coffee brew
ingredient / ingredient-coffee-brew
コーヒー（抽出液）
Coffee brew is a beverage made by grinding roasted beans and extracting the components in water or hot water. Bitterness arises not only from caffeine but is rearranged by roasting byproducts and extraction conditions.
Photographs (captions in Japanese)
コーヒー抽出液の原料となる焙煎豆。写真の原典には種・品種・焙煎度が記されていないため、抽出後の液体そのものの色や濃度を示す写真ではない。
原料写っているもの: Coffea spp.（種・品種は原典未記載）部位・状態: 焙煎された種子
写真: MarkSweep／ Public domain／ 原画像／ 台帳の原画像
写真の範囲と来歴
被写体の確認: 原典の記載による同定。図鑑項目との関係は原料。抽出液そのものではない。
掲載画像: Wikimedia Commons の原寸ファイル。苦味研究所では切り抜き・色調変更なし。 表示用には幅1200px上限のWebPを配信し、台帳の原画像は上のリンクから確認できます。
On this page (8 sections)
Reading the bitterness
The photograph shows roasted beans, but the subject of this entry is a single cup of coffee made by grinding them and extracting the components in water or hot water. As the roasting method and the conditions for passing the hot water through the ground coffee vary, so too does the assembly of bitterness that reaches the cup. This bitterness cannot be explained by the word caffeine alone; multiple component groups are involved, including quinides, oligomers of 4-vinylcatechol, and mozambioside roasting byproducts.
For this reason, it is not possible to determine the bitterness of the extracted liquid on the basis of the bean name alone. Roasting conditions change the generation of bitter compounds, and the manner in which hot water passes through changes the amount of those compounds that reach the cup. Which candidate appears strongest is also influenced by the analytical method, and instrument taste-sensor responses cannot be equated with the breakdown of bitterness perceived by humans.
Nor is taste sensation on the drinking side fixed. In a trial with 155 subjects, a change occurred immediately after drinking coffee in which sweetness perception increased and bitterness perception decreased; this change was repeated even in decaffeinated coffee. In large-scale genetic statistics, bitterness sensitivity to quinine and PROP was negatively related to coffee intake, while bitterness sensitivity to caffeine was positively related. Simple logic does not hold — that a person sensitive to bitterness will necessarily avoid coffee.
Sources for this overview
Checked for this overview: Quantitative chemistry and sensory research treating roasting byproducts and extraction conditions / Research showing that roasting conditions and water extraction alter bitter-compound concentrations
Contribution of mozambioside roasting products to coffee's bitter taste
Checked for this overview: Research on the bitterness contribution of mozambioside roasting byproducts
Checked for this overview: A review article organizing the fact that caffeine cannot serve as a universal representative of bitterness
Bitterness compounds in coffee brew measured by analytical instruments and taste sensing system
Checked for this overview: Methodological limitations of candidate identification by electronic taste sensor and statistical model
Checked for this overview: A trial with 155 subjects comparing taste-sensitivity immediately after normal and decaffeinated coffee consumption
Checked for this overview: Negative association between quinine and PROP bitterness sensitivity and coffee intake / Result showing that the direction of the relationship between caffeine bitterness sensitivity and intake reverses
Follow the connections
coffee brew →shows the sensory response→ bitterness →can be measured separately …→ astringency
coffee brew →has bitter contributors oth…→ caffeine →is a poor universal prototy…→ bitterness
chlorogenic acid →has a measured content in→ coffee brew
coffee brew →— perceived bitterness is s…→ sweetness →can reduce the perceived bi…→ bitterness
Structured claims — open a section to read each claim's confidence, evidence and limits
Composition and content (5)
Scope: 4 stages of roast level evaluated by instrumental chemical analysis and electronic taste sensor
Note: Candidate ranking was by PLS-R and taste sensor, not by human sensory panel.
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ingredient-coffee-brew —has_candidate_bitterness_contributors→ "Nicotinic acid, L-lactic acid, and nicotinamide in the research fraction"Scope: Multiple lines of evidence: human sensory testing, receptor assays, and quantitative chemistry
Note: A group of counterexamples to the common belief that 「コーヒーの苦味＝カフェイン」 (in translation: "coffee's bitterness equals caffeine"). The quantitative contribution ratio is not recorded, since the full text was not confirmed.
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ingredient-coffee-brew —has_bitter_contributors_other_than→ compound-caffeineScope: Quantification by UV-Vis spectrophotometry (330 and 272 nm, 70% ethanol extraction), compared against a standard calibration curve
Note: หนองน้ำดำ (Nong Nam Dam) village is not necessarily the same growing area as Doi Tung/Doi Chang, but it connects to this cluster in the context of arabica grown under a Royal Project in northern Thailand. Only the abstract was checked (the full-text PDF was rasterized and could not be extracted).
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compound-chlorogenic-acid —has_measured_content_in→ ingredient-coffee-brewScope: Connection of the GI-standard product classification (including green beans, roasted beans, and ground coffee) to the existing ingredient-coffee-brew entry, a beverage extracted from roasted beans, as a geographically restricted version of that entry
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ingredient-doi-tung-coffee —is_associated_with→ ingredient-coffee-brewNote: Connects to the existing entry ingredient-coffee-brew.
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ingredient-kopi —is_a_type_of→ ingredient-coffee-brewSensory (9)
Scope: Electronic taste-sensor response to fractionated coffee extract
Note: The cited experiment does not provide confirmation by human sensory evaluation.
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ingredient-coffee-brew —has_sensory_response→ sensation-bitterScope: Mendelian randomization in UK Biobank (n = 438,870, white British ancestry)
Note: This holds for quinine and PROP bitterness (-0.081 / -0.021 cups/day per SD), but reverses for caffeine bitterness, in which higher intake increases. Because the direction differs by substance, the rule 『苦味感受性が高いほど苦味飲料を避ける』 (in translation: "the higher the bitterness sensitivity, the more one avoids bitter beverages") cannot be treated as general.
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ingredient-coffee-brew —has_consumption_reduced_by→ "Genetically high bitterness perception (the classical bitterness aversion model)"Scope: Taste and smell sensitivity testing before and after coffee intake in 155 people
Note: Smell sensitivity did not change, and the effect was reproduced with decaf, so it cannot be attributed to caffeine alone. A short-term effect.
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ingredient-coffee-brew —can_remain_changed_after→ "Immediately after intake, sweetness sensitivity rose and bitterness sensitivity fell. The same was true for both regular coffee and decaf"Scope: Layer: food. A human psychophysical test of mixtures of brewed coffee and sucrose (abstract only; concentration and number of participants not confirmed).
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ingredient-coffee-brew —has_perceived_bitterness_suppressed_by→ sensation-sweetScope: Layer: food. Full-immersion-brewed coffee (light roast and dark roast) was brewed at 4°C, 22°C, and 92°C, and a trained panel of 14 (10 women, 4 men) evaluated 27 attributes. Bitterness, sourness (sour), burnt, smoky, and rubber notes all increased together with rising total dissolved solids (TDS), and for dark roast these attributes increased significantly with rising brew temperature (Liang, Batali, Ristenpart & Guinard 2024).
Note: An example where bitterness and sourness do not suppress each other, but move in the same direction depending on brew strength. Placed here as an example of co-variation rather than mutual suppression between sourness and bitterness.
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ingredient-coffee-brew —has_perceived_bitterness_affected_by→ "Brew temperature (for dark roast, raising it 4°C → 22°C → 92°C significantly increased bitterness) and total dissolved solids. Sourness was also higher at 92°C; bitterness and sourness did not cancel each other out but moved in the same direction"Scope: Layer: food. Drip-brewed coffee. This is a comparison under conditions where brew strength and percent extraction were experimentally controlled, so it may not generalize directly to home brewing, where raising the water temperature also tends to move the concentration. A descriptive sensory analysis of 31 attributes by a trained panel of 12 (8 women, 4 men, ages 19-30).
Note: A counterexample to the naive expectation that “changing the water temperature changes the bitterness.” Note that this is conditional on TDS being held constant.
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ingredient-coffee-brew —has_perceived_bitterness_unchanged_by→ "Under conditions where brew strength (TDS) and percent extraction (PE) were fixed at target values, varying the brew water temperature across 87°C, 90°C, and 93°C showed no statistically significant difference in the trained panel's bitterness score (the effect of brew temperature was p=0.11 in multivariate analysis). Attributes including bitterness changed together with TDS, but did not correlate with brew temperature itself."Scope: Layer: food. Sensory evaluation on a 5-point scale, 0 (not detectable) to 5 (strongly detected), by 18 panelists (8 women, 10 men, ages 23-31). Caffeine was added to a decaffeinated roasted coffee beverage (a commercial capsule, equivalent to 54 g/L).
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ingredient-coffee-brew —has_perceived_bitterness_unchanged_by→ compound-caffeineScope: Layer: Food. QDA by a trained panel of 18 and consumer preference survey of 120. Traditional and decaffeinated espresso sweetened with sucrose, sucralose, or stevia (multiple rebaudioside A concentrations) were compared.
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ingredient-coffee-brew —has_perceived_bitterness_affected_by→ compound-caffeineScope: Layer: food. An experiment contaminating natural-processed specialty coffee with quaker beans (from immature beans), with sensory evaluation and volatile compound analysis. The number and training status of the sensory panel are not stated in the abstract.
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ingredient-coffee-brew —has_perceived_bitterness_affected_by→ "In a sensory evaluation adding quaker beans (from immature beans, in 3 color grades) to natural-processed specialty coffee at 7 levels of contamination, quaker beans increased bitterness and astringency and brought negative sensory descriptors to aroma and flavor. For quaker beans with an Agtron color of 82.8 or above, a significant sensory difference appeared only once contamination reached 7 beans (10.8%) or more in 1 cup (equivalent to 65 beans)."How processing and cooking change it (1)
Scope: Vietnam, Cholon district, Saigon (Ho Chi Minh City)
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ingredient-coffee-brew —is_processed_by→ process-vietnamese-butter-roasting