Optimization of brewing conditions for Tieguanyin oolong tea by quadratic orthogonal regression design

Tieguanyin is one of the most consumed oolong teas because of its distinctive flavor. The brewing process is crucial for the flavor performance of traditional teas, thus the effects of brewing conditions, including water/tea ratio (R), brewing temperature (T), and time (S) on the sensory traits, chemical composition, and antioxidant activity of Tieguanyin tea infusion were investigated using quadratic orthogonal regression design. Results showed that R affected all the quality variables most, its reduction could lead to the promotion of tea infusion concentration, antioxidant activity, and taste intensity, which was favored by the tea consumers drinking tea almost daily (DTD) but unacceptable for those drinking tea hardly (DTH). Based on the optimization of brewing conditions in response surface methodology (RSM), we recommended several brewing schemes for diverse consume goals: R = 34 mL/g, T = 80 °C, S = 80 s for DTH; R = 39 mL/g, T = 100 °C, S = 127 s for DTO (the consumers drinking tea occasionally); R = 20 mL/g, T = 100 °C, S = 100 s for DTD; R = 26 mL/g, T = 100 °C and S = 127 s for the common consumers seeking for flavor and health benefits. These results would be helpful for tea consumers with multiple demands.