Chlorogenic acid and caffeine contents in various commercial brewed coffees

Twelve commercial brewed coffees (seven regular and five decaffeinated) were analyzed for chlorogenic acids (CGA) and caffeine by HPLC. Their pH and UV–Vis absorbances were also measured. The CGAs identified were three caffeolylquinic acids (3-CQA, 4-CQA, and 5-CQA), three feruloylquinic acids (3-FQA, 4-FQA, and 5-FQA), and three dicaffeoylquinic acids (3,4-diCQA, 3,5-diCQA, and 4,5-diCQA). The total CGAs ranged from 5.26 mg/g to 17.1 mg/g in regular coffees and from 2.10 mg/g to 16.1 mg/g in decaffeinated coffees. Among CGA, 5-CQA was present at the highest level, ranging from 2.13 mg/g to 7.06 mg/g coffee, and comprising 36–42% and 37–39% of the total CGA in the regular and decaffeinated coffees, respectively. CGA isomer contents were, in decreasing order, 5-CQA > 4-CQA > 3-CQA > 5-FQA > 4-FQA > 3-FQA > 3,4-diCQA > 4,5-diCQA, 3,5-diCQA. The caffeine content in regular and decaffeinated coffees ranged from 10.9 mg/g to 16.5 mg/g and from 0.34 mg/g to 0.47 mg/g, respectively. The pH of regular and decaffeinated coffees ranged from 4.95 to 5.99 and from 5.14 to 5.80, respectively. The relationship between the pH and the UV–Vis absorbance at 325 nm was moderately correlated (R² = 0.7829, p < 0.001, n = 12).     

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).     

Microwave-assisted extraction of chlorogenic acids from green coffee beans

Microwave-assisted extraction (MAE) has been considered as a potential alternative to conventional solvent extraction for the isolation of phenolic compounds from plants. Aqueous and alcoholic extracts of green coffee bean obtained by MAE were quantitatively analysed for total yield of extracts, chlorogenic acids, caffeine and total polyphenol content. The extracts were also evaluated for radical-scavenging activity, using 1,1-diphenyl-β-picrylhydrazyl radical. Under optimum conditions of time (5 min), temperature (50 °C) and wattage (800 W), the maximum chlorogenic acids and caffeine could be extracted with water as solvent. The extracts contained chlorogenic acids and caffeine in the ranges of 31–62% and 22–40%, respectively. The yields of MAE under optimum conditions were higher than those from the conventional solvent extraction at 5 min and 50 °C and the extracts showed radical-scavenging activity of >75%, even at the concentration of 25 ppm. The MAE process can thus be predicted and controlled for industrial application.     

Characterization of Chlorogenic Acids in Coffee by Flow-Through Chronopotentiometry

In this study, flow-through chronopotentiometry (FTCP) has been developed as an electroanalytical method for characterization (identification and quantification) of chlorogenic acids (CGAs) in coffees. The characterization of CGAs in coffee was based on the electrochemical behavior of the main chlorogenic acid (CGAs) isomers presented in coffee (caffeoylquinic acids (CQAs), dicaffeoylquinic acids (diCQAs), and feruloylquinic acids (FQAs)) and the spiking of CGAs standards in coffee samples. The FTCP study has shown that electrochemical properties of CGAs strongly depend on their chemical structure and electronic properties, particularly on the presence of electron-donating ?OH, ?CH═CH? and ?OCH₃ groups and strong electron-withdrawing ester (?COOR) group presented in their structure. The FTCP measurements of coffee samples show that their electrochemical behavior is very similar to that of CGAs. Therefore, FTCP can be used for characterization of CGAs and determination of their content in coffees. 5-O-Caffeoylquinic acid (5-CQA), prevailed CGAs in coffees, was used as a standard for quantification of total CGA content in coffee. The linear calibration curve of 5-CQA was observed within the concentration range of 5 to 100 μmol L^?1 with the limit of detection 5.7·10^?7 mol L^?1. The total CGA content of coffees has been expressed in 5-CGA equivalents per 100 g of coffee. It was shown that FTCP is a very sensitive, precise, and acurate method for determination of total CGA content in coffee. It should be noted that in presented investigation, FTCP was for the first time used for the study of electrochemical properties of polyphenolic antioxidants (including CGAs) and their characterization in some of the food samples.     

Acrylamide in espresso coffee: Influence of species,roast degree and brew length

Espresso coffees were analysed for acrylamide contents by matrix solid-phase dispersion and GC–MS. The influence of coffee species, roast degree, and brew length were ascertained. Mean acrylamide contents of medium roasted espressos (30 mL) were 1.16 ± 0.25 and 2.31 ± 0.43 μg for pure arabica and robusta samples, respectively. Espressos prepared from commercial blends contained an average acrylamide level of 1.26 ± 0.28 μg. A 25% decrease was observed when comparing espressos prepared with medium and dark roasted coffee. The extraction efficacy of acrylamide for standard espressos of 30 mL was near 80%, being only affected by brew volume, with long espressos (70 mL) containing practically all acrylamide of the coffee cake (99%), almost double that of short ones (20 mL). When compared with other common coffee beverages, espresso acrylamide concentration (μg/L) was higher. However, due to the small volume per cup, it may contribute less to acrylamide ingestion.     

Coffees rich in chlorogenic acid or N-methylpyridinium induce chemopreventive phase II-enzymes via the Nrf2/ARE pathway in vitro and in vivo

Recently, the coffee constituents 5-O-caffeoylquinic acid (CGA) and N-methylpyridinium (NMP) were identified as inducers of the Nrf2/antioxidant-response element (ARE) detoxifying pathway under cell-culture condition. To study the impact of CGA and NMP on the Nrf2-activating properties of a complex coffee beverage, two different model coffees were generated by variation of the roasting conditions: a low-roast coffee rich in CGA and a heavy-roast low in CGA but containing high levels of NMP. Activation of the Nrf2/antioxidant-response element pathway was monitored in vitro and in vivo.     

Occurrence of furan in coffee from Spanish market: Contribution of brewing and roasting

In this work, we evaluated the occurrence of furan in brews obtained from regular, decaffeinated, and instant coffee and commercial packed capsules. For this purpose, a previously developed automated headspace solid-phase microextraction method coupled to gas chromatography–mass spectrometry (HS-SPME-GC–MS) was used. Initially, the influence of HS-SPME conditions on furan formation was evaluated. In addition, the effect of roasting conditions (temperature and time) used for coffee beans on furan formation was also studied. We found that low temperature and long roasting time (140 °C and 20 min) decreases the final furan content. Furan concentrations in regular ground coffee brews from an espresso coffee machine were higher (43–146 ng/ml) than those obtained from a home drip coffee maker (20 and 78 ng/ml), while decaffeinated coffee brews from a home drip coffee maker (14–65 ng/ml) showed a furan concentration similar to that obtained from regular coffee. Relatively low concentrations of this compound (12–35 ng/ml) were found in instant coffee brews, while commercial packed coffee capsules showed the highest concentrations (117–244 ng/ml). Finally, the daily intake of furan through coffee consumption in Barcelona (Spain) (0.03–0.38 μg/kg of body weight) was estimated.     

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     

Bioactivities of low-grade green coffee and spent coffee in different in vitro model systems

Methanolic extracts of low-grade green coffee beans (LCB) and spent coffee were analysed for radical-scavenging activity (α,α-diphenyl-β-picrylhydrazyl radical) and oxygen radical absorbance capacity (ORAC). The extracts were also evaluated for anti-tumour (P388 cell assay), anti-inflammatory (J774A.1 cell assay) and anti-allergenic (RBL-2H3 cell line) activities in vitro. LCB extract was found to exhibit a radical-scavenging activity of 92.0% followed by spent Arabica (86.9%) and spent Robusta (82.0%) at a concentration of 50 ppm. The antioxidant activity of LCB extract, measured as Trolox equivalents (4416 μM/g) was significantly (p < 0.05) higher than that of the spent coffee extracts. However, extracts of spent coffee exhibited significantly (p < 0.05) more anti-tumour activity than the LCB extract in terms of cell viability. This could be due to the possible role of brown pigments (melanoidins and phenolic polymers), formed during roasting, which may protect cells from oxidative damage in the biological system. However, both the extracts of LCB and spent coffee showed limited anti-inflammatory and anti-allergic activities. The presence of phenolics and chlorogenic acids in appreciable quantities along with brown pigments makes these coffee by-products a source for natural antioxidants.     

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.     

Extraction of coffee diterpenes and coffee oil using supercritical carbon dioxide

Commercial green and roasted coffee beans were used to maximize oil extraction and conditions were studied to obtain the highest and lowest diterpene levels on green and roasted coffee oil, respectively. Thus, operational temperatures (60–90 °C) and pressure (235–380 bar) were optimized for coffee oil extraction. Oil content levels and diterpene oil concentration were compared to the results obtained with the extraction with Soxhlet apparatus, using hexane as solvent. In general, an inverse correlation was observed between the amount of extracted oil and diterpene concentration levels. As a result, different oil contents with different diterpene concentrations could be obtained. The HPLC analysis of cafestol and kahweol in the oil extracted from green coffee beans at 70 °C/253 bar resulted in the highest concentration (453.3 mg 100 g⁻¹), which was 48% lower than in the oil extracted with hexane while in the oil extracted from roasted coffee beans at 70 °C/371 bar, resulted in 71.2% reduction of diterpenes.     

Inhibitory effects of chlorogenic acids from green coffee beans and cinnamate derivatives on the activity of porcine pancreas α-amylase isozyme I

Nine kinds of chlorogenic acids (CGAs) account for 80% of the total CGA content in green coffee beans. They consist of three subgroups of caffeoylquinic acids (CQAs), feruloylquinic acids (FQAs), and dicaffeoylquinic acids (diCQAs). We previously reported the inhibitory effects of 5-CQA on porcine pancreas α-amylase (PPA) isozymes, PPA-I and PPA-II. In this paper, we investigated the PPA-I inhibition by eight kinds of CGAs. The IC₅₀ values of CQAs, FQAs, and diCQAs against the PPA-I-catalysed hydrolysis of p-nitrophenyl-α-D-maltoside were 0.08–0.23 mM, 1.09–2.55 mM, and 0.02–0.03 mM, respectively. All CQAs and FQAs and 3,5-diCQA showed mixed-type inhibition with binding to the enzyme–substrate complex (ES) being stronger than to the enzyme (E). 3,4-DiCQA and 4,5-diCQA showed mixed-type inhibition, but, conversely are suggested to bind to E stronger than ES.     

Chlorogenic acids and related compounds in medicinal plants and infusions

The consumption of plant infusions for prevention and treatment of health disorders is a worldwide practise. Various pharmacological activities inherent to medicinal plants have been attributed to their phenolic composition, including chlorogenic acids (CGA). Studies have shown potential beneficial properties of CGA to humans such as antioxidant, hepatoprotective, hypoglycaemic. In the present study, the CGA composition of 14 dried medicinal plants was determined by HPLC-UV and LC-DAD–ESI-MS. The plants with the highest CGA contents were Ilex paraguariensis, Bacharis genistelloides, Pimpinella anisum, Achyrochine satureioides, Camellia sinensis, Melissa officinalis and Cymbopogon citratus, with 84.7 mg/100 g–9.7 g/100 g, dry weight. Plant infusions were prepared (at 0.5%) in order to evaluate the actual consumption of CGA through these beverages. Total CGA contents in the infusions were similar to those in the methanolic extracts and indicated that a satisfactory extraction occurs during the preparation of infusions. These CGA-rich plants deserve attention regarding the pharmacological properties attributed to CGA.     

Norharman and harman in instant coffee and coffee substitutes

Norharman and harman are two neuroactive β-carbolines present in several plants and thermally processed foods, including roasted coffee. The objective of this study was to evaluate their amounts in commercial instant coffee-based and coffee substitute beverages (n = 48), with variable amounts of coffee, chicory, barley, malt, and rye. All samples contained variable amounts of both β-carbolines, always with a higher proportion of norharman than harman. The highest levels (p < 0.01) were found in 100% instant coffees, with mean amounts of 3.8 μg/g and 1.5 μg/g for NH and H, respectively, followed by plain chicory. The lowest amounts were found in 100% barley, with 1.1 μg/g for NH and 0.3 μg/g for H. The NH and H content was statistically higher (p < 0.01) in all mixtures with coffee when compared to those without it. Nevertheless, and except for 100% barley, the amounts provided by beverages based on coffee substitutes are within those reported for standard coffee brews.     

Antioxidant activity,polyphenols, caffeine and melanoidins in soluble coffee: The influence of processing conditions and raw material

The production of soluble coffee starts with the selection of beans and is followed by roasting, grinding, extraction and drying. Lyophilised soluble coffees extracted by various methods from light, medium and dark-roasted arabica and robusta beans were evaluated for antioxidant activity (AA) using ABTS, Folin, DPPH and FRAP techniques. Caffeine, chlorogenic acid (5-CQA) and melanoidin content was also quantified. The data were analysed by principal component analysis. The AA values derived from the various methods used were correlated. Roasting resulted in the degradation of 5-CQA and formation of melanoidins, while AA was largely unaffected by roasting. The extraction of soluble coffee more prominently affected the AA of light-roasted coffee, mainly because it favoured the extraction of 5-CQA. The larger caffeine content in robusta coffee resulted in greater AA. All of soluble coffee products studied possessed antioxidant potential, which was conferred by their concentrations of phenolic compounds, caffeine and melanoidins.     

Identification of Chemical Clusters Discriminators of Arabica and Robusta Green Coffee

The chemical parameters pH, soluble solids, caffeine, trigonelline, total chlorogenic acids, total caffeoylquinic acids, 3-O-caffeoylquinic acid, 4-O-caffeoylquinic acid, 5-O-caffeoylquinic acid, total dicaffeoylquinic acids, 3,4-O-dicaffeoylquinic acid, 3,5-O-dicaffeoylquinic acid, 4,5-O-dicaffeoylquinic acid, total feruloylquinic acids, 3-O-feruloylquinic acid, and 5-O-feruloylquinic acid were measured in Arabica (C. arabica) and Robusta (C. canephora) green coffees in order to determine discrimination parameters. In general, Robusta green coffee showed higher values for pH, soluble solids, caffeine, total caffeoylquinic acids, total dicaffeoylquinic acid, and total feruloylquinic acid, but the content of soluble solids was not significantly different in both species of green coffee. Through application of a multivariate analysis, it was concluded that these chemicals form three clusters, being the group of caffeine, trigonelline, 3-O-caffeoylquinic acid, 4-O-caffeoylquinic acid, 3-O-feruloylquinic acid, 5-O-feruloylquinic acid, 3,4-O-dicaffeoylquinic acid, 3,5-O-dicaffeoylquinic acid, and 4,5-O-dicaffeoylquinic acid highly discriminating for Arabica and Robusta green coffees.     

Tocopherols in espresso coffee: Analytical method development and validation

The present paper reports the development and validation of an analytical micro-method for tocopherols quantification in espresso coffee by normal-phase HPLC with fluorescence detection. The proposed method consists in a liquid–liquid extraction with n-hexane:ethyl acetate, followed by a clean-up with dimethylformamide to eliminate co-eluting interferences. The method showed good intra- and inter-day precisions (coefficient of variation < 6.5%), good accuracies (98 ± 6%), and high correlation coefficients (r > 0.999) for standards subjected to the entire procedure. Only α- and β-tocopherols were identified in the brews. The detection and quantification limits were 0.5 and 1.4 ng/ml, for α-tocopherol, and 0.4 and 1.1 ng/ml, for β-tocopherol, respectively. A mean total tocopherol content (α + β) of 3.5 ± 0.9 μg in commercial espresso coffee blends (30 ml) was detected. The proposed method requires low solvent consumption and proved to be sensitive, precise and accurate.     

Discrimination between Arabica and Robusta green coffee using visible micro Raman spectroscopy and chemometric analysis

We have applied visible micro Raman spectroscopy combined with principal component analysis (PCA) as a powerful technique for the fast discrimination between the two coffee species, Arabica and Robusta, based on their chlorogenic acid (CGA) and lipid contents. The Raman spectra reveal different CGA and lipid compositions when comparing Arabica and Robusta green coffee. Analysing the whole Raman spectrum, the PCA yielded a clear separation between Arabica and Robusta with 93% of the total spectral variation. Here, the most significant spectral range lies between 1000 and 1750 cm⁻¹ and is dominated by the Raman bands of CGA. Also, by restricting the PCA analysis to the spectral range from 2700 to 3050 cm⁻¹, which is dominated by lipid bands, a reliable discrimination between the two coffee species could be achieved. In this case, the first two principal components of the PCA accounted for 85% of the explained total spectral variation.     

多因素交互作用导致烘焙咖啡中绿原酸快速降解

研究烘焙温度、时间及基质pH值对咖啡绿原酸的影响,采用小粒生咖啡豆进行不同程度的烘焙实验,分析不同烘焙温度和时间下pH值、质量损失率、水分质量分数、新绿原酸含量、绿原酸含量、隐绿原酸含量及3 种异绿原酸异构体的变化情况,并建立绿原酸降解动力学模型,采用化学反应模型验证绿原酸单体的降解情况。结果表明,烘焙咖啡中水分质量分数、质量损失率随烘焙温度的升高总体分别呈降低和升高的趋势,随烘焙时间的延长分别呈降低和升高的趋势。绿原酸含量随烘焙温度升高和时间延长显著降低（P＜0.05）,相比生咖啡豆,新绿原酸、隐绿原酸含量随烘焙温度升高先升高后降低,随烘焙时间延长显著降低（P＜0.05）。新绿原酸、隐绿原酸含量与咖啡pH值和烘焙时间呈显著负相关（P＜0.05）,绿原酸含量与烘焙温度、时间呈显著负相关（P＜0.05）,与咖啡水分质量分数呈显著正相关（P＜0.05）。温度和时间的交互作用均对咖啡绿原酸类化合物降解产生高度显著影响（P＜0.001）。绿原酸3 种异构体热降解符合一级反应动力学模型。在化学反应模型中,绿原酸转化为新绿原酸和隐绿原酸两种异构体,3 种异构体质量浓度均随pH值和温度的升高显著降低（P＜0.05）,温度与pH值交互作用对绿原酸降解影响高度显著（P＜0.001）。综上,温度、时间及pH值的协同作用致使烘焙咖啡中绿原酸的快速降解。