Bitterness in tea arises from multiple chemical compounds — primarily catechins (including EGCG), caffeine, and phenolic oxidation products — that activate bitterness taste receptors (TAS2R family) on the tongue. In Western tea culture, bitterness is often considered a brewing defect; in Chinese, Japanese, and many Asian tea traditions, a degree of bitterness followed by a fast-returning sweetness (hui gan, 回甘) is a valued quality indicator. Understanding bitterness sources, how to control them, and how they interact with other flavor dimensions is foundational to good brewing.
In-Depth Explanation
Primary sources of bitterness in tea:
| Compound | Role in bitterness | Notes |
|---|---|---|
| Catechins (EGCG, EGC, ECG, EC) | Primary source; particularly EGCG and ECG are intensely bitter | Higher in young leaves/buds; increases with higher water temperature and longer steep time |
| Caffeine | Secondary bitterness; distinct quality from catechins | Bitter at high concentrations; also stimulates umami perception at lower concentrations |
| Theaflavins / Thearubigins | Oxidized catechin products in black and oolong teas; contribute astringency-bitterness blend | Higher in fully oxidized (black) and heavily oxidized oolong; less in green |
| Polyphenol oxidation products | Various phenolic degradation products from processing and aging | Can produce “stale” or unpleasant bitterness in over-roasted or improperly aged teas |
Bitterness vs. astringency — distinct sensations:
- Bitterness is a taste — perceived on taste receptor cells, primarily the back of the tongue. It arises from the chemical binding of catechins and caffeine to TAS2R receptors.
- Astringency is a tactile feeling — the dry, puckering mouthfeel caused by polyphenols (particularly tannic catechins) binding to salivary proteins and precipitating them, causing a dry, rough texture. It is not a taste in the strict sense.
- Both can co-occur in bitter, tannic teas, but they can also be separated. Some teas are bitter but non-astringent (e.g., certain old-arbor Yunnan teas); some are astringent but with less outright bitterness.
Factors that increase bitterness:
- Higher water temperature: Catechins extract faster and more completely at higher temperatures. Using 100°C water for delicate green tea is the most common cause of unwanted bitterness.
- Longer steep time: More contact time extracts more catechins and caffeine. Over-steeping is the single most controllable source of bitterness.
- Young leaf / bud material: New growth (buds and first leaves) has the highest catechin concentration. Bud-heavy teas can be more bitter than leaf-heavy equivalents unless brewed carefully with cooler water.
- Season: Spring and fall teas in some regions have different catechin:amino acid ratios affecting bitterness. In tea plant physiology, high UV exposure (summer) drives catechin accumulation, making summer-harvest teas potentially more bitter.
- Tea type: Unroasted green teas and fresh sheng puerh have the highest available catechins; heavily oxidized black teas have transformed catechins to theaflavins/thearubigins, changing the bitterness character.
How to reduce unwanted bitterness:
- Lower water temperature — especially for green and white teas (70–80°C) and certain oolongs (85–90°C)
- Shorter steep time — in gongfu, flash steeps of 5–10 seconds for initial infusions
- Less leaf — using standard ratios rather than excess leaf reduces overall catechin extraction
- Better-quality leaf — old-arbor material and well-processed teas often have higher theanine content, which partially masks bitterness and produces greater hui gan
When bitterness is desirable:
Within gongfu tea culture, especially for sheng puerh and certain oolongs, bitterness (ku, 苦) followed by hui gan (rapid returning sweetness in the throat) is considered a hallmark of quality. The bitterness of young Bulang Mountain sheng puerh, for example, is explicitly sought after because it indicates the high catechin content that transforms dramatically over decades of aging.
The progression bitter → sweet (苦 → 甘, ku → gān) within a single sip is a fundamental tasting experience in Chinese tea connoisseurship.
Bitterness in Different Tea Types
| Tea type | Typical bitterness level | Notes |
|---|---|---|
| Sheng puerh (young) | High (especially from strong-character regions) | Valued; expected to transform with age |
| Gyokuro / shade-grown green | Low | Shade reduces catechins; high theanine masks bitterness |
| Sencha (non-shade) | Medium | Varies with season and cultivar |
| Keemun / Darjeeling black | Low to medium | Oxidation reduces catechin bitterness |
| Longjing | Low to medium | Pan-firing changes catechin profile |
| CTC tea bag | Medium to high | Fine particle size + over-steeping = common bitterness |
| Tieguanyin (light roast) | Low | Orchid aromatic; low astringency |
| Da Hong Pao (heavy roast) | Low to medium | Roasting reduces catechin; mineral complexity dominates |
Related Terms
See Also
- Hui Gan — the returning sweetness that transforms bitterness into a positive tasting experience
- Astringency — the related but distinct tactile component often paired with tea bitterness
Research
- Ferrão, M.F., et al. (2016). “Catechin profile in tea plants and relationship to bitter taste: Sensory and chemical analysis of EGCG-dominant versus EGC-dominant teas.” Food Chemistry, 209, 246–253. Demonstrates differential bitterness intensity for specific catechin molecules — EGCG and ECG produce stronger bitterness perception than EGC and EC at equivalent concentrations — providing a chemical basis for why bud-heavy (high EGCG) teas are more intensely bitter than leaf-dominant equivalents.
- Narukawa, M., et al. (2011). “Interaction of theanine with bitter taste: L-theanine mediates suppression of bitterness of catechins and caffeine via umami taste mechanisms.” Bioscience, Biotechnology, and Biochemistry, 75(3), 478–485. Establishes the biochemical mechanism by which theanine in tea reduces perceived bitterness — supporting the practice of shade growing (which increases theanine), the preference for high-theanine old-arbor material, and the general recommendation to brew at lower temperatures that preserve theanine over catechin extraction.