Characterizing Six Commercially‐Available Teas for Polyphenol Content and Antioxidative Capacity in Relation to Steep Time
Bibliographic record
Abstract
Globally, tea is the most commonly consumed beverage after water and is associated with many health benefits. These health benefits are often attributed to the unique profile and abundance of polyphenols in tea. In vivo , polyphenols have been shown to exhibit antioxidant activity and are thus capable of inhibiting free radical production. The purpose of this study was to characterize six popular and commercially available teas in terms of total polyphenolic content (TPC) and relative antioxidant capacity after varying the steep times. Dragonwell (DW), Japanese Sencha (JS), English Breakfast (EB), Golden Monkey (GM), Green Rooibos (GR), and Red Rooibos (RR) loose leaf teas were individually steeped in water for 5 or 10 minutes at the manufacturer's recommended temperature (79°C for DW, JS; 96°C for EB, GM, GR, RR) to extract polyphenols. TPC was determined using Folin‐Ciocalteau's reagent with Gallic acid as a standard; and antioxidative capacity was determined by the ability of a normalized amount of polyphenols (1μg/ml) from each tea to scavenge the free radical 2, 2‐diphenyl‐1‐picrylhydrazyl (DPPH). TPC was observed to be significantly greater (p<0.05) after 10 minutes of steeping than it was after 5 minutes for each of the teas. However, 66–73% of polyphenols measured at 10 minutes were extracted in the first 5 minutes (% of total TPC extracted: DW=66.08±6.36, JS=73.37±3.08, EB=71.74±4.74, GM=65.40±2.69, GR=68.31±3.17, RR=71.14±5.95) regardless of tea type. After 5 minutes of steeping, significant differences (p<0.05) in TPC were observed among different teas (JS~EB>DW>GM~GR~RR). Different teas with their respective polyphenol profiles also varied (p<0.05) in their ability to inhibit the free radical DPPH (% inhibition: DW>JS~EB~GM>GR>RR). In summary, TPC varies greatly among types of tea, but the majority of polyphenols are extracted after 5 minutes of steeping regardless of tea type. The wide range in the ability of the different teas to scavenge free radicals, even after normalizing for TPC, indicates an important role for the specific polyphenol profile and potential different health benefits among teas. Support or Funding Information NSERC
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".