| The correlation of L-theanine and caffeine levels with the antioxidant activities of different tea extracts and changes in L-theanine and caffeine in white tea extracts supplemented with milk |
| Paper ID : 1206-IGA |
| Authors |
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Mina Allameh * Department of Bioresource Engineering, McGill University, 21111 Lakeshore Road, Ste-Anne-de-Bellevue, Québec, Canada |
| Abstract |
| Background and Aim: Tea (Camellia sinensis) contains bioactive compounds, including the relaxant L-theanine and the stimulant caffeine, as well as strong antioxidants. This study aimed to (1) explore the relationship between antioxidant activity and L-theanine/caffeine content in tea, and (2) assess how milk addition affects these compounds in white tea. Materials and Methods: In experiment one, white, green, and black teas were cold-infused (<10°C) for 5 min (1g/20ml W/V), filtered, and treated with polyvinylpolypyrrolidone (PVPP) to remove polyphenols. Antioxidant activity was measured using a DPPH radical scavenging assay, and L-theanine and caffeine contents were quantified via high-performance liquid chromatography (HPLC). In experiment two, white tea extracts were prepared similarly and mixed with 0%, 10%, 20%, or 50% (V/V) partly skimmed milk (2% fat). After refrigeration (∼4°C, 20 min), samples were analyzed via HPLC. All analyses were done in triplicate, using methanol/water (25:75% V/V) as the mobile phase at 1 ml/min. Statistical significance was set at p < 0.05. Results: White, green, and black teas exhibited varying antioxidant activity and compound levels. Black tea had the lowest L-theanine (0.31±0.017 mg/ml) and caffeine (0.106±0.004 mg/ml) but a high L-theanine-to-caffeine ratio, correlating with strong antioxidant activity (85±0.23%). In white tea, milk addition reduced caffeine significantly—by ~17% and 42% with 10% and 20% milk, respectively. The highest L-theanine-to-caffeine ratio (2.37±0.46) occurred in 20% milk samples. Conclusion: Antioxidant activity in tea is linked to its L-theanine-to-caffeine ratio, which can be modified through extraction methods. Tailoring tea infusions to increase L-theanine while reducing caffeine may benefit individuals seeking relaxation without stimulation. |
| Keywords |
| Tea, Camellia sinensis, L-theanine, Caffeine, Antioxidant activity, HPLC |
| Status: Accepted |
