Coffee is know to contain over 1000 chemical compounds that contribute to both the taste and aroma of coffee. Although Caffeine is the most well know molecule and although is a bitter compound, it only contributes about 15% of coffee's bitter compounds. Caffeine does however bind to adenosine receptors in the brain which is causes a stimulant effect.
Phenolic compounds are ubiquitous constituents of higher plants found in a wide range of commonly consumed plant foods including coffee. These compounds are secondary metabolites of plants generally involved in defense against ultraviolet radiation, and as natural animal toxicants and pesticides against invading organisms.
While condensed tannins are the main phenolic compounds in coffee pulp, in the seed, phenolic compounds are present predominantly as a family of esters formed between certain hydroxycinnamic acids and quinic acid, collectively known as chlorogenic acids (CGA). CGA, which are present in high concentrations in green coffee seeds (up to 14 %), have a marked influence in determining coffee quality and play an important role in the formation of coffee flavor. See the abstract below and full review article for more details on this topic.
From: Phenolic compounds in coffee - Brazilian Journal of Plant Physiology - Adriana Farah; Carmen Marino Donangelo
Abstract: "Phenolic compounds are secondary metabolites generally involved in plant adaptation to environmental stress conditions. Chlorogenic acids (CGA) and related compounds are the main components of the phenolic fraction of green coffee beans, reaching levels up to 14 % (dry matter basis). These compounds have a number of beneficial health properties related to their potent antioxidant activity as well as hepatoprotective, hypoglycemic and antiviral activities. The main groups of CGA found in green coffee beans include caffeoylquinic acids, dicaffeoylquinic acids, feruloylquinic acids, p-coumaroylquinic acids and mixed diesters of caffeic and ferulic acids with quinic acid, each group with at least three isomers. During coffee processing, CGA may be isomerized, hydrolyzed or degraded into low molecular weight compounds. The high temperatures of roasting also produce transformation of part of CGA into quinolactones and, along with other compounds, melanoidins. This review focuses on the chemical characteristics, biosynthesis, and distribution of CGA and related compounds in coffee. The influence of genetic, physiological and environmental factors as well as processing on the chemical composition of coffee beans is discussed. The impact of CGA composition of green coffee on cup quality is also approached. Despite the existence of substantial published information on the total levels of CGA in coffee, more research is needed on the composition of minor phenolic compounds and specific CGA isomers (and related substances) in green and roasted coffee beans, as well as their impact on coffee quality." Full Review article available online
In a research study done by Thomas Hofmann, Ph.D., a professor of food chemistry and molecular sensory science at the Technical University of Munich in Germany.-- the main source of bitterness is from two sources: chlorogenic acid lactons and pheylindanes. Both the lactones as well as the phenylindanes are derived from chlorogenic acid, which is not itself bitter. Chlorogenic acid is found in the green unroasted coffee bean.
According to Hoffman, roasting is the key factor driving the bitter taste in coffee beans. So the stronger you roast the coffee, the more harsh itwill tends to get. We've known for some time that the chlorogenic acid lactones are present in coffee, but their role as a source of bitterness was not known until now," Hofmann says. Ironically, the lactones as well as the phenylindanes are derived from chlorogenic acid, which is not itself bitter.
Screening and identification of bitter compounds in roasted coffee brew by taste dilution analysis -Developments in Food Science- Oliver Franka, Gerhard Zehentbauerb, Thomas Hofmann (2007)
Abstract: Intense bitter taste compounds were identified in roasted coffee brew using sensory-guided fractionation, LC-MS/MS and 1D/2D-NMR spectroscopy, syntheses, and model roasting experiments with potential precursors. The intense bitter tastants of coffee were 3-O-caffeoyl-γ-quinide (1), 4-O-caffeoyl-γ-quinide (2), 4-O-caffeoyl-muco-γ-quinide (3), 5-O-caffeoyl-muco-γ-quinide (4), 5-O-caffeoyl-epi-δ-quinide (5), 3-O-feruloyl-γ-quinide (6), 4-O-feruloyl-γ-quinide (7) 3,4-O-dicaffeoyl-γ-quinide (8), 4,5-O-dicaffeoyl-muco-γ-quinide (9) and 3,5-O-dicaffeoyl-epi-δ-quinide (10). Determination of the bitter taste recognition thresholds showed that, depending on their chemical structure, the bitter threshold concentrations ranged between 9.8 and 180 μmol/l (water). Quantification and determination of the dose over threshold factors for the individual bitter compounds revealed that approximately 80% of the bitterness of the decaffeinated coffee beverage could be related to these 10 quinides.
Phenylindanes, which are the chemical breakdown products of chlorogenic acid lactones, are found at higher levels in dark roasted coffee, including espresso. These chemicals exhibit a more lingering, harsh taste than their precursors, which helps explain why dark-roasted coffees are generally more bitter, Hofmann says.
Using advanced chromatography techniques and a human sensory panel trained to detect coffee bitterness, Hofmann and his associates found that coffee bitterness is due to two main classes of compounds: chlorogenic acid lactones and phenylindanes, both of which are antioxidants found in roasted coffee beans. The compounds are not present in green (raw) beans, the researchers note.
The lactones derive from chlorogenic acids, also referred to as O-caffeoylquinic acids, which are the predominant polyphenols present in raw coffee beans. Bean roasting either can break these phenolic acids down to form di- and trihydroxybenzenes such as hydroxyhydroquinone or can epimerize and dehydrate the acids to give various lactones that provide a "pleasant, coffeelike bitter taste quality" in light- to medium-roast coffee, Hofmann said.
Thomas Hofmann and his research associate Oliver Frank of Germany's University of Münster turned to fractionation experiments to try to isolate the bitter factors. They found that two groups of components were significant contributors to bitterness: chlorogenic acid lactones and multiply hydroxylated phenylindanes. The lactones derive from chlorogenic acids, also referred to as O-caffeoylquinic acids, which are the predominant polyphenols present in raw coffee beans. Bean roasting either can break these phenolic acids down to form di- and trihydroxybenzenes such as hydroxyhydroquinone or can epimerize and dehydrate the acids to give various lactones that provide a "pleasant, coffeelike bitter taste quality" in light- to medium-roast coffee, Hofmann said.
What is chlorogenic acid? Chlorogenic acid is a natural chemical compound which is the ester of the phenolic acids caffeic acid and (−)-quinic acid.
Chlorogenic Acid Structure
Of all plant constituents, coffee has one of the highest concentrations of chlorogenic acids. Whenroasting coffee, some of these are transformed into chlorogenic acid lactones (CGL). Note: the term chlorogenic acids can also refer to a related family of esters of hydroxycinnamic acids (caffeic acid, ferulic acid and p-coumaric acid) with quinic acid. Green coffee beans contain the largest amounts of CGA foundin plants, ranging from 6 to 12%
Chlorogenic acid lactones, which include about 10 different chemicals in coffee, are the dominant source of bitterness in light to medium roast brews. 5 - caffeoylquinic acid is the most prevalemt of the chlorgenic acids in green coffee beans
According to Adriana Farah, Vanderbilt Institute for Coffee Studies, Vanderbilt University School of Medicine--"Of all plant constituents, coffee has one of the highest concentrations of chlorogenic acids. When roasting coffee, some of these are transformed into chlorogenic acid lactones (CGL). We have studied the formation of CGL during the roasting of coffee beans..." see:
Seven Chlorogenic Acid Lactones were identified: 3-caffeoylquinic-1,5-lactone (3-CQL), 4- caffeoylquinic-1,5-lactone (4-CQL), 3-coumaroylquinic-1,5-lactone (3-pCoQL), 4-coumaroylquinic-1,5-lactone (4-pCoQL), 3-feruloylquinic-1,5-lactone (3-FQL), 4-feruloylquinic-1,5-lactone (4-FQL), and 3,4-dicaffeoylquinic-1,5-lactone (3,4-diCQL). 3-CQL was the most abundant lactone in C. arabica and C. canephora, reaching peak values of 230 ± 9 and 254 ± 4 mg/100 g (dry weight),
Formation of a 1,5- γ -quinolactone from chlorogenic acid during roasting (A), and the two major chlorogenic acid lactones in roasted coffee: 3-caffeoylquinic-1,5- γ -lactone (left) and 4-caffeoylquinic-1,5- γ -lactone (right) (B) Although under IUPAC rules the numbering system for the lactones is different from that for the acids, in order to avoid confusion, most reports in the literature (including the present work) have been using for lactones the same numbering of the carbons as for the acid precursors. Image from: Phenolic compounds in coffee - Brazilian Journal of Plant Physiology - Adriana Farah; Carmen Marino Donangelo.
Green coffee beans actually contain up to 7 percent of chlorogenic acid. Regular coffee beans lose some of the amount they contain after the beans have been roasted.
During roasting, CGA's slowly decompose to form caffeic and quinic acid with about 50% of the original CGA being destroyed in a medium roast.
According to Thomas Hoffman there are a thousand volatile compounds that have been identified in coffee, though just 40 or so of these substances "have been demonstrated to contribute to the alluring smell". They include β-damascenone (which has an aroma like cooked apples), 2-furfurylthiol (sulfury, roasty), 2-isobutyl-3-methoxypyrazine (earthy), guaiacol (spicy), 2,3-butanedione (buttery), and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (caramel-like). The flavor and aroma compounds derive from multiple chemical reactions, including the Maillard reaction, caramelization, polyphenol degradation, polymerization of carbohydrates, and pyrolysis. see: Tweaking Coffee's Flavor Chemistry --Chemical and Engineering News.
Phenylindanes, which are the chemical breakdown products of chlorogenic acid lactones, are found at higher levels in dark roasted coffee, including espresso. These chemicals exhibit a more lingering, harsh taste than their precursors, which helps explain why dark-roasted coffees are generally more bitter according to Thomas Hofmann.
The type of brewing method used can also influence the perception of bitterness. Espresso-type coffee, which is made using high pressure combined with high temperatures, tends to produce the highest levels of bitter compounds. While home-brewed coffee and standard coffee shop brews are relatively similar in their preparation methods, their perceived bitterness can vary considerably depending on the roasting degree of the beans, the amount of coffee used, and the variety of beans used.
Although some reports are as high as 28%--(Roasted coffee beans are ~28% (by weight) water-soluble. This means that you can extract ~28% of the coffee bean's mass in water. The rest is pretty much cellulose and plant stuff that forms the structure of the seed.
Yields of under 18% are "under-extracted", specifically "under-developed" – desirable components have not been sufficiently extracted – and "unbalanced", specifically sour, because acids are extracted early, while balancing sugars (sweetness) and bitter components are extracted later.
Yields of over 22% are "over-extracted", specifically bitter, as bitter components continue to be extracted after acids and sugars have largely completed extraction. In certain situations, yields surpassing 22% can be absent of bitterness.
Caffeine is extracted early, so higher yields do not yield more caffeinated coffee, only over-extracted coffee.
Tweeking Coffees Flavor Chemistry - American Chemical Society
Coffee Chemistry - Chlorogenic Acid
Coffee Chemistry: Coffee Aroma
Phenolic compounds in coffee - Brazilian Journal of Plant Physiology - Adriana Farah; Carmen Marino Donangelo
The Chemistry of Coffee - Why is Coffee Bitter - Compoundchem.com
Science of Chocolate
Kahawa ina zaidi ya kemikali 1000 ambazo huchangia ladha na harufu ya kahawa. Caffeine ni molekuli ya uchungu, ambayo inahusika katika asilimia 15 tu ya uchungu wa kahawa. Hata hivyo, kafeini huunganishwa na vipokezi vya adenosini katika ubongo ambavyo husababisha athari ya kuchochea. Phenols ni sehemu ya mimea ya juu ambayo hupatikana katika aina mbalimbali za vyakula vya mimea vinavyotumiwa kwa kawaida, ikiwa ni pamoja na kahawa. Vifaa hivi ni metabolites za sekondari za mimea kwa ujumla kushiriki katika ulinzi dhidi ya mionzi ya ultraviolet, na kama sumu ya asili ya wanyama na dawa za kuua wadudu dhidi ya viumbe wanaovamia. Tannins ni kemikali ya msingi ya phenolic katika nyanya ya kahawa, lakini katika mbegu, phenolic huwepo hasa kama familia ya esters iliyoundwa kati ya asidi fulani ya hydroxycinnamic na asidi quinic, pamoja inayojulikana kama asidi chlorogenic. CGA, ambayo inapatikana katika viwango vya juu katika mbegu za kahawa ya kijani (hadi 14%), ina ushawishi mkubwa katika kuamua ubora wa kahawa na ina jukumu muhimu katika kuunda ladha ya kahawa. Angalia muhtasari hapa chini na makala kamili ya ukaguzi kwa maelezo zaidi juu ya mada hii. "Kutokana na utafiti uliofanywa na jarida la Brazilian Journal of Plant Physiology, Adriana Farah, na Carmen Marino Donangelo, ""Mchanganyiko wa phenolic ni metabolites ya sekondari ambayo kwa ujumla inahusika katika marekebisho ya mimea kwa hali ya shinikizo la mazingira.""" Chlorogenic asidi (CGA) na misombo inayohusiana ni sehemu kuu ya sehemu ya phenolic ya maharagwe ya kahawa ya kijani, kufikia viwango vya hadi 14%. Vifaa hivi vina sifa kadhaa za afya zinazohusiana na shughuli zao za nguvu za antioxidant na pia hepatoprotective, hypoglycemic na antiviral. Asidi za CGA zinazopatikana katika maharagwe ya kahawa ya kijani ni pamoja na asidi za caffeoylquinic, asidi za dicaffeoylquinic, asidi za ferulokinic, asidi za p-coumaroylquinic, na diesters mchanganyiko wa asidi za caffeic na ferulic na asidi ya quinic, kila kundi na isomers tatu. Wakati wa usindikaji wa kahawa, CGA inaweza kuwa isomerized, hydrolyzed au degraded katika misombo ya uzito wa molekuli ya chini. Kwa sababu ya joto la juu, sehemu ya CGA inageuka kuwa quinolactone na pamoja na misombo mingine, melanoidine. Utafiti huu unazingatia sifa za kemikali, biosynthesis, na usambazaji wa CGA na misombo inayohusiana katika kahawa. Uvutano wa vimeng'enya, kisaikolojia na mazingira pamoja na usindikaji juu ya muundo wa kemikali ya maharagwe ya kahawa ni kujadiliwa. Mfano wa CGA ya kahawa ya kijani ni muhimu kwa ubora wa kikombe. "Licha ya kuwepo kwa habari kubwa iliyochapishwa juu ya viwango vya jumla vya CGA katika kahawa, utafiti zaidi unahitajika juu ya muundo wa misombo ndogo ya phenolic na isomers maalum ya CGA katika maharagwe ya kahawa ya kijani na ya kuchomwa, na vile vile athari zao kwa ubora wa kahawa. """ Katika utafiti uliofanywa na Thomas Hofmann, Ph.D., profesa wa kemia ya chakula na sayansi ya molekuli ya hisia katika Chuo Kikuu cha Ufundi cha Munich nchini Ujerumani, chanzo kikuu cha uchungu ni kutoka vyanzo viwili: lactons ya asidi chlorogenic na phenylalanine. Laktoni na phenylindanes hutokana na asidi ya chlorogenic, ambayo yenyewe si kali. Asidi ya klorogeni hupatikana katika maharagwe ya kahawa ya kijani yasiyochomwa. Kulingana na Hoffman, kuchoma kahawa ndiyo sababu kuu inayofanya kahawa iwe na ladha kali. Kwa hiyo, kadiri unavyochoma kahawa kwa nguvu zaidi, ndivyo inavyokuwa kali zaidi. """Tumejua kwa muda kwamba lactones ya asidi chlorogenic zipo katika kahawa, lakini jukumu lao kama chanzo cha uchungu halikujulikana hadi sasa,"" anasema Hofmann." Kwa kushangaza, lactones na vilevile phenylindanes hutokana na asidi ya chlorogenic, ambayo yenyewe si kali. Utafiti wa uchungu wa kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa. Kwa mfano, katika majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio ya majaribio. Kwa mujibu wa utafiti wa kihistoria, kiwango cha uchungu wa ladha ya uchungu ni kati ya 9.8 na 180 mmol l (maji). Kwa mfano, kwa sababu ya viwango vya juu vya kiini, kiasi cha uchungu wa kahawa ya decaffeinated inaweza kuwa karibu 80% ya uchungu wa kahawa ya decaffeinated. Phenylindane ni kemikali ya kutenganisha ya lactones ya asidi chlorogenic, ambayo hupatikana katika viwango vya juu katika kahawa ya kahawa ya kahawa, pamoja na espresso. "Kemikali hizi zina ladha kali zaidi kuliko zile za awali, ambayo husaidia kuelezea kwa nini kahawa zilizokaangwa kwa giza kwa ujumla ni kali zaidi, ""Hofman anasema." Kwa kutumia mbinu za hali ya juu za chromatography na jopo la hisia za binadamu zilizozoezwa kugundua uchungu wa kahawa, Hofmann na washirika wake walipata kwamba uchungu wa kahawa unatokana na makundi mawili makuu ya misombo: lactones ya asidi chlorogenic na phenylindanes, ambayo ni antioxidants zinazopatikana katika maharagwe ya kahawa. Watafiti hao wanasema kwamba kemikali hizo hazipatikani katika maharagwe ya kijani kibichi. Lactone ni asidi ya chlorogenic, ambayo pia inajulikana kama asidi ya O-caffeine, ambayo ni polyphenols kubwa katika maharagwe ya kahawa. "Kupika maharagwe kunaweza kuvunja asidi hizi za phenolic chini ya kuunda di- na trihydroxybenzenes kama vile hydroxyhydroquinone au epimerize na dehydrate asidi kutoa lactones mbalimbali ambazo hutoa ""ladha nzuri, kahawa kama uchungu"" katika kahawa nyepesi hadi ya kati." Thomas Hofmann na Oliver Frank, mtafiti mwenzake wa Chuo Kikuu cha Münster, Ujerumani, walifanya majaribio ya kugawanya vipande hivyo ili kujaribu kutenganisha vitu hivyo vyenye uchungu. Kwa mfano, kuna makundi mawili ya viungo vya kiungo cha damu vinavyochangia uchungu: chlorogenic acid lactones na phenylalanine. Lactone ni asidi ya chlorogenic, ambayo pia inajulikana kama asidi ya O-caffeine, ambayo ni polyphenols kubwa katika maharagwe ya kahawa. "Kupika maharagwe kunaweza kuvunja asidi hizi za phenolic chini ya kuunda di- na trihydroxybenzenes kama vile hydroxyhydroquinone au epimerize na dehydrate asidi kutoa lactones mbalimbali ambazo hutoa ""ladha nzuri, kahawa kama uchungu"" katika kahawa nyepesi hadi ya kati." Asidi ya klorogeni ni nini? Chlorogenic asidi ni kemikali ya asili ambayo ni ester ya asidi phenolic asidi caffeic na asidi (−) -quinic. Chlorogenic Acid: Katika mimea yote, kahawa ina kiasi kikubwa cha asidi ya chlorogenic. Wakati wa kuchoma kahawa, baadhi ya hizi hubadilishwa kuwa lactones ya asidi ya chlorogenic (CGL). "Hii ni pamoja na ""acid chlorogenic"" ambayo ni pamoja na asidi ya hydroxycinnamic (asidi ya caffeic, asidi ya ferulic, asidi ya p-coumaric) na asidi ya quinic." Mazao ya kahawa ya kijani yana kiasi kikubwa cha CGA-Fundin, kuanzia 6-12% ya asidi ya klorogeni, ambayo ni pamoja na kemikali 10 tofauti katika kahawa, na ni chanzo kikuu cha uchungu katika kahawa nyepesi hadi ya kati. "Kufikia sasa, asidi ya caffeine ya caffeine ni moja ya asidi za ""chlorogenic"" katika maharagwe ya kahawa ya kijani, kulingana na Adriana Farah, Mtaalamu wa Chuo Kikuu cha Vanderbilt, Chuo Kikuu cha Vanderbilt, Chuo Kikuu cha Chuo Kikuu cha Vanderbilt, ""Katika viungo vyote vya mimea, kahawa ina moja ya viwango vya juu zaidi vya asidi ya chlorogenic." Wakati wa kuchoma kahawa, baadhi ya hizo hubadilishwa kuwa lactones za asidi chlorogenic (CGL). "Kama ilivyoelezwa katika makala hii, ""Chlorogenic Acid Lactone"" ni aina ya asidi ya klorogeni inayoweza kutengenezwa kwa kutumia 3-Chlorogeni-1,5-lactone, 4-Chlorogeni-1,5-lactone, 3-Chlorogeni-1,5-lactone, 4-Chlorogeni-1,5-lactone, 4-Chlorogeni-1,5-lactone, 4-Chlorogeni-1,5-lactone, 4-Chlorogeni-1,5-lactone, 4-Chlorogeni-1,5-lactone, 4-Chlorogeni-1,5-lactone, 4-Chlorogeni-1,5-lactone, 4-Chlorogeni-1,5-lactone, 4-Chlorogeni-1,5-lactone, 4-Chlorogeni-1,5-lactone." Lactone ya C2C2 ilikuwa lactone ya kawaida zaidi katika C. arabica na C. canephora, ikifikia viwango vya juu vya 230 ± 9 na 254 ± 4 mg g (uzito kavu), na pia ilikuwa lactone ya msingi katika kahawa iliyokaushwa, 3-caffeine-lactone na 4-caffeine-lactone. Picha kutoka: Phenolic misombo katika kahawa - Brazilian Journal ya Mimea Physiology - Adriana Farah; Carmen Marino Donangelo. Kwa mfano, maharagwe ya kahawa ya kijani yana asilimia 7 ya asidi ya klorogeni. Mbegu za kahawa za kawaida hupoteza kiasi fulani cha kiasi kilicho ndani yake baada ya mbegu hizo kuchomwa. Wakati wa kuchoma, CGA hufinyangwa polepole na kuunda asidi ya caffeic na quinic, na karibu 50% ya CGA ya awali kuharibiwa katika kuchoma kwa wastani. Kulingana na Thomas Hoffman, kuna kemikali elfu moja ambazo zimepatikana katika kahawa, ingawa ni 40 tu kati ya hizo ambazo "zimethibitishwa kuwa na harufu nzuri". Vipengele vya B-Damascene (ambayo ina harufu kama ya apples cooked), 2-furfurylthiol (sulfuric, roasted), 2-isobutyl-3-methylpyrazine (earthy), guava (spicy), 2-butandione (buttery), na 4-hydroxy-2-dimethyl-3-methyl-2-furanone (caramel-like). Ladha na harufu misombo hutokana na athari nyingi za kemikali, ikiwa ni pamoja na athari ya Maillard, caramelization, uharibifu wa polyphenol, polymerization ya wanga, na pyrolysis. Angalia: Tweaking Coffee's Flavor Chemistry --Chemical na Uhandisi Habari. Phenylindane ni kemikali ya kutenganisha ya lactones ya asidi chlorogenic, ambayo hupatikana katika viwango vya juu katika kahawa ya kahawa ya kahawa, pamoja na espresso. "Kama vile, ""kahawa ya rangi ya kijivu"" ina ladha kali zaidi kuliko kahawa ya rangi ya kijivu, ambayo inasaidia kuelezea kwa nini kahawa ya rangi ya kijivu kwa ujumla ni kali zaidi kulingana na Thomas Hofmann." Aina ya njia ya kutengeneza bia inayotumiwa pia yaweza kuathiri jinsi uchungu unavyoonekana. Kahawa ya espresso, ambayo hutengenezwa kwa kutumia shinikizo la juu pamoja na joto la juu, huwa na viwango vya juu zaidi vya misombo ya uchungu. Wakati kahawa ya nyumbani na kahawa ya kawaida ya duka la kahawa ni sawa katika njia zao za maandalizi, uchungu wao unaotambuliwa unaweza kutofautiana sana kulingana na kiwango cha kuchoma cha maharagwe, kiasi cha kahawa inayotumiwa, na aina ya maharagwe. Kwa mfano, katika nchi za Ulaya, kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa ya kahawa. Hii inamaanisha kwamba unaweza kutoa karibu 28% ya wingi wa maharagwe ya kahawa katika maji. Sehemu ya pili ni cellulose na nyenzo za mimea ambazo huunda muundo wa mbegu. Matokeo ya chini ya 18% ni "under-kuondolewa", hasa "under-kuendelea" <unk> vipengele vya kutamaniwa havijaondolewa vya kutosha <unk> na "unbalanced", hasa sour, kwa sababu asidi ni extracted mapema, wakati kusawazisha sukari (sweetness) na vipengele uchungu ni extracted baadaye. Kwa sababu ya matokeo ya juu ya 22% ni "over-extracted", hasa uchungu, kama vipengele uchungu kuendelea kuchimbwa baada ya asidi na sukari kwa kiasi kikubwa kukamilika uchimbaji. Katika hali fulani, mavuno ya zaidi ya 22% yanaweza kuwa bila uchungu. Caffeine hutolewa mapema, kwa hiyo mavuno ya juu hayatokezi kahawa zaidi ya caffeinated, kahawa tu iliyotokezwa kupita kiasi. "Kichwa cha habari cha ""Kichwa cha Kahawa"" ni ""Kichwa cha Kahawa"" na ""Kichwa cha Kahawa"" ni ""Kichwa cha Kahawa"" na ""Kichwa cha Kahawa"" ni ""Kichwa cha Kahawa"" na ""Kichwa cha Kahawa"" ni ""Kichwa cha Kahawa"" na ""Kichwa cha Kahawa"" ni ""Kichwa cha Kahawa"" na ""Kichwa cha Kahawa"" ni ""Kichwa cha Kahawa."""