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Whether a cup leans fresh-mellow or bold is no mystery — it depends on the balance of three substances: the polyphenols that make tea astringent and bitter, the caffeine that adds bitterness and lift, and the theanine that brings freshness and sweetness. Dial them yourself below:
Drag the three components, or pick a tea preset below, to see flavour and the polyphenol/amino-acid ratio change ↓
Illustrative model, not a precise measurement. The real "polyphenol/amino-acid ratio" is a key green-tea quality index — lower usually means fresher and mellower.
Raise theanine and lower polyphenols and the tea leans fresh-sweet (like shaded gyokuro); reverse it and it turns bold and astringent (like assamica for black tea). Their levels and ratio are the “mixing desk” of a tea’s style.
L2 · Deep DiveThe three leads and their tastes
- Polyphenols (mainly catechins): bring astringency and bitterness, tea’s “skeleton” and main antioxidants.
- Caffeine: brings bitterness and stimulation.
- Theanine & amino acids: bring freshness and returning sweetness, and soften the bitterness of polyphenols and caffeine.
Their absolute amounts set strength, while the ratio between them sets the style — and the most-used yardstick is the polyphenol/amino-acid ratio.
The key index: the polyphenol/amino-acid ratio
The ratio of polyphenol to amino-acid content is an important index of quality and style (especially for green tea):
- Low ratio → relatively more amino acids → fresh and mellow, ideal for fine green tea;
- High ratio → relatively more polyphenols → bold and astringent, better suited to black tea.
What lowers the ratio
Anything that relatively raises amino acids and curbs polyphenols lowers the ratio and makes tea fresher:
- Tender plucking: buds and young leaves are higher in amino acids, lower in polyphenols (early-spring buds taste fresher).
- Shading: suppresses the conversion of amino acids into polyphenols (gyokuro, matcha) — see leaf chemistry.
- High altitude / low temperature / spring: slower growth lets amino acids accumulate.
Conversely, strong sun, heat, summer and large-leaf cultivars tend to give a higher ratio, better for bold black tea.
Composition across the six tea types
The chart below gathers the typical dry-weight ranges of the main components across the six categories (synthesised from tea-biochemistry literature). Pick a component to compare the six teas:
Pick a component to compare its level across the six tea types (typical dry-weight ranges)
Full data:
| Component | Green | White | Yellow | Oolong | Black | Dark |
|---|---|---|---|---|---|---|
| Polyphenols | 22–30% | 18–25% | 20–26% | 15–25% | 8–15% | 5–12% |
| Catechins | 12–18% | 10–15% | 10–14% | 6–12% | 1–3% | <1% |
| Amino acids | 2–4% | 2.5–4.5% | 2–3.5% | 1.5–3% | 1–2.5% | 0.5–2% |
| Caffeine | 2.5–4% | 2.5–4% | 2.5–4% | 2–3.5% | 2.5–4% | 1.5–3% |
| Soluble sugars | 2–4% | 3–5% | 2.5–4% | 2–4% | 2–4% | 3–6% |
| Theaflavins | — | — | — | trace | 1–2% | — |
| Thearubigins | — | — | — | trace | 5–10% | trace |
| Theabrownins | — | — | — | — | 2–5% | 5–15% |
Values are typical ranges of dry-tea weight percentage and vary widely with cultivar, origin, plucking standard and process; theaflavins / thearubigins / theabrownins are products of oxidation and post-fermentation. Synthesised from Wan Xiaochun, Tea Biochemistry (3rd ed.), Chen et al. (2009), Wang et al. (2010), Xu et al. (2018), etc. [3][4]
See also
- The Flavour Chemistry of the Fresh Leaf — where the three substances come from
- The Flavour Wheel — how composition becomes specific aroma and taste
- Brewing Basics — how brewing also shifts the bitter/sweet balance
References
- Tea Components. O-CHA / World Green Tea Association. https://www.o-cha.net/english/cup/pdf/38.pdf
- Tea Polyphenols: Tastes and Tea Choices. Tea Guardian. https://www.teaguardian.com/tea-health/tea-polyphenols-tastes-tea-choices/
- Wan Xiaochun. Tea Biochemistry (3rd ed.). China Agriculture Press, 2003.
- Wang, K., et al. (2010). Comparison of catechins and amino acids in white, green, oolong, black, and pu-erh teas. Food Chemistry, 121(2), 338–344.
The interactive is an illustrative model, not a precise measurement; the real ratio uses measured polyphenol and amino-acid contents.