The effect of ascorbic acid, citric acid and low pH on the extraction of green tea: How to get most out of it
Author: Benno F. Zimmermann and Maike Gleichenhagen
Green tea seems to have a positive impact on health due to the therein-found flavanols. The amounts of these substances depend on tea preparation. In this paper, the influence of steeping time (3–7 min) and temperature (70–100 °C) on the content of the main flavanols in green tea (epicatechin EC, epicatechin gallate ECg, epigallocatechin EGC, and epigallocatechin gallate EGCg) is presented. Furthermore, additives (phosphate buffers, ascorbic acid in different amounts, and citric acid) are used to investigate the influence of pH, antioxidative, and chelating agents, simulating the addition of lemon juice or pure vitamin C. The concentrations of flavanols in tea without additives are highest after 7 min of steeping at a constant 100 °C; the respective lowest and highest concentrations of the flavanols differ widely: 2.1-, 2.2-, 3.1-, and 3.6-fold for EC, EGC, EGCg, and ECg, respectively. The additives increase the flavanol concentrations up to 20%. pH emerges as the decisive factor for increasing concentrations, rather than the chemistry of the used additive.