pH 4.6 and 5.6, and significant losses took place in solutions of pH 2.6 and 3.6. However, most catechins were released and recovered by adjusting the pH value to 5.6, which suggested that catechins in extremely acidic buffer solutions might reversibly combine each other or with other compounds.