Effects of brewing conditions on the antioxidant capacity of twenty-four commercial green tea varieties

Abstract

A novel paper-based Nanoceria Reducing Antioxidant Capacity (NanoCerac) assay for antioxidant detection (Sharpe, Frasco, Andreescu, & Andreescu, 2012), has been adapted for the first time as a high-throughput method, in order to measure the effect of brewing conditions and re-infusion on the antioxidant capacity of twenty-four commercial green teas. The oxygen radical absorbance capacity (ORAC) assay, frequently applied to complex foods and beverages, was used as a comparator measure of antioxidant capacity. A novel measure of sustained antioxidant capacity, the total inherent antioxidant capacity (TI-NanoCerac and TI-ORAC) was measured by infusing each tea six times. Effects of brewing conditions (temperature, brew time, etc.) were assessed using one popular tea as a standard. Both NanoCerac and ORAC assays correlated moderately (R2 0.80 ± 0.19). The average first-brew NanoCerac, TI-NanoCerac, first-brew ORAC and TI-ORAC were: 0.73 ± 0.1 GAE/g tea ; 2.4 ± 0.70 mmol GAE/g tea; 1.0 ± 0.3 mmol TE/g tea and 2.1 ± 0.71 mmol TE/g tea respectively. Brewing conditions including water temperature and infusion time significantly affected antioxidant capacity. The high-throughput adaptation of the original NanoCerac assay tested here offered advantages over ORAC, including portability and rapid analysis.

Evaluation of antioxidant capacity of Aidia borneensis leaf infusion, an endemic plant in Brunei Darussalam

“…Figure 3A shows that the total antioxidant capacity of A. borneensis leaves increases abruptly with brewing temperature (in the range of 10-100°C). A similar tendency has also been observed for C. sinensis black and green teas, where infusion with greater antioxidant capacity was obtained at longer brewing time and higher temperatures (Sharpe et al, 2016). This finding implies that more phytochemicals and polyphenol derivatives from the A. borneensis leaves are infused into the water due most probably to the existences of more openings and interstices on the leaves, increasing the diffusion rate at higher brewing temperature.…”

The total antioxidant capacity and fluorescence imaging of selected plant leaves commonly consumed in Brunei Darussalam

“…We should note that the total antioxidant capacity of the infusions of the C. asiatica, A. borneensis, and A. occidentale leaves is abruptly increased either with higher brewing temperature or longer brewing time [23]. Similar tendency has also been observed for C. sinensis black and green teas [24]. However, in our previous study, we have demonstrated that more than 90% of the total antioxidant capacity was achieved at brewing temperature of 60°C, for the first 3 min infusion time [23].…”

Comparative Study of the Antioxidant Capacity in Green Tea by Extraction at Different Temperatures of Four Brands Sold in Colombia

“…An increase in TPC resulted in the increase of DPPH radical scavenging in tea infusions, a study suggested higher water temperature and shorter steeping time as the best combination for improving the herbal teas beneficial health effects in terms of antioxidant properties (7). The antioxidant activity of green tea Liptón ® obtained in this study was compared with the study of another reported author who determined the activity of 24 commercial samples, where the brand Lipton ® reported 1000 μmol trolox eq/g per sample (23), similar to the results obtained by hot extraction (95.25 ± 0.24 mg trolox eq/g per sample). Catechin polyphenols are believed to be the most important active component in green tea.…”