Influence of coffee/water ratio on the final quality of espresso coffee

Espresso coffee is a polyphasic beverage in which the physico‐chemical and sensory characteristics obviously depend on both the selection of ground roasted coffee and the technical conditions of the percolation process. The aim of this work was to evaluate the influence of the coffee/water ratio on the physico‐chemical and sensory quality of espresso coffee. Furthermore, the influence of botanical varieties (Arabica and Robusta) and the type of roast (conventional and torrefacto) on the selection of coffee/water ratio was studied. The relationship between pH and the perception of acidity intensity is discussed in relation to the influence of the coffee/water ratio, type of coffee and roast. The optimisation of other technical parameters in previous studies seemed to minimise the influence of an increase in the coffee/water ratio on the extraction of soluble and solid compounds. In fact, only some sensory attributes, such as bitterness, astringency and burnt, acrid and earthy/musty flavours were proposed as relevant to the selection of 6.5 g 40 mL^?1 or 7.5 g 40 mL^?1 in conventional roasted coffees (Arabica 100% and Robusta blend), and 6.5 g 40 mL^?1 in torrefacto roasted coffees. On the other hand, the addition of sugar during the roasting process in torrefacto roast coffees seemed to contribute to a higher generation of acids, melanoidins and other compounds by the Maillard reaction or caramelisation, which led us to select the lowest coffee/water ratio. Copyright © 2006 Society of Chemical Industry     

Influence of torrefacto roast on antioxidant and pro-oxidant activity of coffee

The addition of sugar at the end of the torrefacto roasting process may influence the antioxidant and pro-oxidant properties of coffee because sugar is one of the main precursors the Maillard reaction. The aim of the work was to study and to compare the antioxidant and pro-oxidant properties of some commercial roasted coffees which are selected to represent conventional roasted arabica coffee and arabica/robusta blends, and torrefacto roasted blends. Higher antioxidant activity was observed in Colombian coffees than in conventional roasted coffee blends. On the other hand, when the percentage of torrefacto coffee was increased, an increase of the antioxidant activity and a slight tendency to decrease the pro-oxidant activity were observed. Moreover, principal component analysis allowed separation of: (a) brands by PC1 (46.9%), characterised by colour parameters defined by roasting degree and (b) torrefacto roasted blends by PC2 (33.7%), characterised by antioxidant/pro-oxidant activity.     

Difructose anhydrides as quality markers of honey and coffee

Difructose anhydrides (DFAs) are pseudodisaccharides produced by condensation of two fructose molecules by means of caramelization reaction which takes place during heating of sugars or sugar-rich foodstuffs. The aim of this research was to evaluate the feasibility of DFAs as chemical markers of honey authenticity and sugar-roasted torrefacto coffee. DFAs were analysed by gas chromatography coupled to mass spectrometry after conversion to their trimethylsilyl (TMS) derivatives. α-d-fructofuranoside-1,2′:2,1′-α-d-fructofuranoside (DFA7) and α-d-fructofuranoside-1,2′:2,1′-β-d-fructopyranoside (DFA9) can be used as quality markers of honey and coffee. DFA7 and DFA9 were detected in honey added with 5% fructose and sucrose caramels and 15% of glucose caramels. Torrefacto coffees showed DFAs values ranged from 0.195 to 0.570 g/100 g whereas only traces were found in natural roasted coffees. Quantities from 0.073 to 0.189 g/100 g were measured in blends of natural and torrefacto roasted coffees. A relationship between DFAs content in torrefacto coffees and roasting conditions was observed. In conclusion, this study indicated that DFAs are useful chemical indicators to control honey authenticity and torrefacto coffee roasting.     

Comparison of antioxidant and pro-oxidant activity in coffee beverages prepared with conventional and “Torrefacto” coffee

Antioxidant and pro-oxidant properties of coffee can be affected by several factors such as coffee variety, roasting process, storage, etc. The aim of this study was to compare the antioxidant and pro-oxidant properties of coffee beverages obtained with conventional and torrefacto roasted coffee.Coffee variety influences on the antioxidant capacity of ground coffee. A100 roasted samples presented lower antioxidant capacity than Robusta varieties. This could be due to the higher percentage of chlorogenic acids in Robusta ground coffee than in Arabica. Beside, A100 samples presented the highest value of pro-oxidant activity because these samples presented less efficient antioxidants.In Torrefacto roast, the antioxidant capacity increased and redox potential decreased due to the formation of MRPs, which have reducing properties.     

Comparative study of polyphenols and caffeine in different coffee varieties affected by the degree of roasting

The bioactive composition of coffee, as one of the most popular beverages in the world, has attracted interest as a potential source of beneficial bioactive compounds, especially polyphenols and caffeine. Since the content of these compounds is affected by the processing conditions, the objective of this study was to determine the content of polyphenolic compounds and caffeine in four different coffee varieties: Minas and Cioccolatato (Coffea arabica), and Cherry and Vietnam (Coffea canephora syn. Coffea robusta), roasted by three varying degrees (light, medium and dark). The content of the polyphenolic compounds and the antioxidant capacity of coffees were determined using UV/Vis spectrophotometric methods, while the content of chlorogenic acid derivatives was determined using HPLC analysis. The caffeine content was determined by means of two spectrophotometric methods, as well as HPLC analysis. Additionally, raw caffeine was also obtained by an isolation procedure with chloroform. Cherry coffee, a variety of C. canephora exhibited the highest overall content of total phenols (42.37 mg GAE/g), followed by Minas coffee, while Cioccolatato contained the lowest TPC (33.12 mg GAE/g). Cherry coffee also exhibited the highest content of individual classes of polyphenols (flavan-3-ols, procyanidins and tannins), while the highest content of chlorogenic acid (CQA) derivatives was determined in Minas and Cioccolatato coffees (C. arabica). The highest content of total and individual polyphenolic compounds was determined in coffees roasted in both light and medium roasting conditions, which was also observed for the content of CQA derivatives and antioxidant capacity of roasted coffees. The highest caffeine content in the coffee samples was determined by employing the HPLC analysis (0.06–2.55%). Light roasted Cherry coffee contained the highest overall content of caffeine among all coffees, which exhibited a decrease with intensified roasting.     

ABTS radical scavenging capacity in green and roasted coffee extracts

The impact of two parameters (temperature and duration) on the radical scavenging capacity of individual compounds, and total extracts found in coffee was investigated. Phenolic coffee extracts of light (200 °C), medium (225 °C) and dark (235 °C) roasted coffees in a range of 0–30 min were analyzed by an on-line RP-HLPC-ABTS^•+ decolourization assay. This study revealed a general decrease of radical scavenging capacity related to native phenolic compounds. Processing coffee beans leads to generation of up to 10 new radical scavengers. The roasting process influences not only color and taste in coffees, but also the radical scavenging capacity of coffee as well. Phenolic content in roasted coffee and green coffee is very different. Six compounds identified as caffeoylquinic acids and dicaffeoylquinic acids, endowed with radical scavenging capacity were found in green coffee, whereas depending on the roasting process, roasted coffees can present up to 16 different radical scavengers. The compounds formed during the roast are most likely chlorogenic acids derivatives, of which 4 could be clearly identified as two feruloylquinic acids and two caffeoylquinides. In longer roasting durations, these molecules are subjected to auto-degradation, thus total radical scavenging capacity in coffee decline along with roasting (duration and temperature).     

Antioxidant activity of coffee brews

The total antioxidant activity of coffee beverages was measured with stabilized radical EPR spectroscopy. Depending on which stabilized radical is used, Fremy's salt (potassium nitrosodisulphonate) or 2,2,6,6-tetramethyl-1-piperidin-1-oxyl (TEMPO) values can differ significantly. For the determination of antioxidant activity of Maillard reaction products in coffee, TEMPO appears to be the better radical marker. Thus the contribution of both main antioxidant active compounds (polyphenols, melanoidins) whose ratio varies with roasting conditions could be estimated. During storage experiments of coffees brews changes in antioxidant action are found to be time dependent. The content of chlorogenic acids increased significantly at higher storage temperatures, probably caused by a release from polymer structures. Additional antioxidant capacity of coffee melanoidins seems to be strongly influenced by atmospheric oxygen. The higher roasted sample is less vulnerable than medium or light roasted coffee. Investigations with model systems showed that among all coffee constituents the carbohydrates are mainly responsible for the formation of oxygen scavenging substances.     

Screening and distinction of coffee brews based on headspace solid phase microextraction/gas chromatography/principal component analysis

The volatile profiles of espresso and plunger (cafetière) coffees prepared from (1) an 80:20 (w/w) blend of natural roasted Robusta and Arabica (Robusta Natural blend), (2) a 40:40:20 (w/w/w) blend of Robusta Natural blend, Robusta torrefacto roast (850 g kg^?1 Robusta, 150 g kg^?1 sugar) and (3) natural roasted pure Arabica were established by headspace solid phase microextraction (SPME) after selection of the fibre coating (polyacrylate or polydimethylsiloxane) and the temperature and time of extraction. For the analysis of furans and indoles the polyacrylate coating proved to be more suitable; however, for the overall characterisation of the volatile composition of espresso and plunger coffees the polydimethylsiloxane coating was chosen. SPME/gas chromatography (GC)/mass spectrometry (MS) analyses allowed the identification of 37 compounds: four aldehydes, two ketones, 11 furans, 10 pyrazines, two pyridines, three phenolic compounds, two indoles, one lactone, one ester and one benzothiazine. The volatile composition was related more to the botanical variety (Arabica or Robusta) than to the method of preparation of the brew (espresso or plunger). Furthermore, use of the variability provided solely by the GC peak areas and respective retention times, combined with principal component analysis (PCA), yielded the information necessary for discrimination. The combined technique of headspace SPME/GC/PCA, as an alternative to conventional techniques based on GC/MS, is proposed as a lower‐cost, fast and reliable technique for the screening and distinction of coffee brews. Copyright © 2003 Society of Chemical Industry     

烘焙度对冷萃咖啡理化指标与风味成分的影响

以亚洲咖啡豆为研究对象,分别选取浅、中、深3 种烘焙度的中国云南和印度尼西亚苏门答腊产的卡蒂姆种咖啡豆,比较分析冷萃与热萃方式对萃取浓度、萃取率、可滴定酸、总酚、总糖、咖啡因、葫芦巴碱、绿原酸、抗氧化活性与挥发性成分的差异,并进行主成分分析,从而探究烘焙度对冷萃咖啡理化指标与风味成分的影响规律。结果表明,随着烘焙度增加,冷萃咖啡的萃取浓度、萃取率均显著上升,可滴定酸、总酚、葫芦巴碱、绿原酸、抗氧化活性均显著下降（P＜0.05）。冷萃咖啡较热萃咖啡拥有更高的萃取浓度、萃取率与总糖含量（P＜0.05）,而可滴定酸、总酚含量、抗氧化活性较热萃显著偏低（P＜0.05）。经顶空固相微萃取-气相色谱-质谱检测分析发现,浅烘咖啡豆萃取液中的挥发性成分含量显著低于烘焙度高的咖啡萃取液,深烘咖啡豆萃取液中挥发性成分种类与总含量最多。进一步通过主成分分析能较好区分冷萃和热萃咖啡,两者挥发性成分贡献率具有较大差异。2-丁酮、2-丁烯醛等花香类物质对浅烘冷萃咖啡贡献率更高,而2-甲基吡嗪、糠醇等呈现烘焙坚果类香气物质对浅烘热萃咖啡贡献率更高;2,6-二乙基吡嗪、川芎嗪等烘焙坚果类香气物质对中烘冷萃和热萃咖啡具有较高的贡献率;2-乙烯基呋喃、甲基糠硫醇、2,5-二乙基吡嗪、糠基甲基硫醚等物质对深烘冷萃咖啡有较高贡献率,二甲基二硫、对甲酚、1-甲基吡咯等物质对深烘热萃咖啡贡献率更高。相对于热萃咖啡,烘焙度对冷萃咖啡抗氧化能力与挥发性成分的影响更大。     

Fingerprint and authenticity roasted coffees by <Superscript>1</Superscript>H-NMR: the Brazilian coffee case

With globalization, it has become necessary to adopt policies to regulate the coffee market, addressing problems including the authenticity and traceability of products. It is therefore important to establish methodologies that can help to safeguard the interests of producer countries and add value to products. For this purpose, the use of NMR combined with multivariate statistical procedures can be an attractive option. The aim of this study was to develop a fast and effective technique, using ¹H NMR coupled with multivariate statistics, to create a fingerprint of roasted coffees, distinguishing them according to the main Brazilian producer regions. Several compounds suitable for differentiating roasted coffees were identified in the fingerprint. Discriminant analysis revealed good distinction among the samples. The compounds catechol, trigonelline, caffeine, and n-methylpyridine were most important for the differentiation. The findings should assist coffee-producing countries in adopting measures to protect their markets and to add value to coffee products.     

Discrimination between defective and non-defective Brazilian coffee beans by their volatile profile

The coffee roasted in Brazil is considered to be of low quality, due to the presence of defective coffee beans that depreciate the beverage quality. In view of the fact that coffee flavour is directly related to the volatile compounds produced during roasting, the objective of the present study was to perform a comparative evaluation of the volatile fraction of defective (black, immature, sour) and healthy coffee beans, in order to find possible chemical markers for detection of defective coffee beans in roasted coffee. Volatiles extraction and concentration was performed by solid phase micro-extraction (SPME) of the roasted coffee headspace, using a triple phase (divinylbenzene/carboxen/polydimethylsiloxane) fiber. Analysis of the volatile profiles was performed by GC–MS. The results obtained showed that the proposed methodology was adequate for extraction, concentration and analysis of the coffees volatile profile. Several substances were identified as possible markers for differentiating black, sour and immature beans from healthy coffee beans. Statistical analysis of the data by principal components (PCA) demonstrated that the volatile profile enables the differentiation of healthy and defective coffees. The data were separated into two major groups, one represented by immature and black beans and the other by healthy and sour coffee beans. Such results indicated that black and sour beans can be associated to fermentation of immature and of healthy beans, respectively.     

Occurrence of 3-chloropropane-1,2-diol and its esters in coffee

Fifteen coffee samples comprising green, roasted, decaffeinated and instant coffees were analysed for their content of free and bound 3-chloropropane-1,2-diol (3-MCPD). Green coffees contained only traces of the free 3-MCPD. 3-MCPD in roasted coffees was found at the level of 10.1–18.5 µg/kg. The highest 3-MCPD level of 18.5 µg/kg was found in one instant coffee sample and in coffees with very long time application during roasting. The final colour of the roasted coffee beans was directly linked to the 3-MCPD formed, the darker beans having the greatest concentration, and arabica coffees contained lower 3-MCPD levels than robusta coffees. The level of bound 3-MCPD varied between 6 µg/kg (soluble coffees) and 390 µg/kg (decaffeinated coffee) and exceeded the free 3-MCPD level 8–33 times. Arabica coffees contained higher levels of the bound 3-MCPD than robusta coffees. The recognised precursors of 3-MCPD (salt, glycerol, lipids) were also determined and their influence on the formation of the free and bound 3-MCPD was discussed.     

Usage of Capillary Isotachophoresis and Antioxidant Capacity Measurement in Analysis of Changes in Coffee Properties After Roasting,Steaming and Decaffeination

The aim of the study was to optimise and validate the method for quantitation of short-chained organic acids in coffee brews by capillary isotachophoresis (ITP). The linearity of the method was satisfactory with R ² from 0.9924 for lactic acid to 0.9998 for acetic acid. The limit of detection (LOD) was from 4.9 μmol L^?1 for acetic acid to 24.8 μmol L^?1 for lactic acid. Precision of the method was from 0.20 to 2.69 %. This method was successfully applied to determine six organic acids (tartaric, formic, citric, malic, lactic and quinic) in Arabica and Robusta green and roasted coffee brews. The roasting as well as steaming and decaffeination processes of beans influenced degradation of acids (citric and malic) and their formation (quinic, tartaric, lactic and formic) in coffee brews. The influence of coffee processing on the antioxidant capacity of coffee brews was also tested by using the 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), Folin-Ciocalteu and chelating Fe(II) assays. The roasted coffee brews possessed higher antioxidant capacity than unprocessed coffee brews, excluding chelating activity.     

Correlation between cup quality and chemical attributes of Brazilian coffee

Brazilian arabica coffee is classified for trading according to the quality of the beverage obtained after roasting and brewing. In the present study, Brazilian green and roasted coffee beans were investigated for possible correlations between cup quality and the levels of sucrose, caffeine, trigonelline and chlorogenic acids, determined by HPLC analysis. Trigonelline and 3,4-dicaffeoylquinic acid levels in green and roasted coffee correlated strongly with high quality. To a lesser extent, caffeine levels were also associated with good quality. On the other hand, the amount of defective beans, the levels of caffeoylquinic acids (predominantly 5-caffeoyilquinic acid), feruloylquinic acids, and their oxidation products were associated with poor cup quality and with the Rio-off-flavor. The fact that similar correlations between cup quality and chemical attributes were observed in green and light roasted samples – the latter used for coffee cup classification – indicates that chemical analysis of green beans may be used as an additional tool for coffee quality evaluation.     

Aroma recovery from roasted coffee by wet grinding

Aroma recovery as determined by solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) was compared in coffees resulting from conventional grinding processes, and from wet grinding with cold and hot water. Freshly roasted coffee as well as old, completely degassed coffee was ground in order to estimate the relationship of internal carbon dioxide pressure in freshly roasted coffee with the aroma loss during grinding. The release of volatile aroma substances during grinding was found to be related to the internal carbon dioxide pressure, and wet grinding with cold water was shown to minimize losses of aroma compounds by trapping them in water. Due to the high solubility of roasted coffee in water, the use of wet-grinding equipment is limited to processes where grinding is followed by an extraction step. Combining grinding and extraction by the use of hot water for wet grinding resulted in considerable losses of aroma compounds because of the prolonged heat impact. Therefore, a more promising two-step process involving cold wet grinding and subsequent hot extraction in a closed system was introduced. The yield of aroma compounds in the resulting coffee was substantially higher compared to conventionally ground coffee.     

The influence of brewing method on bioactive compounds residues in spent coffee grounds of different roasting degree and geographical origin

The content of bioactive compounds in spent coffee grounds (SGC) was studied. SGC were obtained from Coffea arabica beans of different roasting degrees (light and dark) and different geographical origins (Nicaragua, Columbia and Mexico) processed using four brewing methods (mocha, filtered, drip and infusion). The highest caffeine and chlorogenic acid contents were determined in filtered spent coffee extracts. All extracts of light roasted spent coffee grounds showed lower browning index levels in comparison to that from dark roasted spent coffee grounds. Generally, the highest content of total polyphenolic compounds and highest antioxidant capacity were determined in extracts prepared in drip. In conclusion, the results obtained in this study indicate that the spent coffee grounds produced of domestic levels, especially those obtained from filter coffeemaker, could be considered as a good source of natural antioxidants.     

Evidence for protective effects of coffees on oxidative stressinduced apoptosis through antioxidant capacity of phenolics

This study evaluated total phenolics, total flavonoids, and antioxidant capacity of randomly selected regular and decaffeinated coffees commercially available in Korea and their protective effects in human hepatic epithelial HepG2 cell line against oxidative stress. All coffees tested exhibited potent antioxidant capacity in chemical systems and, consequently, significant protection of cells from oxidative stress in vitro in a dose-dependent manner. In particular, H₂O₂-induced apoptosis as evaluated by annexin V staining and flow cytometry was prevented by coffee extracts, resulting in the enhanced cell viability. Of interest, the content of total phenolics and flavonoids in coffees demonstrated a positive correlation with antioxidant capacity, indicating that the antioxidant capacity of coffees may be attributed to those phytochemicals. In accordance with previous studies, caffeoylquinic acid (CQA) and its derivatives including 3-CQA, 4-CQA, 5-CQA, 3,4-diCQA, 3,5-diCQA, and 4,5-diCQA were identified as phenolic phytochemicals by a reversed-phase HPLC, with 5-CQA being a major component. Taken together, the present study demonstrated protective effects of regular and decaffeinated coffees on cells in vitro against overwhelming oxidative stress due to richness in phenolics, especially CQA and its derivatives. Coffees, regular or decaffeinated, may serve as a good source of health-beneficial phytochemicals in diet.     

Peroxyl radical-scavenging activity of coffee brews

The ORAC_FL assay was used in non-automated mode to evaluate the specific peroxyl radical scavenging properties of the aqueous soluble components of green and roasted Arabica and Robusta coffee samples. A relationship between ORAC_FL and the concentration of CQAs (caffeoyl quinic acids) was found for the extracts from green coffee beans. Aqueous extracts from roasted coffee beans possessed equal or stronger scavenging power than that obtained for the green coffee beans extracts and the scavenging activity depended on the variety of coffee and the roasting conditions. Brews from Robusta coffee beans showed the highest ORAC_FL. The best scavenging properties for the brews from Arabica coffee beans were detected in samples prepared from coffee beans roasted under light conditions. The data indicate that, during roasting, a complex network of reactions takes place leading to the formation of a wide number of compounds possessing specific scavenging properties. Under mild roasting conditions, caffeoyl quinic acids appear to be the main components responsible for the free radical scavenging power of coffee brews. In contrast, Maillard reaction products may be the principal components with free radical scavenging activity in more severely (medium and dark) roasted coffees.