Identification: Identified as labelled in the source.
Image shown: The full-size file from Wikimedia Commons, reduced to 2400 px on the long side with sips. No cropping or color changes by NIGAMI LAB (resizing only). For display, a WebP capped at 1200 px wide is served; the ledger's original image can be checked from the link above.
A study of medium- and dark-roasted Arabica coffee using TDS (temporal dominance of sensations) and intranasal PTR-ToF-MS measurements showed that the temporal pattern of dominant flavors during drinking differs by roast level. Bitterness and roasted aroma dominated periods of the medium roast, whereas bitterness and burnt aroma dominated the dark roast. Only 1 level of roasting conditions was examined for each, however, and the 『優勢率』 (“dominance rate”) shown by TDS is not a measure of sensory intensity itself.
An analysis of Arabica green beans from Doi Chaang in Chiang Rai Province, Thailand (honey process; cup score above 80) found that as roasting increased from light to medium to dark, total phenolic content decreased (significantly in dark roast) and chlorogenic acid content also fell (no significance is stated for it), whereas caffeic acid, a breakdown product, increased. The lightness (L* value) of roasted beans correlated, according to the study, positively with chlorogenic acid content and negatively with caffeic acid content. The study was limited to 1 lot from a single farm and did not include human sensory evaluation.
A report analyzing volatile compounds in the same Doi Chaang Arabica by HS-SPME-GC/MS discusses changes in furfuryl alcohol content with roast level in connection with a description in other literature of 『焦げた・ロースト香が苦味として知覚される』 (“burnt and roasted aromas being perceived as bitterness”) arising through the Maillard reaction. This link appears in the discussion; the study itself did not measure bitterness in people.
Lourith N; Kanlayavattanakul M / 2025 / journal article / full text checked
Checked for this overview: Confirmed decreases in total phenolics and chlorogenic acid and an increase in caffeic acid as roast level rose. / Confirmed the discussion’s description of changes in furfuryl alcohol and 『苦味として知覚される』 (“perceived as bitterness”).
coffee roasting is associated with bitternesscontextual
Scope: Volatile compound analysis of Doi Chang-grown arabica (HS-SPME-GC/MS, comparing light, medium, and dark roasts)
Note: The body of the paper connects the change in furfuryl alcohol content with roast level to a description, via the Maillard reaction, that 「焦げた・ロースト香が苦味として知覚される(perceived as a bitter taste)」. However, this description is a discussion grounded in other literature, not the study's own human sensory measurement, so it is treated as contextual.
Context: "The level of roasting directly impacted the furfural alcohol content...in harmony with a relatively burnt or roasted odour perceived as a bitter taste with a more caramelized aroma observed due to the Maillard reaction achieved with roasting."
Limitations: This study did not conduct a human sensory (bitterness) panel. "bitter taste" is a discussion-level expression grounded in other literature, not the study's own measured result.
coffee roasting can change Sensory bitterness score (rated by 12 trained assessors holding Q Arabica Grader certification; the methods section does not state the range of the scale)supported
Scope: Ethiopian arabica beans; comparison of ultra-high-pressure-processed cold brew and conventional cold brew
Note: As roast degree deepened from Agtron color value 73 (light) → 62 (medium) → 53 (dark), the bitterness score increased significantly (ultra-high-pressure: 2.00±0.10 → 3.35±0.30 → 5.50±0.40; conventional: 3.00±0.28 → 4.30±0.42 → 6.50±0.42; p<0.05 in both). This is an academic source that directly shows, with statistical significance from a human sensory panel, the relationship that deeper roasting means stronger bitterness. The same directional trend was confirmed regardless of extraction method (both of the 2 extraction conditions: ultra-high-pressure and conventional). Agtron 73, 62 and 53 are the color bands corresponding to light, medium and dark roast; the beans were purchased, and the roasting conditions are not described (checked against sections 2.1 and 2.7 of the source and corrected on 2026-10-21).
In an evaluation by 12 trained sensory assessors (holding Q Arabica Grader certification; the methods do not state the range of the scale, and the highest score in Table 5 is 8.50), the bitterness score increased significantly as roasting deepened across Agtron color values 73 → 62 → 53 (light → medium → dark roast) (ultra-high-pressure: 2.00±0.10 → 3.35±0.30 → 5.50±0.40; conventional: 3.00±0.28 → 4.30±0.42 → 6.50±0.42; p<0.05).
Limitations: An experiment using a single origin and a single bean lot. The result is limited to the extraction condition (cold brew); generalizing to hot brew is outside the scope of this paper.
Scope: Chapter 7 (the chemistry of coffee's taste) of the SCA's official Coffee Sensory and Cupping Handbook (2021)
Note: Text read in an unofficial copy in 2026-09: "Sourness is preponderant in light roasts and bitterness in dark roasts." "bitterness actually increases with the roast level". It explicitly states that caffeine is only one part of coffee's bitterness compounds, and that bitterness increases even though caffeine decreases with roasting ("caffeine ... only accounts for a small percentage of coffee's bitterness"). (2026-10-22: the supporting source was lowered. The official edition could not be read and the public description does not mention bitterness, so the status moved from established to preliminary.)
Context: The official (paid) edition was not read. The SCA announcement only introduces the handbook as covering the perception of taste, aroma and texture from chemical, physiological and neural angles; it says nothing about bitterness or roast level.
Limitations: The description of bitterness in chapter 7 was read in 2026-09 in an unofficial copy and cannot be confirmed from the official edition or any public text. Because the copy's origin could not be confirmed, its standing was lowered (10/22).
Scope: Comparison of light roast (180°C), medium roast (200-220°C), and dark roast (230°C); total phenolic content quantified by the Folin-Ciocalteu method, and chlorogenic acid and caffeic acid quantified by UPLC
Note: The lightness L* value correlated positively with chlorogenic acid content (r=+0.9101) and negatively with caffeic acid content (r=-0.9360). This is a single lot (n=1) from a single farm, and no human sensory panel was conducted.
"High roasting level decreased the TPC, which was significantly (p<0.01) lower in dark-roasted coffee than in medium and light-roasted coffee...The chlorogenic acid content decreased with roasting, while in turn, the content of its degradation product, caffeic acid, was increased."
Limitations: Only a single lot (n=1) from a single farm. No human sensory panel was conducted.
Context: As an independent confirmation using a different origin and a different analytical method (UV-Vis), this study too reports a finding in the same direction: 『焙煎の熱によりクロロゲン酸が分解し、生豆より焙煎豆でCGA含量が下がる』 (in translation: "the heat of roasting breaks down chlorogenic acid, so CGA content is lower in roasted beans than in green beans"). However, this is not the study's own original elucidation of the mechanism but an interpretation citing Belay and Gholap (2009).
Limitations: The analytical method (UV-Vis) differs from the chromatography-based analysis of the Doi Chang study, and the breakdown of roast levels (light/medium/dark) is not reported either, so this remains a reproduction of the trend and does not allow a direct quantitative comparison.
coffee roasting is graded by: The "Agtron Roast Color Kit" officially distributed by the SCA (Specialty Coffee Association). It consists of 8 color disks housed in a white vinyl case, numbered in 10% increments from "Very Light" (tile #95) to "Very Dark" (tile #25).contextual
Scope: Product description on the SCA's official store
Note: The SCA's own official description of a visual reference tool it distributes. The accompanying manual is authored by Carl Staub. It is positioned not as an academic definition of roast level but as an industry consensus-building tool for roasters and customers to reach a shared understanding of roast level.
Describes 8 color disks, numbered in 10% increments ranging from Very Light (tile #95) to Very Dark (tile #25), and states that these 8 industry-standard disks are designed to enhance consistency and ensure that roasters and their customers agree on degree of roast.
Limitations: This is a description of an instrument, not a classification basis backed by chemical or sensory data.
coffee roasting is graded by: According to trade-press reporting, SCA may use a 「universal roasted arabica coffee color curve(普遍的な焙煎アラビカコーヒーの色曲線)」 (“universal roasted arabica coffee color curve”) identified by UC Davis Coffee Center research (7 roast profiles × 3 origins = washed Ugandan, washed Indonesian, and honey-process Central American; 663 samples and 39 experimental roasts; measured in L*a*b* color space) to develop a roast-color standard based on visible-light measurement. The trade publication reports that SCA published a white paper in that direction and is developing a draft.preliminary
Scope: At the time of the UC Davis Coffee Center research announcement and the trade-press report on the SCA white paper.
Note: This research is at the proposal stage toward standardization, not an established new standard. The materials checked here did not state the procedure or timing for developing it. They also did not specify how existing Agtron 8-level classifications or terms such as French and Italian would be treated (separated into a research question in leads).
Using L*a*b* color space to measure 7 roast profiles × 3 origins, 663 samples, and 39 experimental roasts, the study reported a "universal roasted arabica coffee color curve" independent of roast profile and origin.
Limitations: Translating this curve into the terminology of an industry standard lies beyond the paper’s scope and is left to SCA’s separate standardization work.
The UC Davis Coffee Center color curve is introduced as a basis for standardization given the absence of universally accepted criteria for "light roast""medium roast""dark roast".
Limitations: A trade-press account. The article does not state the specific procedure or timing for developing the standard.
The article summarizes SCA’s publication of the white paper Developing Roast Color Standards for the Specialty Coffee Industry, its plan to adopt a roast-level scale based on visible-light measurement, and the development of a draft standard.
Limitations: The white paper itself was not checked. This is a summary in a weekly report; the article does not give the procedure or timing for development.
coffee roasting has a standardized vocabulary entry in The 8-stage roast-level terminology listed in the 「知る・楽しむ」 (in translation: "Learn and Enjoy") section of the All Japan Coffee Association's official website — light roast, cinnamon roast, medium roast, high roast, city roast, full city roast, French roast, and Italian roast.contextual
Scope: A column article on the All Japan Coffee Association's official website
Describes the names and characteristics of the 8 stages (light roast, 「黄色がかった小麦色」 (in translation: "a yellowish wheat color"); French roast, 「強い苦味と独特の香りが楽しめる」 (in translation: "you can enjoy its strong bitterness and distinctive aroma"); Italian roast, 「色は黒に近い。強い苦味と濃厚な味わい」 (in translation: "the color is close to black; a strong bitterness and a rich, deep flavor"); and others), together with the general rule 「一般的には浅炒りほど酸味が強く、深炒りになるほど苦味を感じるようになります」 (in translation: "in general, the lighter the roast, the stronger the acidity, and the deeper the roast, the more bitterness is felt").
Limitations: There is no correspondence with instrument measurements, and the bitterness descriptions are the association's own statements, unsupported by any sensory test.
Show dataprocess-coffee-roasting —has_standardized_vocabulary_entry_in→ (the claim sentence above)
claim: clm-ajca-8stage-terms / type: cultural / updated: 2026-09-02
coffee roastingThe term The 8 terms for roast level, 「light・cinnamon・medium・high・city・full city・French・Italian」 (light, cinnamon, medium, high, city, full city, French, and Italian), are described as recorded in William Ukers's book 『All About Coffee』 (1928). first appears in: contextual
Scope: An article on the official SCA site (by Peter Giuliano) introducing Ukers’s (1928) description.
The source states that William Ukers' famous 1928 book All About Coffee mentioned 8 roast levels: light, cinnamon, medium, high, city, full city, French, and Italian.
Limitations: Ukers’s original 1928 work itself was not accessed in this investigation.
Show dataprocess-coffee-roasting —has_term_first_appearing_in→ (the claim sentence above)
claim: clm-roast-terms-ukers-1928 / type: cultural / updated: 2026-09-02
coffee roasting — unresolved property: There is no universally agreed standard in the roasting industry for what "light roast," "medium roast," and "dark roast" mean; one roaster's "light roast" can even be darker than another roaster's "dark roast." The SCA itself states that terms carrying regional names, such as French, Italian, and Full City, can be "too arcane or flexible to be meaningful."supported
Scope: Concerns raised about roast-level terminology by the SCA, people connected with the UC Davis Coffee Center, and trade publications
Note: A peer-reviewed journal article (Anokye-Bempah et al. 2025) and multiple SCA official articles and trade-press articles independently raise the same concern. This fact calls into question the very premise that 「地域名のついた焙煎度呼称が実際にその地域の慣行を一意に指す」 (in translation: "a roast-level term carrying a regional name actually refers uniquely to that region's practice").
States: "there are no universally accepted industry standards for what is meant by 'light roast,' 'medium roast,' or 'dark roast'" and "Some roasters produce 'light roasts' that are darker than the 'dark roasts' produced by others"
Limitations: The paper itself is primarily concerned with color measurement using the L*a*b* color space; this quoted portion is background explanation.
The source states that there are no universally accepted standards for what is meant by light roast, medium roast, or dark roast, and that roasters currently communicate roast levels in any number of ways, such as using European and U.S.-derived conventional names like Full City or French.
Show dataprocess-coffee-roasting —has_unresolved_property→ (the claim sentence above)
claim: clm-roast-naming-no-universal-standard / type: cultural / updated: 2026-09-02
coffee roasting is presented as: Coffee historian Mark Pendergrast’s book 『Uncommon Grounds』 (1999) states of Europe in the past: 「フランス人・イタリア人・ポルトガル人・スペイン人は、アラビカに加えるようになったロブスタ特有の苦味を隠す、より深い焙煎を好んだ」 (“The French, Italians, Portuguese, and Spanish enjoyed darker roasts that hid some of the bitter-tasting robustas they now added to the arabica beans”). It also notes a north–south difference within Italy: 「南に行くほど焙煎は深くなる傾向があり、南部イタリア人はほとんど豆を炭化させる一方、北部イタリア人は中程度の焙煎を好んだ」 (“The farther south, the darker the roast tended to be, so that southern Italians nearly turned their beans to charcoal, while northern Italians enjoyed a moderate roast”).contextual
Scope: Pendergrast, 『Uncommon Grounds』, chapter "The European Coffee Scene", on Europe in the 1920s–30s.
Note: This is a cited general book on coffee history, not a peer-reviewed academic paper. The page number in the original book has not been checked (the passage was verified through a site reproducing the full text). This passage alone cannot establish whether today’s retail terms 「イタリアン・ロースト」「フレンチ・ロースト」 (“Italian roast” and “French roast”) descend directly from those historical regional practices (separated into a research question in leads).
The source states that the French, Italians, Portuguese, and Spanish enjoyed darker roasts that hid some of the bitter-tasting robustas they now added to the arabica beans. It also states that the farther south, the darker the roast tended to be, so that southern Italians nearly turned their beans to charcoal, while northern Italians enjoyed a moderate roast.
Limitations: This is not peer-reviewed academic research. The page number in the original book has not been checked.
Show dataprocess-coffee-roasting —is_presented_as→ (the claim sentence above)
claim: clm-pendergrast-europe-dark-roast-robusta / type: cultural / updated: 2026-09-02
coffee roasting — historical origin: The so-called "Nordic light roast" style traces back to specific, named individual roasters — Tim Wendelboe, who opened a roastery in Oslo, and Klaus Thomsen, co-founder of Copenhagen's Coffee Collective, among them. Wendelboe recounts that the turning point was noticing that his own roasted beans tasted burnt compared with the coffee samples brought in by exporters. Thomsen himself, while saying he does not like the term "Nordic roasting," acknowledges that this approach itself — roasting as light as possible and holding back coffee's inherent development — carries major worldwide influence.contextual
Scope: Interviews (2023) with specialty coffee roasters in Norway and Denmark
Note: A 2023 interview article from the trade publication Perfect Daily Grind. Note that while the roasting style itself carrying the regional name "Nordic" traces back to specific roasters and a specific period, the person who established the style himself voices disagreement with that very regional-name label. Whether a term carrying a regional name uniquely refers to that region's practice is not generalized here.
Records Wendelboe's remarks describing the trigger for his shift in roasting style, Thomsen's remark to the effect that he does not like the term Nordic roasting, and his remark acknowledging the approach's own worldwide influence.
Limitations: This is an interview article, based on the retrospective accounts of the people involved.
