Effect of brewing temperature and duration on green tea catechin solubilization: Basis for production of EGC and EGCG-enriched fractions

In an industrial context of producing catechin-enriched fractions by electromigration, a new technology demonstrated to be effective for concentration of the two main catechins (EGC and EGCG) of green tea, the recovery yield from tea leaves during brewing would be the most important parameter of the whole process rentability. However, the majority of the kinetic studies were carried-out on black tea, a fermented tea. Consequently, the objective of this study was to investigate the effects of temperature (50, 60, 70, 80 and 90 °C) and brewing duration (0, 5, 10, 20, 40 and 80 min) on the catechin solubilization from green tea, a non-fermented tea. The use of mathematical models revealed that there was a variable interdependence between the brewing duration and the brewing temperature on catechin and caffeine concentrations. It was possible to divide catechins in two groups, the time dependent compounds (EGC and EC) and the time/temperature dependent compounds (C, EGCG, GCG and ECG). Furthermore, the 3D models calculated to represent the evolution of the catechins and caffeine concentrations allowed to determine the best combination of time and temperature for their extraction: 50 °C during 20–40 min for time-dependent compounds, 90 °C during 80 min for the time/temperature-dependent compounds, and 70–80 °C during 20–40 min for caffeine. Furthermore, this research pointed out a very simple two-step procedure to fractionate the EGC and EGCG by modifying brewing temperature and time parameters.