Availability of Reactive Oxygen Species Scavengers in the Conventional Tea and Coffee

The antioxidant capacities of black coffee and two different teas such as green tea and black tea were determined using the trolox equivalent antioxidant capacity (TEAC) method. The green tea showed approximately 40% higher antioxidant capacity compared with the other two beverages, and the obtained TEAC values for green tea, black tea, and coffee were 8.79, 6.20, and 6.30 μmol trolox/mL of the sample, respectively. When the teas were prepared with cold water (20 °C ± 1°C), the total available antioxidant capacity reduced significantly, with TEAC values of green tea and black tea of 1.34 and 1.42 μmol trolox/mL of the sample, respectively. Per individual serve, hot teas and coffee could provide approximately four- to sixfold more antioxidants compared with teas prepared with cold water. With the kinetics experimental data, the 2,2 ′-aziono-bis(3-ethylbenzthiazoline-6suphonic acid) radical scavenging rate by green tea with cold water can be expressed as a pseudo-first-order reaction. The obtained pseudo-first-order reaction rate constant was 0.147 min �1 , indicating that the reduction rate of undesirable reactive