Microwave-assisted extraction of tea phenols: a phenomenological study

In this paper, aqueous microwave-assisted extraction (MAE) of total phenols from black tea powder was investigated in an ordinary household microwave oven. Influence of microwave power (450–600–900 W) and irradiation duration (30–210 s) on total phenols concentration and antioxidant activity was investi gated. MAE allowed higher recoveries compared to conventional brewing technique, without altering the antioxidant potential of the extracts. Experimental data indicated to follow first-order kinetics. Total phe nols diffusion at different water to tea ratios was studied, and the results varied depending on how the ratio was modified (that is at either constant tea mass or water volume), due to the characteristics of microwave heating. In trials at constant solvent volume, infusion temperature resulted constant and experimental data could be successfully predicted by a simplified mass transfer model. MAE process can then be predicted and controlled for industrial application, but attention must be paid to both sample size and solvent to solid ratio.