日本語版

epigallocatechin gallate

compound / compound-egcg

エピガロカテキンガレート（EGCG）

Epigallocatechin gallate is a gallate-type tea catechin abbreviated EGCG.

On this page (7 sections)
  1. Overview
  2. Sources for this overview (7)
  3. Topic hubs
  4. Follow the connections
  5. Related entries (10)
  6. Sensory (5)
  7. How processing and cooking change it (2)
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Reading the bitterness

In sensory evaluations by concentration targeting green-tea infusions, epigallocatechin gallate (EGCG) concentration was one of two catechin markers that correlated strongly with bitterness. This correlation was specific to the infusion used and measurement conditions. In a separate study using cultured cells expressing human TAS2R39, a clear response to 300 micromolar EGCG was observed (second in strength to epicatechin gallate), and EGCG and epicatechin gallate are identified as 「ヒトで強い苦味を誘発する」 (in translation: catechins that induce strong bitterness in humans). This receptor-level finding is independent evidence from the sensory data of concentration-bitterness correlation, and both types of evidence reinforce the connection between EGCG and bitterness from different angles.

In taste-reconstruction research on black tea, the reduced reconstitution system of key compounds explicitly included 「収斂性(渋み)かつ苦味のエピガロカテキン-3-ガレート」 (in translation: "the astringent and bitter epigallocatechin-3-gallate"), distinguished from the velvety-astringent flavonol-3-glycosides and the puckering-astringent catechins. Even if EGCG carries both bitterness and astringency, this description indicates that they should be treated as separate sensations that co-occur.

Fresh green tea from Turkey was extracted at 75, 85, and 95°C for 1 to 45 minutes in an experiment; extraction at 95°C had lower EGCG concentration than at 85°C, attributed mainly to epimerization of EGCG to the non-epimeric form of gallocatechin gallate (GCG). Non-epimeric-form catechins (GCG, gallocatechin, catechin) continued to increase with temperature and time, reaching 3.63 mg per 100 mL of tea solution for GCG at 95°C for 45 minutes. In another independent study, when 「龍井」 (Longjing) tea catechin mixture and purified EGCG were autoclaved at 120°C for 20 minutes, epimerization of EGCG to the non-epimeric form GCG was observed, and the same chemical transformation of EGCG to the non-epimeric form by high-temperature heating was confirmed in different materials and temperature ranges.

In measurements using an electronic tongue, the response to bitterness intensity of major gallate-ester-type catechins in green tea (EGCG, ECG, GCG) is reported to be suppressed in a dose-dependent manner by umami amino acids theanine, glutamate, and aspartate. Theanine and glutamate interact more strongly with ester-type catechins than aspartate, with hydrogen bonding reported to be the main interaction force. However, the effect on astringency (electronic tongue response) is recorded as only 「複雑」 (in translation: complex) in the same study, and whether an increase or decrease direction predominates is not stated unambiguously.

In an analysis using tea from Kochi Prefecture, the deeper the roasting when processing into hojicha, the more the EGCG content per 100 mL of tea liquor decreased monotonically. For first-flush tea it went from 20.38 mg in the unrefined tea to 6.29 (light roast), 3.15 (medium roast) and 1.18 (deep roast); for second-flush tea from 34.33 to 10.29, 5.10 and 1.89. Epicatechin gallate decreased with the same trend, and both (EGCG and epicatechin gallate) are compounds recorded as gallate-type catechins that activate the TAS2R39 receptor; but how the decrease in content corresponds to a change in perceived bitterness cannot be confirmed from this source.

Sources for this overview

  1. Quantitative analyses of the bitterness and astringency of catechins from green tea

    Xu YQ; Zhang YN; Chen JX; Wang F; Du QZ; Yin JF / 2018 / journal article / abstract checked

    Checked for this overview: Used as the basis for the sensory data on correlation between EGCG concentration in infusions and bitterness

  2. Evaluation of the bitterness of green tea catechins by a cell-based assay with the human bitter taste receptor hTAS2R39

    Narukawa M; Noga C; Ueno Y; Sato T; Misaka T; Watanabe T / 2011 / journal article / abstract checked

    Checked for this overview: Used as the basis for the description of receptor response intensity at 300 micromolar

  3. Molecular definition of black tea taste by means of quantitative studies, taste reconstitution, and omission experiments

    Scharbert S; Hofmann T / 2005 / journal article / abstract checked

    Checked for this overview: Used as the basis for the taste-reconstruction description distinguishing bitterness and astringency as separate sensations

  4. Effects of different brewing conditions on catechin content and sensory acceptance in Turkish green tea infusions

    Saklar S; Ertas E; Ozdemir IS; Karadeniz B / 2015 / journal article / full text checked

    Checked for this overview: Used as the basis for measured EGCG and GCG values at different extraction temperatures

  5. Degradation of green tea catechins in tea drinks

    Chen Z; Zhu QY; Tsang D; Huang Y / 2001 / journal article / abstract checked

    Checked for this overview: Used as the basis for confirmation of epimerization by autoclaving in different materials

  6. Interaction between major catechins and umami amino acids in green tea based on electronic tongue technology

    Liu Zhongying; Ran Qiansong; Li Qin; Yang Ting; Dai Yuqiao; Zhang Tuo; Fang Shimao; Pan Ke; Long Lin / 2023 / journal article / abstract checked

    Checked for this overview: Used as the basis for the description of bitterness suppression by umami amino acids measured by electronic tongue / Used as the basis for the limitation statement that the effect on astringency is complex and not unambiguous

  7. 焙煎程度とほうじ茶の品質

    高知県農業技術センター茶業試験場 / / government document / full text checked

    Checked for this overview: Used as the basis for the entire paragraph on measured EGCG and ECG values at different roasting degrees

Follow the connections

epigallocatechin gallate →is correlated with→ bitterness →can be measured separately …→ astringency

epigallocatechin gallate →— electronic-tongue bittern…→ L-theanine

hojicha roasting →reduces→ epigallocatechin gallate

Hypotheses and recipe candidates for this entry are on the Japanese page.

Structured claims — open a section to read each claim's confidence, evidence and limits

Sensory (5)

epigallocatechin gallate is correlated with bitternesssupported

Scope: Green tea infusion in the cited quantitative study.

Note: The correlation is specific to concentration and matrix.

In modeled infusions, EGCG concentration was 1 of 2 catechin markers that correlated strongly with bitterness.
Limitations: Correlation specific to the study.
Source: Quantitative analyses of the bitterness and astringency of catechins from green tea (Xu YQ; Zhang YN; Chen JX; Wang F; Du QZ; Yin JF, 2018) · abstract checked
Cultured cells expressing hTAS2R39 showed a clear response to 300 µM EGCG (second in strength to ECG). The abstract positioned ECG and EGCG as 「ヒトで強い苦味を誘発する」 (in translation: catechins that induce strong bitterness in humans), providing mechanistic support at the receptor level. This is independent (receptor assay) support from Xu 2018's concentration-bitterness correlation (sensory evaluation).
Limitations: The response reported in the abstract is at a single concentration (300 µM). Receptor activation is a proxy for human sensory intensity, not a quantification of EGCG bitterness itself.
Source: Evaluation of the bitterness of green tea catechins by a cell-based assay with the human bitter taste receptor hTAS2R39 (Narukawa M; Noga C; Ueno Y; Sato T; Misaka T; Watanabe T, 2011) · abstract checked
Show datacompound-egcg —is_correlated_with→ sensation-bitter
claim: clm-egcg-bitter / type: sensory / updated: 2026-08-30
epigallocatechin gallate190 µmol/L (derived value: stated as 190,000 times the detection threshold of quercetin-3-O-rutinoside 0.001 µmol/L) has an astringency threshold of: supported

Scope: Human astringency threshold in black-tea research

Note: Value arithmetically derived from the ratio stated in the abstract. Values in the table were not directly verified (access only to abstract level).

The detection threshold of quercetin-3-O-rutinoside is stated as 0.001 µmol/L, which is 1 / 190,000th of the threshold determined for epigallocatechin gallate, implying that EGCG's astringency threshold is 190 µmol/L.
Limitations: The value was derived from the stated ratio, not read from a table, and the original threshold in the table was not verified.
Source: Identification of the astringent taste compounds in black tea infusions by combining instrumental analysis and human bioresponse (Scharbert S; Holzmann N; Hofmann T, 2004) · abstract checked
Show datacompound-egcg —has_astringency_threshold_of→ "190 µmol/L (derived value: stated as 190,000 times the detection threshold of quercetin-3-O-rutinoside 0.001 µmol/L)"
claim: clm-egcg-astringency-threshold / type: sensory / updated: 2026-08-30
epigallocatechin gallate — sensory attribute: astringency and bitterness both (Verbatim: the astringent and bitter epigallocatechin-3-gallate)supported

Scope: Black-tea taste-reconstitution system. Contrasted with velvety-astringent flavonol-3-glycosides and puckering-astringency catechins.

Note: Supports treating EGCG's bitterness and astringency as co-occurring but separate sensory qualities.

In the condensed-key-compounds reconstitution system, epigallocatechin-3-gallate with astringency and bitterness was explicitly included, distinguished from velvety-astringent flavonol-3-glycosides and puckering-astringency catechins.
Limitations: From abstract text; intensity values by quality are unverified.
Source: Molecular definition of black tea taste by means of quantitative studies, taste reconstitution, and omission experiments (Scharbert S; Hofmann T, 2005) · abstract checked
Show datacompound-egcg —has_sensory_attribute→ "astringency and bitterness both (Verbatim: the astringent and bitter epigallocatechin-3-gallate)"
claim: clm-egcg-astringent-and-bitter / type: sensory / updated: 2026-08-30
epigallocatechin gallate — electronic-tongue bitterness response was reduced by: L-theaninesupported

Scope: Electronic tongue measurement targeting major galloylated catechins of green tea (EGCG, ECG, GCG). Tested with theanine, glutamate, and aspartate

Note: Glutamate and aspartate have also been reported to inhibit the electronic tongue response to bitterness intensity in a concentration-dependent manner. This is based on electronic tongue (instrument) response values, not confirmation by human sensory panel. Theanine and glutamate interact more strongly with galloylated catechins than aspartate does, and hydrogen bonding is reported to be the main interactive force.

Reported that umami amino acids (theanine, Glu, Asp) inhibit electronic tongue response to bitterness intensity of galloylated catechins in a concentration-dependent manner
Limitations: Electronic tongue instrument response, not verification by human sensory panel. Experiment used purified single catechin solutions, not matcha itself.
Source: Interaction between major catechins and umami amino acids in green tea based on electronic tongue technology (Liu Zhongying; Ran Qiansong; Li Qin; Yang Ting; Dai Yuqiao; Zhang Tuo; Fang Shimao; Pan Ke; Long Lin, 2023) · abstract checked
Show datacompound-egcg —has_e_tongue_bitterness_reduced_by→ compound-l-theanine
claim: clm-egcg-etongue-bitterness-theanine / type: sensory / updated: 2026-09-02
epigallocatechin gallate — combined bitter-astringent taste is affected by: Co-presence with umami amino acids (theanine, glutamic acid, aspartic acid). The source reports that bitterness was suppressed in a concentration-dependent manner, whereas the effect on astringency (electronic-tongue response) was not uniform and was described as complicated.preliminary

Scope: Same as above (Liu et al. 2023); an electronic-tongue study.

Note: The source text describes the effect on astringency only as ‘complicated’, without unambiguously stating whether increase or decrease predominates. This is confirmed from the abstract only; the details in the body text (numeric values, direction by condition) have not been read.

Limits: The effect of umami amino acids on the astringency response of the ester-type catechin is described as ‘complicated’, and does not show as simple a suppressive direction as bitterness does.
Limitations: Based on the abstract only; specific numeric values and directionality are unclear.
Source: Interaction between major catechins and umami amino acids in green tea based on electronic tongue technology (Liu Zhongying; Ran Qiansong; Li Qin; Yang Ting; Dai Yuqiao; Zhang Tuo; Fang Shimao; Pan Ke; Long Lin, 2023) · abstract checked
Show datacompound-egcg —has_bitter_astringency_affected_by→ "Co-presence with umami amino acids (theanine, glutamic acid, aspartic acid). The source reports that bitterness was suppressed in a concentration-dependent manner, whereas the effect on astringency (electronic-tongue response) was not uniform and was described as complicated."
claim: clm-egcg-astringency-amino-acid-complicated / type: sensory / updated: 2026-09-02

How processing and cooking change it (2)

epigallocatechin gallate epimerizes to: Non-epi-form gallocatechin gallate (GCG) during high-temperature extraction. The main reason EGCG was lower at 95 C extraction than at 85 C was this epimerization.supported

Scope: Turkish green tea extracted at 75/85/95 C for 1-45 minutes. GCG, GC, and C continued to increase with temperature and time (GCG reaching a maximum of 3.63 mg/100 ml at 95 C, 45 minutes).

Note: A single tea material (fresh Turkish green tea). The authors note that leaf age, size, season, and manufacture affect the results.

Extraction at 95 C gave a lower EGCG concentration than at 85 C, attributed mainly to epimerization from EGCG to the non-epi-form GCG; the non-epi-form catechins (GCG, GC, C) continued to increase with temperature and time, reaching GCG 3.63, GC 7.33, and C 2.31 mg/100 ml at 95 C, 45 minutes.
Limitations: A single tea material; the authors note that leaf age, leaf size, season, and manufacturing conditions affect the results.
Source: Effects of different brewing conditions on catechin content and sensory acceptance in Turkish green tea infusions (Saklar S; Ertas E; Ozdemir IS; Karadeniz B, 2015) · full text checked
An independent lab (Chinese University of Hong Kong): autoclaving a Longjing tea catechin mixture and pure EGCG at 120 C for 20 minutes was observed to cause epimerization from EGCG to GCG (gallocatechin gallate). "The relatively high amount of GCG found in some tea drinks was most likely the epimerization product of EGCG during autoclaving." Boiling at 98 C for 7 hours degraded 20% of GTC. This independently confirms, in a different material and temperature range, the same chemistry as Saklar 2015's finding at 95 C extraction that EGCG converts to the non-epi-form GCG under high-temperature heating.
Limitations: Abstract only. The direct observation of epimerization is under autoclave conditions at 120 C; the abstract does not state the epimerization rate in the boiling temperature range of 95 C or below. No sensory data.
Source: Degradation of green tea catechins in tea drinks (Chen Z; Zhu QY; Tsang D; Huang Y, 2001) · abstract checked
Show datacompound-egcg —epimerizes_to→ "Non-epi-form gallocatechin gallate (GCG) during high-temperature extraction. The main reason EGCG was lower at 95 C extraction than at 85 C was this epimerization."
claim: clm-egcg-epimerizes-to-gcg-hot-brewing / type: processing / updated: 2026-08-30
hojicha roasting reduces epigallocatechin gallatesupported

Note: Epigallocatechin gallate and epicatechin gallate are recorded in NIGAMI LAB's existing records as gallate-type catechins that activate the human bitter receptor TAS2R39. However, this Kochi Prefecture source measures only compound levels, and how the decrease in compounds from roasting corresponds to a change in bitterness perception cannot be confirmed from this source.

Measured values from the epigallocatechin gallate and epicatechin gallate rows of Table 1. In every flush, the values decrease monotonically as roast degree deepens from crude tea → light roast → medium roast → deep roast.
Limitations: A single-year (2013) trial on Kochi Prefecture tea. It measures compound levels, and this source does not link them to a sensory evaluation.
Source: 焙煎程度とほうじ茶の品質 (高知県農業技術センター茶業試験場) · full text checked
Show dataprocess-hojicha-roasting —reduces→ compound-egcg
claim: clm-hojicha-egcg-ecg-decrease / type: processing / updated: 2026-09-02

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