guaiacol
compound / compound-guaiacol
グアヤコール / 2-methoxyphenol
Guaiacol is a smoke-derived phenolic compound. Produced from the thermal decomposition of wood lignin, it is one of the principal components that characterize the aroma of many smoked foods and smoke teas.
On this page (8 sections)
Reading the bitterness
Guaiacol (2-methoxyphenol) is a smoke-derived phenolic compound produced from the thermal decomposition of wood lignin and is known as a component that characterizes the aroma of many smoked foods. In a study analyzing the aroma components of bonito flake katsuobushi, guaiacol was identified as one of the top 10 components by aroma contribution, with FD (Flavor Dilution) factor 15625 and concentration 9.12 ppm. In the same extract, syringol (256 ppm, FD factor 3125) has the highest concentration, yet guaiacol exceeds it in contribution degree, demonstrating that aroma 『濃さ』 (in translation: "intensity") and 『効き方』 (in translation: "sensory impact") do not necessarily coincide. However, this evaluation is limited to GC-MS/olfactometry and orthronasal sensory evaluation by a professional chef, and reference to or measurement of bitterness as a taste characteristic is not found in the original paper.
A study evaluated 19 smoky phenolic compounds including guaiacol, in which a highly trained panel assessed aroma intensity using 11 aroma attributes including smoky, ashy, woody, and burnt. This evaluation was performed using olfactometry with fragrance strips, i.e., olfaction alone, and taste attributes including bitterness were not included in the measurement targets. A related separate paper explicitly states that bitter, metallic, and sour are included among the original 14 terms representing smoked flavor, yet the actual evaluation table comparing 34 binary combinations never once includes bitter scores. This represents an important observation in the literature: 『燻香＝苦味』 (in translation: "smoked aroma = bitterness") cannot be directly assumed.
Rather, guaiacol has been reported as a candidate on the bitterness-suppressing side. A 2026 study (abstract stage) targeting black tea 「正山小種」 (Lapsang Souchong) produced by withering in pine smoke reports that guaiacol antagonistically inhibited the activation of bitter taste receptor TAS2R14 induced by tea extract before withering, reducing intracellular calcium signal by 37 percent. Quantum chemical calculations suggest non-covalent interactions through hydrogen bonding and van der Waals forces. However, this is information from a single study at the abstract stage, and due to the nature of a cell-level assay, extrapolation to human sensory evaluation is not direct.
Sources for this overview
Aroma Compounds Contributing to Dried Bonito（かつお節の香りに寄与する重要香気成分）
Checked for this overview: Cited the numerical findings from bonito flake aroma contribution analysis as evidence for paragraph 1.
Checked for this overview: Cited the point that aroma attribute evaluation is limited to olfaction as evidence for paragraph 2.
Checked for this overview: Cited the fact that bitter is not included in the scale as evidence for paragraph 2.
Role of smoke withering process in the bitterness amelioration effect on smoked Lapsang Souchong tea
Checked for this overview: Cited the abstract-stage content of TAS2R14 antagonistic inhibition as evidence for paragraph 3.
Follow the connections
katsuobushi (smoked-dried bonito) →contains→ guaiacol
guaiacol →antagonizes→ TAS2R14
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
Composition and content (1)
Scope: Supercritical CO2-extracted raw bonito flake katsuobushi, with the top 10 components by aroma contribution selected by AEDA (Aroma Extract Dilution Analysis) method
Note: Guaiacol (2-methoxyphenol) was identified with FD (Flavor Dilution) factor 15625 and concentration 9.12 ppm as the component with the highest aroma contribution. In the same extract, syringol (2,6-dimethoxyphenol) showed the highest concentration at 256 ppm but an FD factor of only 3125, exemplifying that aroma 「強さ(濃度)」 (in translation: "intensity (concentration)") and 「寄与度(希釈感度)」 (in translation: "sensory contribution (dilution sensitivity)") do not correspond. Evaluation was performed by GC-MS/olfactometry and orthronasal sensory evaluation by a professional chef, both limited to aroma (olfactory) assessment. Reference to or measurement of taste characteristics including bitterness is not found in the original text.
Show data
ingredient-katsuobushi —contains→ compound-guaiacolSensory (1)
Scope: Aroma-intensity evaluation, by a highly trained panel, of 19 smoke-associated phenol, guaiacol, and syringol derivatives, including guaiacol and syringol themselves, both singly and in two-compound combinations (2 studies)
Note: The second paper states explicitly that the original 14 terms for smoke flavor proposed by Jaffe and colleagues include bitter, metallic, and sour, but a bitterness score never appears in the actual evaluation tables (Tables 1-5 of each paper). All evaluation was done by smelling (fragrance strips/olfactometry), and no taste evaluation (tasting in the mouth) was carried out. This is an important observation in the literature, guarding against silently assuming that 「燻香=苦味」 (in translation: "smoke aroma equals bitterness").
Show data
compound-guaiacol —is_documented_as_having→ "An aroma profile characterized by 11 aroma attributes — smoky, ashy, woody, musty/dusty, musty/earthy, burnt, acrid, pungent, petroleum-like, creosote/tar, and cedar — over a concentration range of 1 to 100,000 ppm, rated on a 15-point intensity scale"Mechanism and receptors (1)
Scope: A cell-based assay using 「正山小種」(Lapsang Souchong) tea extract before the pine-smoke withering process as the index of TAS2R14 activation.
Note: Guaiacol has been reported to antagonistically inhibit TAS2R14 activation induced by tea extract from Lapsang Souchong before the pine-smoking withering process in the form of reducing intracellular calcium signal by 37 percent. Quantum chemical calculations suggest non-covalent interactions through hydrogen bonding and van der Waals forces. This is information from a single study at the abstract stage, and the full text has not been confirmed.
Show data
compound-guaiacol —antagonizes→ receptor-tas2r14