Article

Influence of Water Pressure on the Final Quality of Arabica Espresso Coffee. Application of Multivariate Analysis

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Abstract

Water pressure is one of the most important factors which influence the final quality of espresso coffee (EC). However, few studies dealing with this issue have been found. The aim of this work was to study the effect of water pressure on the final quality of Arabica ECs as well as to classify ECs prepared at different pressures (7, 9, and 11 atm) according to their physicochemical and sensory characteristics, key odorants, by means of multivariate analysis. Statistically, principal component 1 (PC1) separated ECs prepared at 7 and 9 atm from ECs prepared at 11 atm and included the main foam and taste characteristics as well as some key odorants and flavor compounds. ECs prepared at 7 and 9 atm were separated by principal component 2 (PC2). Coffees prepared at 9 atm showed consistency of foam and a high percentage of key odorants related to freshness and fruity, malty, and buttery flavors. A simple discriminate function was obtained by discriminate analysis, allowing the classification of ECs prepared at three pressures into their respective groups with a success rate of 100%.

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... During extraction, soluble compounds are dissolved and, depending on the extraction technique, non-soluble compounds are washed away with the extraction water, ending up in the extract as dissolved or suspended solids [10][11][12][13][14][15]. Many different extraction techniques have been introduced over the past centuries, which vary according to factors such as geography, culture and social context, as well as personal preferences; these different factors can extracted at 7 or 9 bar [19]. In these previous studies, the authors focused on the composition and sensorial attributes of the final cup in order to assess the impact of water temperature and pressure on espresso preparation. ...
... For PC2, 18 tentatively identified compounds had positive scores and are related to high pressure extraction. All but four of the compounds (18,19,22,29) belong to the most polar groups A, B or C. Compounds with negative scores for PC2 belonged to families D and E, together with compounds number 2, 6, 12, 13 and 14 from the other families. Negative PC2 scores are related to an increased area under the curve for higher extraction temperatures, indicating that increases in temperature had a greater effect on the less polar compounds. ...
... Pressure is the driving force required to produce a flow of water through the compacted coffee cake, assisting the extraction of compounds trapped inside the coffee particle structure, and also helping to transfer solid particles and oil droplets from the ground beans to the cup [15]. Some authors have reported an increase in chlorogenic acids, lipids, coffee oil, diterpenes and aroma compounds when increasing pressure from 7 to 9 bar [19,29] although no differences in caffeine or total solids were observed. A further pressure increase to 11 bar had either no effect or produced a decrease in the above compounds. ...
Article
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The hot-water extraction process used to make an espresso coffee is affected by a large number of factors. A proper understanding of how these factors impact the profile of the final cup is important to the quality of an espresso coffee. This work examines the effect of water temperature and pressure on the extraction kinetics of volatile organic compounds (VOCs) in coffee. This was achieved by on-line monitoring of the volatiles directly from the coffee flow, using proton-transfer-reaction time-of-flight mass-spectrometry (PTR-ToF-MS). Using hierarchical cluster analysis (HCA), tentatively identified compounds were grouped into 5 families according to their time intensity profiles. VOCs grouped into each family had similar physicochemical properties while polarity was found to be one of the main forces driving VOC extraction kinetics. The effect of pressure was studied by extracting espresso coffees at 7, 9 and 11bar. A pressure of 11bar resulted in an increased extraction of volatiles over the entire extraction time (25 s). To study the effect of temperature, espresso coffees were extracted at 82, 92 and 96°C. An increase in temperature produced a significant increase in the extraction of VOCs, especially during the last part of the extraction. The effect of temperature on extractability was more pronounced for the less polar compounds.
... EC is capable of delivering moderate levels of diterpenes; however, there is limited information regarding the influence of parameters of brewing procedures on the levels of cafestol and kahweol per cup. Although the chemical composition of ECs as affected through different coffee/water ratio [20,21], particles size [21,22], extraction temperature [21,23,24] and water pressure [24,25] has already been reported, scarce information [21] was found in the literature with respect to diterpenes content of ECs prepared under different conditions. Considering the significant consumption of EC among European countries, studying the effect of operating conditions on diterpenes content of EC becomes relevant. ...
... Different pressures resulted in ECs with lipid concentration ranging from 1.59 ± 0.10 (7 bar) to 2.62 ± 0.13 mg/mL (9 bar). According to the literatures [6,25,35], the concentration of lipid in the ECs can vary in accordance with applied pressure. Entrance of water into area of matrices due to the presence of pressure may assist extraction of particular compounds which are trapped in the matrix pores [34]. ...
... Entrance of water into area of matrices due to the presence of pressure may assist extraction of particular compounds which are trapped in the matrix pores [34]. According to Andueza et al. [25], increasing the water pressure from 7 to 9 bar caused significant elevation in total lipid content of analyzed ECs. However, by continuing the pressure increasing to 11 bar, ECs indicated less lipid concentration. ...
Article
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The aim of the present study was to evaluate the effect of preparation conditions of espresso coffee (EC) on the diterpenes profile. ECs were prepared from roasted and ground (R&G) Arabica coffee and analyzed for the content of cafestol and kahweol by liquid–liquid extraction followed by HPLC-DAD, as well as their lipid content. The main variables in the present study were as follows: the water quantity, the amount of coffee, the particle size, the percolation time, the water temperature and pressure. Average cafestol, kahweol and lipid content of R&G Arabica coffee were 467 ± 20 mg/100 g, 638 ± 33 mg/100 g and 15.1 ± 0.1 g/100 g, respectively. Although all parameters influenced the diterpenes content of ECs (21 samples), the particle size and water quantity were the most significant ones. It was possible to reduce the total diterpenes from 58.8 ± 0.7 mg/L (2.3 mg/40 mL) to 30.7 ± 0.8 mg/L (1.2 mg/40 mL) by varying the brewing conditions. The average extraction yield of diterpenes and lipids was in the range of 1.5–2.5 and 7.0–9.0 %, respectively. Regarding total cafestol and kahweol, very fine particles seem to be more desirable for the production of highly concentrated brew (2.3 mg/40 mL) with cafestol and kahweol extraction yields of 2.8 and 2.9 %, respectively, than other studied ECs. On the other hand, samples brewed at 70 °C exhibited lower diterpenes content (1.2 mg/40 mL) and diterpenes extraction efficiency (1.4 %) with respect to all other considered parameters. This study clearly shows that parameters for coffee brew preparation may be changed to modify the diterpenes content of ECs according to the desired purpose.
... Also, various studies have been carried out on the characterization of the flavor and headspace volatile profile of filter coffee, espresso coffee, plunger coffee, and various coffee brews, as well as the effect of factors such as roasting conditions, grinding degree, water/coffee ratio, and brew preparation conditions on the headspace volatiles and flavor attributes of these coffees. [13,14,[19][20][21][22][23][24][25][26][27][28][29][30][31][32] For the isolation of the volatile compounds coffee extraction methods such as, direct headspace sampling, solid phase micro extraction (SPME), and purge and trap have been used in various studies. [13,14,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] SPME is the most widely used method for evaluation of headspace volatiles of coffee due to being a fast, cheap, reliable, and reproducible method. ...
... [13,14,[19][20][21][22][23][24][25][26][27][28][29][30][31][32] For the isolation of the volatile compounds coffee extraction methods such as, direct headspace sampling, solid phase micro extraction (SPME), and purge and trap have been used in various studies. [13,14,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] SPME is the most widely used method for evaluation of headspace volatiles of coffee due to being a fast, cheap, reliable, and reproducible method. ...
... Likewise in this study it was found that as the roast degree increased the intensity of roasted/burnt, bitter and earthy flavor characteristics of Turkish coffee increased, while sweet character decreased. In studies on filter and espresso coffees, during sensory analysis fruity, flowery, and buttery characters were identified, [14,19,[23][24][25][26][27] but in this study the mentioned characters were not identified in any of the Turkish coffee samples, which could be a result of the different preparation style of the brew as there may be flavor losses during brewing, namely during boiling. Also Turkish coffee is prepared from very finely ground roasted coffee and grinding grade can also affect the chemical and sensorial characteristics of coffee brews as stated in a study on espresso coffee. ...
Article
The characteristic volatiles of light, medium and dark roasted Turkish-style boiled coffee brews were studied by head space solid-phase micro extraction/gas chromatography-mass spectrometry and sensory flavour profile analysis. Sixty five volatile compounds, including furans, pyrazines, pyrroles, phenols, pyridines, ketones, oximes, alcohols, aldehydes, thiophenes, benzenes and terpenes, were isolated from Turkish-style boiled coffee samples. The flavour profile analysis showed Turkish coffee brews as roasted/burnt, spicy, bitter, acidic, sweet, salty, astringent (dry), woody, fermented, earthy and tobacco-like flavour characteristics. It was concluded that Turkish coffee was rich in furans, pyrazines, pyrroles and phenols giving its roasted/burnt, spicy, woody and fermented flavour characteristics.
... Driving forces are generated by a pressurized pump, a vapor-pressurized chamber, and the force of gravity in espresso, moka, and filter coffees, respectively. One report suggested that the pressure of the extracting hot water also influences the physicochemical, textural, and sensory attributes of EC (Andueza et al., 2002). A total of 40.71% variability was found in the overall physical, sensory and compositional attributes of EC while extracting from 7 to 11 atm pressure. ...
... The coffee prepared at the highest extraction pressures was bitter and astringent with a more intense aftertaste. From an odorant point of view, some key odorants, like 2-methylbutanal, 3-methylbutanal, and 2-ethyl-3,5-dimethylpyrazine, are also found at their highest levels in EC, which brings about cereal/malty and burnt/roasted off-notes in EC (Andueza et al., 2002). Coffee extracted at the lowest water pressure (that is, 7 atm) has an unstable/inconsistent foam index, while coffee prepared at 9 atm has a foam consistency similar to that of coffee prepared at 11 atm. ...
... The significant difference in EC prepared at low pressure and at 9 atm is the variation in foam index and foam consistency. On the other hand, ECs prepared at 9 and 11 atm differ mainly in sensory and compositional features (Andueza et al., 2002). Coffee prepared at 9 atm is ideal with respect to foam index and foam consistency, and it has a desired level of key odorants related to cup quality. ...
Article
Full-text available
The production and consumption of coffee are increasing despite the roadblocks to its agriculture and global trade. The unique, refreshing, and stimulating final cupping quality of coffee is the only reason for this rising production and consumption. Coffee quality is a multifaceted trait and is inevitably influenced by the way it is successively processed after harvesting. Reportedly, 60% of the quality attributes of coffee are governed by postharvest processing. The current review elaborates and establishes for the first time the relationship between different methods of postharvest processing of coffee and its varying organoleptic and sensory quality attributes. In view of the proven significance of each processing step, this review has been subdivided into three sections, secondary processing, primary processing, and postprocessing variables. Secondary processing addresses the immediate processing steps on the farm after harvest and storage before roasting. The primary processing section adheres specifically to roasting, grinding and brewing/extraction, topics which have been technically addressed more than any others in the literature and by industry. The postprocessing attribute section deals generally with interaction of the consumer with products of different visual appearance. Finally, there are still some bottlenecks which need to be addressed, not only to completely understand the relationship of varying postharvest processing methods with varying in‐cup quality attributes, but also to devise the next generation of coffee processing technologies.
... tamping) are the most important. 28 Some of these variables have been studied, 23,29 -32 such as the effects of grinding grade, chemical composition of water, temperature and pressure of water, 15,24,25,31,33 while no scientific details have focused on the effects of tamping on EC quality. Moreover, no information on the effects of their variance and on the quality of EC have been reported, although its importance was recognized from Illy and Viani and Andueza et al. 3,24 The particle size distribution of coffee grounds generally shows a high variance due to the mixture of coffee beans (i.e. the variability in mechanical properties of each coffee variety), the type of grinder, the type of burrs of the grinder as well as the burr wear. ...
... From Eqn (2) caffeine concentrations of 5.87, 4.41 and 2.55 mg mL −1 were estimated after 14 s of extraction, respectively, for samples prepared using a grinding grade of 6, 6.5 and 7. Also, after 30 s, values of 2.46, 1.85 and 1.07 mg mL −1 were respectively estimated. The estimated data are in agreement with Andueza et al., 23,24 who reported a caffeine concentration between 2.01 ± 0.05 and 3.80 ± 0.07 mg mL −1 . However, also for this quality attribute, a high variability of experimental data was observed, which may be attributed to the variance in particle size distribution. ...
... Again, by considering the time necessary to prepare a regular coffee of 25 mL, solid contents between 31.76 and 57.04 mg mL −1 were estimated when the finest and coarsest fractions, respectively, of the coffee grounds at the level of 6.5 were used. These data are in agreement with Andueza et al., 23,24 who reported a solid concentration in the range of 34.59 and 42.74 mg mL −1 performing an EC extraction until a total volume of 40 mL was reached. Similar results were obtained for samples obtained using grinding levels of 6 and 7, for which a solid concentration between 52.4 and 39.02 mg mL −1 and between 26.26 and 32.5 mg mL −1 respectively, were estimated. ...
Article
Background: To improve the quality of espresso coffee, the variables under the control of barista, such as grinding grades, coffee quantities and pressure applied on coffee cake as well as their variance are of great importance. A nonlinear mixed effect modeling was used to obtain information on the changes in chemical attributes of espresso coffee (EC) as a function of the variability of extraction conditions. Results: During extraction, the changes in volume were well described by a logistic model while the chemical attributes were better fit by a first order kinetic. The major source of information was contained into the grinding grade which accounted for the 87-96% of the variance of experimental data. The variability of the grinding produced changes in caffeine content in the range of 80.03 mg and 130.36 mg when using a constant grinding grade of 6.5. Conclusion: The variability in volume and chemical attributes of EC is large. The grinding had the most important effect showing as the variability in particle size distribution observed for each grinding level had a profound effect on the quality of EC. The standardization of the grinding would be of crucial importance for obtaining all espresso coffees with a high quality standard.
... Driving forces are generated by a pressurized pump, a vapor-pressurized chamber, and the force of gravity in espresso, moka, and filter coffees, respectively. One report suggested that the pressure of the extracting hot water also influences the physicochemical, textural, and sensory attributes of EC (Andueza et al., 2002). A total of 40.71% variability was found in the overall physical, sensory and compositional attributes of EC while extracting from 7 to 11 atm pressure. ...
... The coffee prepared at the highest extraction pressures was bitter and astringent with a more intense aftertaste. From an odorant point of view, some key odorants, like 2-methylbutanal, 3-methylbutanal, and 2-ethyl-3,5-dimethylpyrazine, are also found at their highest levels in EC, which brings about cereal/malty and burnt/roasted off-notes in EC (Andueza et al., 2002). Coffee extracted at the lowest water pressure (that is, 7 atm) has an unstable/inconsistent foam index, while coffee prepared at 9 atm has a foam consistency similar to that of coffee prepared at 11 atm. ...
... The significant difference in EC prepared at low pressure and at 9 atm is the variation in foam index and foam consistency. On the other hand, ECs prepared at 9 and 11 atm differ mainly in sensory and compositional features (Andueza et al., 2002). Coffee prepared at 9 atm is ideal with respect to foam index and foam consistency, and it has a desired level of key odorants related to cup quality. ...
... Driving forces are generated by a pressurized pump, a vapor-pressurized chamber, and the force of gravity in espresso, moka, and filter coffees, respectively. One report suggested that the pressure of the extracting hot water also influences the physicochemical, textural, and sensory attributes of EC (Andueza et al., 2002). A total of 40.71% variability was found in the overall physical, sensory and compositional attributes of EC while extracting from 7 to 11 atm pressure. ...
... The coffee prepared at the highest extraction pressures was bitter and astringent with a more intense aftertaste. From an odorant point of view, some key odorants, like 2-methylbutanal, 3-methylbutanal, and 2-ethyl-3,5-dimethylpyrazine, are also found at their highest levels in EC, which brings about cereal/malty and burnt/roasted off-notes in EC (Andueza et al., 2002). Coffee extracted at the lowest water pressure (that is, 7 atm) has an unstable/inconsistent foam index, while coffee prepared at 9 atm has a foam consistency similar to that of coffee prepared at 11 atm. ...
... The significant difference in EC prepared at low pressure and at 9 atm is the variation in foam index and foam consistency. On the other hand, ECs prepared at 9 and 11 atm differ mainly in sensory and compositional features (Andueza et al., 2002). Coffee prepared at 9 atm is ideal with respect to foam index and foam consistency, and it has a desired level of key odorants related to cup quality. ...
... Authors found amounts of caffeine in pod-brewed coffees (pure Arabica, pure Robusta, and blends) ranging from 2.59 mg/mL to 4.65 mg/mL. Furthermore, our data fell within the range of values found by Andueza et al. 22 under similar conditions of pressure and temperature, reporting an average of caffeine around 2 mg/mL. On the contrary, a recent paper of Jeon et al. 23 showed lower values (<1 mg/mL) in home-made coffees prepared with grounded coffee beans packed in paper filters and extracted with hot water (no information on pressure available). ...
... Concerning CGA concentrations, our data confirmed the ranges reported by Moeenfard et al. 28 , with particular high amounts of 3-CQA and 5-CQA (about 1 mg/mL each) for ECs #D-49 and #D-50 (Supplementary Table 4). These 5-CQA concentrations close to 1 mg/mL, two-to five-fold higher than those recorded for most of the capsule ECs (Supplementary Table 4), were also registered by Andueza et al. 22,30 for a set of blended ECs brewed under different extraction conditions. Table 2 also shows that ECs belonging to brand C had the highest content in the sum of these phenolics, hitting an average 118.0 ± 18.5 mg/serving, while brand D coffees had the lowest values, with an average of 83.7 ± 12.8 mg/serving. ...
... Nevertheless, this pattern could be currently attributed to i) the impact that the brewing machine used might have on the extraction of coffee bioactives or ii) the main processing steps used within each company for the preparation of all their capsules. In this regard, Andueza et al. 22 Table 3. Inter-lot variation in the content of main capsule espresso coffee phytochemicals. n-CQA: n-Ocaffeoylquinic acid; NMP: N-methylpyridinium. ...
Article
Full-text available
Coffee is one of the most popular beverages worldwide and, nowadays, one of the most practical way for its preparation is by prepacked capsules. The aim of this study was comparing the content in caffeine, trigonelline, N-methylpyridinium (NMP), niacin, and chlorogenic acids of 65 different capsule-brewed coffees, commercialised by 5 of the most representative brands in Italy. Coffees were prepared from capsules following manufacturer’s instructions and analysed with an optimized UHPLC-MS/MS method able to assess all these phytochemicals in one single run. Inter-lot and capsule variability were also studied for a subset of coffee capsules. Except for decaffeinated coffees, caffeine amount accounted between 54 and 208 mg/serving. Regular espresso coffees showed higher trigonelline, NMP, and niacin concentrations than large (lungo) and decaffeinated samples, with average serving amounts of 17.96, 1.78, and 0.66 mg, respectively. Regarding chlorogenic acids, caffeoylquinic acids were the most relevant ones (20–117 mg/serving). Feruloylquinic acids were quantified between 8 and 50 mg/serving. Coumaroylquinic acids, hydroxycinnamate dimers, caffeoylshikimic acids, and caffeoylquinic lactones were also present at lower concentrations. Multivariate analysis provided comprehensive information on the phytochemical profile of the different types of coffee, showing a great variability among coffees with some brand-related insights. This study supports the need for accurately characterizing espresso coffees while investigating the beneficial effects of coffee on human health.
... EC is capable of delivering moderate levels of diterpenes; however, there is limited information regarding the influence of parameters of brewing procedures on the levels of cafestol and kahweol per cup. Although the chemical composition of ECs as affected through different coffee/water ratio [20,21], particles size [21,22], extraction temperature [21,23,24] and water pressure [24,25] has already been reported, scarce information [21] was found in the literature with respect to diterpenes content of ECs prepared under different conditions. Considering the significant consumption of EC among European countries, studying the effect of operating conditions on diterpenes content of EC becomes relevant. ...
... Different pressures resulted in ECs with lipid concentration ranging from 1.59 ± 0.10 (7 bar) to 2.62 ± 0.13 mg/mL (9 bar). According to the literatures [6,25,35], the concentration of lipid in the ECs can vary in accordance with applied pressure. Entrance of water into area of matrices due to the presence of pressure may assist extraction of particular compounds which are trapped in the matrix pores [34]. ...
... Entrance of water into area of matrices due to the presence of pressure may assist extraction of particular compounds which are trapped in the matrix pores [34]. According to Andueza et al. [25], increasing the water pressure from 7 to 9 bar caused significant elevation in total lipid content of analyzed ECs. However, by continuing the pressure increasing to 11 bar, ECs indicated less lipid concentration. ...
... According to scientific literature, these conditions may be considered as the most common for EC preparation. 7,8,[11][12][13]42 Instead, the value of pressure was chosen on the basis of preliminary experiments in which different weights were used to press ground coffee. ...
... However, a high variance in the total solids content of EC has been reported in the literature. 7,8,47 Caffeine contents of the regular EC between 3.212 ± 0.267 and 4.179 ± 0.209 mg/mL were observed. These values were higher than those reported by Caporaso et al. 47 and Parenti et al., 46 which showed values always lower than 2.44 mg/mL. ...
... As well-known, the EC may be affected by several variables, such as roasting grade, mixture of roasted coffee varieties, water temperature, etc. 3−7 In addition, the volume of EC, which considerably affects the chemical composition of brew, is often highly variable among the scientific publications. 7,8,46,47 However, from Table 3, the analysis of the changes in chemical attributes of the three fractions of EC showed structured variations. The pH values significantly increased as a function of the fraction of brew for each grinding grade. ...
Article
The changes in chemical attributes and aromatic profile of espresso coffee were studied taking into account the extraction time and the grinding level as independent variables. Particularly, by using an Electronic Nose System the changes of the global aromatic profile of EC were highlighted. The results showed as the major amount of organic acids, solids and caffeine were extracted in the first 8 seconds of percolation. The grinding grade significantly affected the quality of EC probably as effect of the particle size distribution and the percolation pathways of water through the coffee cake. The use of Electronic Nose System allowed to discriminate the fractions of the brew as a function of percolation time and also the regular coffees obtained from different grinding grades. Particularly, the aromatic profile of a regular coffee (25 mL) was significantly affected by grinding level of coffee ground and percolation time which are two variables under the control of bar operator.
... It tests the effects of different brewing settings (i.e. pressure and temperature) on the physical and chemical parameters of EC, as parameters such as water temperature and pressure are recognized as being particularly important for the quality of traditional espresso coffee (Andueza et al., 2002(Andueza et al., , 2003. Furthermore, the method is compared to a capsule method in order to highlight differences in physical and chemical parameters between the new method and a commercial method. ...
... 2. The extraction process is partially static (infusion) inside the hermetically sealed extraction chamber under high pressure, whereas in the conventional process extraction takes place under dynamic conditions during percolation. 3. The process takes place under a range of pressures that are far above conventional values (i.e. higher than 15 bar vs. 9 bar in the conventional process) (Andueza et al., 2002). 4. The extraction temperature is regulated by the temperature of the incoming water (which is heated outside the extraction chamber) and the temperature of the chamber itself (which has a separate thermostat) whereas in the conventional method it depends solely on the temperature of the percolating water. ...
... pH values are in the range 5.2-5.8 and consistent with those reported in literature. Andueza et al. (2002), and Dalla Rosa et al. (1986) studied the effect of the water pressure (7-11 bar), and cake compression on pH values. In these studies, increased pressure decreased pH. ...
Article
A new espresso brewing method has recently been developed. The main steps are: introduction and tamping of ground coffee in a sealed chamber, introduction of pressurized air into the chamber, the introduction of hot water and a pre-infusion phase. It is substantially different to the usual brewing method used in bars: the driving force for the flow is the pressure difference between the interior and the exterior of the chamber (rather than pressurized hot water provided by a motor-driven pump); the extraction process is partially static; the pressure is higher than the traditional method; and the temperature of the extraction chamber can be controlled (in addition to the water temperature control found in the traditional method). The method has been tested with three chamber temperatures and two pressures. At all settings, espressos produced using this method have particularly high and persistent foam. Furthermore, changes in pressure cause changes in some physical parameters and the amount of key odorants in the headspace above the coffee. A benchmark comparison with the capsule method gives differences in several aromatic compounds and in almost all the physical parameters. In conclusion, the beverage produced by the CF method is clearly recognizable by a thick and very persistent foam layer, while the method appears more flexible than the traditional one as the characteristics of the EC can be adjusted as a function of brewing conditions.
... The [92]. In the study by Parenti et al. (2014) [91], new methods of preparing coffee in a machine were used: Hyper Espresso Method (HIP, capsules), I-Espresso System (capsules), and the conventional espresso machine method (CM, using ground coffee). ...
... The obtained caffeine values ranged from 2.16 ± 0.30 to 2.39 ± 0.26 mg/mL (about 0.002 g/L). Similarly, Andueza et al. (2002) [92] did not notice any effect of higher pressure on the extraction of caffeine in the brew (pressure range approximately 7 bar, 9 bar, 11 bar): 2.0 ± 0.03, 2.05 ± 0.03, and 2.01 ± 0.05 mg/mL (about 0.002 g/L). These studies were not included in this literature review due to the lack of information about species of coffee. ...
... The obtained caffeine values ranged from 2.16 ± 0.30 to 2.39 ± 0.26 mg/mL (about 0.002 g/L). Similarly, Andueza et al. (2002) [92] did not notice any effect of higher pressure on the extraction of caffeine in the brew (pressure range approximately 7 bar, 9 bar, 11 bar): 2.0 ± 0.03, 2.05 ± 0.03, and 2.01 ± 0.05 mg/mL (about 0.002 g/L). These studies were not included in this literature review due to the lack of information about species of coffee. ...
Article
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Coffee brews are one of the most popular drinks. They are consumed for caffeine and its stimulant properties. The study aimed to summarize data on the influence of various factors on caffeine content in brews prepared with different methods. The study was carried out using a literature review from 2010–2020. PubMed and Google Scholar databases were searched. Data on caffeine content was collected by analyzing the following factors: the influence of species, brewing time, water temperature, pressure, degree of roast, grinding degree, water type, water/coffee ratio as well as other factors (such as geographical origin). To sum up, converting caffeine content to 1 L of the brew, the highest content is that of brews prepared in an espresso machine (portafilter), with the amount of 7.5 g of a coffee blend (95% Robusta + 5% Arabica), and water (the volume of coffee brew was 25 mL) at a temperature of 92 °C and a pressure of 7 bar, but the highest content in one portion was detected in a brew of 50 g of Robusta coffee poured with 500 mL of cold water (25 °C) and boiled.
... Extensive studies have been focused on the effect of different physical variables during the percolation process on the extraction of caffeine, CGA, key aroma compounds and sensory analysis (Andueza, de Peña, & Cid, 2003;Andueza et al., 2002;Gloess et al., 2013;Illy & Viani, 2005;López-Galilea, de Peña, & Cid, 2007;López-Galilea, Fournier, Cid, & Guichard, 2006;Maeztu et al., 2001). Ludwig et al. (2012) investigated the extraction behavior of the main coffee antioxidants (caffeoylquinic acids, melanoidins, and caffeine) and the antioxidant capacity, during brewing time in the most widely consumed coffee brew methods (filter and espresso) in coffee. ...
... Different coffeemakers, single-dose units (pods, and capsule), and ground coffee with different origin and likely roasting degree are used in this investigation. There are many physical parameters governing the extraction such as temperature inside the cake, the pressure above and under the cake, percolation time, dose, particle size and shape, compacting of the bed, etc (Albanese et al., 2009;Andueza et al., 2002;Andueza et al., 2003;Illy & Viani, 2005;Petracco, 2005). Table 2 summarizes the chemical characterization of fraction F5 for samples F, B, NB, and NC in terms of total carbohydrate, caffeine, CGA, melanoidins, total solids content, browning, and antioxidant capacity. ...
Article
Coffee melanoidins have attracted interest as a result of its potential health benefits. This investigation aims to elucidate the extraction behavior of melanoidins and their populations during the preparation of portioned espresso coffee and its relationship with the antioxidant activity of the coffee brew. Filter-paper pods, FAP capsule, and clone capsule containing light roasted coffee have been investigated. An accumulative fractionation approach has applied to model the extraction kinetics of melanoidins, melanoidin populations, browning, chlorogenic acids (CGA), and antioxidant activity. Melanoidins were very efficiently extracted in clone capsules since less than 9 s was necessary to extract the 50% of the melanoidin content as compared with pods and FAP capsules, and the kinetic of extraction is slower than CGA. The extraction profile of melanoidins and browning fitted better with the antioxidant capacity than CGA and total solids profile. Melanoidin populations were obtained according to ethanol solubility. Total melanoidin content and the ratio between melanoidin populations did not change during extraction volume for espresso coffee. Melanoidin populations soluble at 75% ethanol showed the highest antioxidant activity. However, melanoidins with higher antioxidant activity are extracted at higher volumes. This investigation could make possible the adjustment of the technological requirements of espresso coffeemakers to produce an espresso coffee with high levels of beneficial compounds.
... botanical kind of the beans, roasting degree, and particle size distribution) and process variables (i.e. extraction time, flow rate, temperature and water pressure) on the physicochemical attributes and sensory profile of espresso brews have been widely studied, such as by Andueza et al. (2002Andueza et al. ( , 2003Andueza et al. ( , 2007; Caprioli et al. (2012); Gloess et al. (2013); Lindinger et al. (2008); Maeztu et al. (2001) and Parenti et al. (2014). Although relevant conclusions may be drawn from these studies (e.g. ...
... This is especially true when the role of hydrodynamics process variables is discussed; their dependency on other variables is subtle and is sometimes neglected. For example, Andueza et al. (2002) studied 'water pressure' as a variable that may affect the quality of espresso brews, but they implicitly considered it to be independent of particle size distribution, packed bed structure, and flow rate. ...
Article
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In an espresso-style extraction hot water (90±5 °C) is driven through a coffee packed bed by a pressure gradient to extract soluble material from the coffee matrix. Permeability is a key parameter affecting extraction as it determines the flow rate through the bed and hence brewing and residence time. This may alter bed-to-cup mass transfer and therefore impact brew quality.In this work a methodology that will allow estimation of the permeability of coffee packed beds in steady-state was developed. Fitting measured flow rate – pressure drop data to Darcy’s law resulted in permeability values in the range of 10-13-10-14 m2. Disagreement between the experimental and theoretical permeability, as estimated from dry measurements of particle size distribution and Kozeny-Carman equation, was found. Bed consolidation may have a larger effect on the packing structure than the mere decrease in bed bulk porosity. The Kozeny-Carman equation, corrected with a porosity-dependent tortuosity according to a power law, gave a good fit of the data
... In the espresso brewing method, a pressure range of 7-9 bar and a temperature of 92°C is ideal for the most efficient extraction of some bioactive compounds such as caffeine, trigonelline, and nicotinic acid (Caprioli et al., 2014). Coffee beverages brewed using 9 bar pressure, have been described as having high foam consistency and aroma intensity, with few negative flavour notes (Andueza, Maeztu, Dean, & Cid, 2002;Caprioli et al., 2012). Increased pressure (up to 11 bar) can increase the viscosity, body intensity, and odour intensity. ...
... Increased pressure (up to 11 bar) can increase the viscosity, body intensity, and odour intensity. However, these coffee brews have lower consumer acceptance (Andueza et al., 2002). Other studies show that 11 bar of pressure increases VOCs extraction over the entire extraction time (25 s), with significantly higher intensities during the last 10 s of extraction (Sánchez-López et al., 2016). ...
Article
Background The physicochemical characteristics and flavour of coffee are related to the volatile and non-volatile compounds produced during roasting, which reach the coffee cup upon brewing. Scope and approach This review focuses on interpreting the contribution that various parameters have during the coffee extraction process (coffee brewing). Coffee brewing methods and their extraction parameters were analysed in terms of phenomenological explanations and their effect on the physicochemical and flavour characteristics of brewed coffee. Key findings and conclusions Many brewing methods have been developed to achieve a myriad of coffee flavour characteristics. Although several well-known brewing techniques have been adopted in the coffee industry, little associated relevant scientific data is available. Overall, these methods vary by extraction pressure, coffee/water ratio, water quality, contact time, particle size distribution, and temperature. An overview shows that all these factors modify the extraction of bioactive and volatile compounds that affect the flavour profile of the beverage. However, more in-depth explanation of the mass and energy transport phenomena would be useful to improve the understanding of the relationship between extraction variables and coffee flavour. Thus, phenomenological explanations are included to impart a better understanding of physicochemical and flavour changes in coffee beverages. Additionally, several gaps in knowledge relating to the extraction process are identified; and new trends in coffee extraction, including the cold brew method, are also discussed.
... The coffee parameters such as roast profile and granulometry have to be optimised with respect to the extraction parameters such as pressure and coffee-to-water ratio, water minerality and temperature. Some studies have investigated the impact of extraction temperature and pressure on the final in-cup quality (Albanese, Matteo, Poiana, & Spagnamusso, 2009;Andueza et al., 2002Andueza et al., , 2003Caprioli et al., 2012), or alternatively different extraction methods or tools were compared (Gloess et al., 2013;Parenti et al., 2014). Overall, these studies show that every extraction method has its own characteristics and needs to be fine-tuned in accordance with all previous steps in the coffee production chain in order to bring the desired result in the cup. ...
... The observed numeric values of the slope a/b are characteristic for the extraction parameters of this study, but the correlation of the extraction kinetics with the polarity might be general for different extraction parameters. Extraction parameters such as water temperature, minerality or pressure, which were kept constant in this study, might influence the water affinity/solubility of an odorant and as such change the extraction kinetics and in-cup profile, as observed in previous studies (Albanese et al., 2009;Andueza et al., 2002Andueza et al., , 2003Caprioli et al., 2012). ...
Article
To obtain a cup of coffee with a balanced aroma, every step in the coffee production chain is crucial, including the final brew preparation, in order to achieve the optimal result in-cup. In this study, the role of the physico-chemical properties (volatility and polarity) of coffee odorants during extraction was investigated. The extraction kinetics of 20 key coffee odorants from a coffee bed were measured using quantitative in-cup aroma analysis. The kinetics differed depending on the coffee odorants properties. The extraction speed could be correlated with the odorants’ polarity. Higher polar components, such as 2,3-butanedione, were released much faster from the coffee bed as compared to lower polar ones such as β–damascenone. In contrast, the odorants’ volatility did not seem to play a major role. Due to the different kinetics of extraction of the coffee odorants, the in-cup aroma balance changed continuously as more water passed through the coffee bed.
... In recent years, there have been renewed efforts to understand aspects directly related to the brewing process. Andueza et al. (2002) evaluated the effect of different extraction pressures on the quality of espresso coffee as reflected in physicochemical and sensory characteristics, whereas Mateus et al. (2007) investigated the wetting dynamics of coffee particles. Albanese et al. (2009) focused on the extraction temperature and found that extraction can be considered as an isothermal process with a true extraction temperature lower than the water reservoir temperature. ...
... The machine provides a constant water pressure of 11 bars at the fluid outlet, which was measured by an empty portafilter equipped with a manometer. This value is in the range that is used in practice and it was also used in other academic works (Andueza et al., 2002;S anchez-L opez et al., 2016). ...
Article
We investigated the extraction kinetics of caffeine and trigonelline from espresso coffee prepared in a commercial machine under realistic process conditions with varying particle sizes and tamping pressures of the coffee powder. On the one hand, it was found that the particle size significantly affects the extraction kinetics with smaller particles leading to a higher extracted amount of caffeine and trigonelline per collected coffee mass. Tamping pressure, on the other hand, has no detectable effect. Furthermore, the total extracted coffee mass was found to influence coffee composition as measured by the trigonelline/caffeine ratio. All data were sampled in triplicates with a high time resolution using a newly constructed sampling device. Finally, we introduced a new reduced model that describes the measured data well and contains only physically meaningful parameters. This work provides detailed data for better understanding the extraction of nonvolatile water-soluble components from espresso coffee, thereby aiding model development and validation. The presented simplified model may also prove useful for other related applications.
... As shown in Figure 1, the water pressure in Aurelia (9 bar) is always higher than that in Leva EC machine. This value of 9 bar is reported to be the best extraction pressure condition for 5-CQA ( Andueza et al., 2002). Probably, in Leva EC machine, because of the previous considerations, the pressure parameter seems to be not highly influent for chlorogenic acid extraction. ...
Article
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p>Chlorogenic acids (CGA) are a group of phenolic acid derivatives, which are commonly found in coffee at concentrations reaching 0.1-0.2%. A method based on high performance liquid chromatography-diode array detector (HPLC-DAD) is proposed for the simultaneous determination of three chlorogenic acids, i.e. 3- O -caffeoylquinic acid (3-CQA), 5- O -caffeoylquinic acid (5-CQA) and 3,5-di-O-caffeoylquinic acid (3,5-diCQA), in time portions of espresso coffee. Two different espresso coffee machines working with different pressure and temperature curves, and two different blends (i.e. Arabica and Robusta) were used. The method presents good linearities (correlation coefficient greater than 0.99) and recoveries (in the range 67-99%) for the 3 chlorogenic acids. The concentration of total CGAs in a cup of Certified Italian Espresso ranged from 1522.5 to 2223.4 mg kg<sup>-1</sup> and CGA isomer contents were, in decreasing order, 5-CQA > 3-CQA > 3,5-diCQA. The concentration of total chlorogenic acids was higher in Espresso coffee (EC) prepared with Aurelia machine rather than with Leva; Arabica blend possessed higher level ot total chlorogenic acids than Robusta samples. </p
... Passing of hot water under pressure through a ground coffee cake is the key to prepare espresso. Several aspects of coffee brewing have been investigated mainly on the effect of quality, comprising the effect of grinding (Andueza, de Peña & Cid, 2003), influence of water pressure (Andueza et al., 2002), ratio of coffee/water (Andueza, Vila, de Peña, & Cid, 2007), extraction temperature (Andueza et al., 2003a;Andueza, de Peña and Cid, 2003b), brewing techniques (Gloess et al., 2013;López-Galilea, Fournier, Cid, & Guichard, 2006;Parenti et al., 2014), and different botanical varieties (Maeztu et al., 2001). In addition to these, some studies investigated brewing in the view of antioxidant capacity. ...
... It is known that, coffee type, roasting conditions and degree (Sanz et al., 2002), grinding and storage (Anese et al., 2006) strongly affect EC quality. Also, several studies have been carried out on the effect of the setting parameter on brew quality, for example water pressure (Andueza et al., 2002), water temperature (Andueza et al., 2003) and brew time (Ludwig et al., 2012). Hence, the brew could be considered as influenced by several factors and the overall quality of the EC is hardly predictable. ...
Article
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Espresso coffee is the most popular choice for Italian coffee consumers. It has been estimated that every day, in the world, over of 50 million of Espresso cups are taken. As a consequence of this success, a large number of devices to make Espresso have been developed. In this scenario, a new device has been recently developed and patented (Eu. Patent 06 023 798.9; US 2010/0034942 A1). This brew method, named “Caffè Firenze”, uses a sealed extraction chamber, where water and gas provides pressure higher than the other extraction methods. Three main parts compose the apparatus: the gas source, the extraction chamber and the heat exchanger. The gas source provides the pressured gas required to raise the pressure of the system. The extraction chamber is made with chrome-brass and accessorized with two heating glow plugs. Many are the factors affecting Espresso quality: it is known that, coffee type, roasting conditions and degree, grinding and storage strongly affect the obtained brew. Also, several studies have been carried out on the effect of the setting parameters on quality, for example water pressure, water temperature, and brew time. Among the characteristics that determine Espresso quality, the main attribute for the visual analysis is, without doubts, the foam, also called “crema”. Indeed, height, aspect, and persistency of foam are features much appreciates by consumers. Two distinguish Espresso foam parameters are the persistency and foam index. Equipping a commercial bar machine with the new designed extraction chamber makes feasible the comparison between the traditional way to brew Espresso and the new device. The comparison was made holding the previous mentioned conditions, and differences were evaluated in terms of physical parameters and aromatic profiles. Caffè Firenze shows pronounced differences compared with traditional Espresso in term of foam-related parameters. Also, the new extraction device produces coffees with higher values of body-related parameters, such density and viscosity. The two kinds of Espressos are perceived different at visual analysis and taste by a panel test.
... EC is conventionally brewed using bar machines (BM), which consist of a rotating pump, a heat exchanger and an extraction chamber (Illy et al., 2005). The water pressure provided by the pump strongly affects the physical and sensory properties of the brew (Andueza et al., 2002) and maximal EC quality seems to correspond to an optimal water pressure of nine bars. ECs prepared at higher pressure have negative sensorial qualities as they are excessively bitter, astringent and contain more key odorants. ...
Article
Several brewing techniques are used to make espresso coffee. Among them, the most widespread are bar machines and single-dose capsules, designed in large numbers because of their commercial popularity. As none of the current literature compares the effects of these different brewing techniques on espresso quality, this paper looks at two capsule methods and the traditional bar method. The methods were eval- uated on the basis of the physico-chemical parameters and aromatic profile of nine espresso coffees pre- pared using the different techniques. Our results showed that with the same batch of roasted coffee, the same water and the same operative settings, the three different techniques can be distinguished by a principal component analysis. Furthermore, in terms of product reproducibility, the best results are pro- vided by the two capsule systems.
... The presence and the intensity of each specific sensorial descriptor in a cup of espresso coffee is influenced by the botanical origin and roasting degree of the coffee, but the result is strongly affected by the physical condition that controls the percolation process (grinding grade, temperature and pressure of the water, and percolation time). All these variables influence the amount and the type of substances that are extracted during the percolation process under hot water conditioning the chemical, physical and sensorial properties of the EC Andueza et al., 2002;Illy & Viani 1995;Nunes & Coimbra 1998). Inside an espresso coffee cup it is possible to find two types of substances that can be classified as soluble and emulsifiable compounds. ...
Article
In this work the thermal profiles of five coffee pods (pure Arabica, pure Robusta, and Arabica Robusta blends: A20R80, A80R20, and A40R60) at 90, 100 and 110 °C are reported. Moreover the chemical–physical and sensorial properties of espresso coffee (EC) obtained from five different coffee pods were investigated. The analysis of the thermal profiles highlighted that the extraction process can be considered as an isothermal process because, after a starting phase, the recorded temperatures stayed around a mean temperature (Tm). In addition the Tm recorded for each extraction temperature was significantly lower than those set up by the controller. The chemical–physical parameters of EC samples increased proportionally with extraction temperature highlighting that the effectiveness of extraction process scales up with percolation temperature. The solid and caffeine contents of the EC samples extracted at 110 °C are related to an over extraction process. Principal Component Analysis (PCA) was applied to identify relationships and differences among EC samples. Pure Arabica and A80R20 EC samples at 100 and 110 °C have shown sensorial attributes typical for a fine espresso coffee.
... In this particular complex system, interfacial phenomena such as foam and emulsion formation and stabilisation are of crucial importance in contributing to the greater sensory satisfaction espresso coffee gives to the consumer when It has to be taken into account, that variations in the preparation variables (e.g. coffee blend, roasting, grinding, water temperature and pressure, percolation time and/or beverage volume, etc.) can dramatically alter the 'cup result' not only in terms of taste, flavour and mouthfeel (chemical composition) but also in terms of the characteristics of the different phases present in the beverage (foam, emulsion, suspension and solution) and then on the beverage physical properties (Andueza et al., 2002;Maetzu et al., 2001). In Fig. 1 it is possible to observe variations induced by preparation conditions (beverage volume/percolation time) on chemical composition. ...
Article
Espresso coffee world-wide success, besides being a phenomenon of fashion, seems to be based on the greater sensory satisfaction it gives to the consumer when compared with coffees prepared with other brewing methods. Conditions normally used in the espresso brewing technique enhance several surface tension-related phenomena such as foam and emulsion formation and stabilisation which strongly affects the organoleptic beverage properties. In spite of the relevant role played by surface tension in several quality characteristics of espresso coffee, little attention has been paid in its determination and its time-dependency has not yet been investigated.In the present work, experimental techniques such as maximum bubble pressure and pendant drop have been used to characterise in a wide time window the dynamic surface tension of air–espresso coffee beverage interface at two different temperatures. The experimental data show a remarkable decrease of the surface tension with time for beverages prepared by using pure arabica as well as pure robusta roasted coffee, with a profile dependent upon the coffee variety. This behaviour is definitely related to the presence of surface active components and is consistent with a system having good wetting properties for oral cavity surfaces. A possible role of some natural surface active chemical components, like lipids, on tensiometric behaviour is discussed.
... The range of total solids obtained for the base blends analysed was lower comparing to the bibliography (Andueza, de Peña, & Cid, 2003;Andueza et al., 2002;Andueza et al., 2003;Andueza, Vila, Paz de Peña, & Cid, 2007;López-Galilea, De Peña, & Cid, 2007;Maeztu et al., 2001), which, with the exception of López-Galilea et al. (2007), reported values ranging from 1.36 to 1.81 g per cup. However, the range of ground roasted coffee amount used in these literature reports (6.5-8.5 g) was higher comparing with the amount present in the capsules tested in this study (6 g). ...
Article
Single-dose coffee capsules system is a technology used to prepare espresso coffee which offers consumers the possibility to choose among several blends. However, the characterisation of espresso coffees extracted with these systems, namely regarding polysaccharides structures and melanoidin content, is scarce. In order to define a carbohydrate and melanoidin composition pattern for single-dose espresso coffee base blends, a range of 6 commercial espresso coffee blends were studied. In addition, a decaffeinated and a blend supplemented with plant natural extracts were also included. The base blends showed galactomannans as the predominant polysaccharides over arabinogalactans. The exception was the decaffeinated blend. The blend supplemented with natural plant extracts showed glucose-rich polysaccharides. The labelled intensity of coffee single-dose seems to be related with the unknown brown compounds of melanoidins, present in the high molecular weight material of the brews. A pattern could be obtained for single-dose espresso coffee base blends, presenting an average per cup of 1.21 g of total solids, 242 mg of soluble dietary fibre, constituted by 62 mg of galactomannans and 48 mg of arabinogalactans, and 123 mg of melanoidins. On average, 46% of espresso coffee low molecular weight compounds are adsorbed to the high molecular weight material, evidencing the importance of the adsorption/desorption phenomena for the properties of coffee dietary fibre.
... The process of EC extraction is continuously analysed and benchmarked with quantified data of compounds, fostering further investigations for the development and optimization of the brewing [10][11][12][13]. The extraction of chemical compounds, which directly associates with flavour and aroma of EC, occurs in the extraction chamber. ...
Article
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The instrumental equipment of an espresso coffee machine has a remarkable influence on the extraction of the espresso coffee (EC). This study aims to evaluate the effect of different perforated disc heights and filter baskets, two fundamental parts of the espresso coffee machine, on EC carbohydrates content and composition. Four different heights (4–7 mm) of perforated discs and two different filter baskets were used to prepare Italian style EC and evaluate the feasibility of lowering the amount of ground coffee while keeping the same quality of the standard Italian espresso. Arabica and Robusta coffee beans, with 12 and 14 g of roasted coffee powder, were used to prepare 40 mL of EC, split in two cups. The content of total solids, high molecular weight material and polysaccharides, such as galactomannans (GM) and arabinogalactans (AG), were compared. The results show that the increase of the height of perforated disc affected the extraction of the polysaccharides content in the cup, with a decrease of GM and AG. As a conclusion, the configuration of perforated disc height and the filter used was shown to modulate the chemical profile of EC brew, with impact on espresso coffee cup quality.
... The EC overall quality is affected by many factors related to coffee (variety, roasting conditions and storage conditions) [1,[3][4][5], to water composition [6] and to the parameters of the percolation (temperature and pressure of water, grinding grade, dose of coffee, coffee/water ratio, pressure on the upper surface of coffee cake, extraction time) [7][8][9][10]. ...
Article
Full-text available
Electronic senses were applied in order to evaluate the effect of brewing temperature on the sensorial properties of espresso coffees (ECs) produced by a bar machine of the latest generation able to work with constant, increasing and decreasing water temperature profiles. The obtained ECs were analyzed by e-nose, e-tongue and e-eye to depict their aroma and taste fingerprint and to evaluate the visual characteristics of foam. Physicochemical analyses were carried out to determine the extraction rate of typical EC components and to evaluate their antioxidant activity. The electronic devices coupled with multivariate statistical analysis demonstrated a good ability to discriminate and characterize coffee samples on the basis of their sensorial properties in relation to the brewing temperature. According to these results, electronic senses can be applied to assess the influence of the percolation parameters on the sensory attributes of ECs, thus resulting useful tools for the optimization of processing conditions.
... The comparison of espressos obtained by different common coffee makers such as capsules or automatic and semi-automatic coffeemakers was studied by Gloess et al. (2013) in terms of chemical analytical methods and sensory analysis. Andueza et al. (2002) studied the influence of water pressure on the quality of arabica espresso coffee. The same authors investigated the influence of extraction temperature in the quality of espressos obtained from different coffee varieties (Andueza et al., 2003b). ...
... El café espresso (CE) es una de las formas más habituales de consumir el café y su preparación ha sido estudiada por algunos autores, quienes mencionan que la calidad es afectada por diversos factores, entre ellos, el tostado del café que para Baggenstoss et al. (2008) es responsable de la sensación organoléptica principal Tesis Doctoral llamada aroma, ya que durante este proceso se han encontrado 800 compuestos volátiles de los cuales 30 han sido identificados para este atributo .Para Navarini & Rivetti (2010), la calidad del agua ejerce una influencia relevante en el aspecto visual del café principalmente en la crema y en su contenido iónico. La presión para Andueza et al. (2002) conduce a obtener un mayor contenido de odorantes claves relacionados con la frescura y el sabor afrutado, así como la consistencia de la crema en los CE preparados a 9 atm en comparación con los preparados a 7 atm. ...
Thesis
This thesis was devoted to the analysis and evaluation of statistical methods to assess the quality of the coffee. In this sense, a contribution to try to quantify and qualify the coffee quality through statistical techniques addressed from Bayesian statistics, multivariate and experimental design were given. The methods described in each of the studies carried out, show the relationship and the differences of the different techniques used. In the first study, the coffee index of quality of the coffee from the department of Valle del Cauca in Colombia was developed taking into account the organoleptic and agronomic characteristics using Bayesian factor analysis. A database with some missing values (missing values). containing different organoleptic tests and agronomic aspects of the crop was used in the analysis. For the treatment of the data it was necessary to use data imputation techniques (listwise or case deletion (CD) Hot deck (HD) and multiple imputation (MI) of which database product chosen multiple imputation (MI ), since this technique showed more goodness in relation to others. Finally, it was found for the first time, coffee index of quality using a multiple factor analysis of Bayesian character due to the nature of the data as possible and complex parameterization. This index reflected spatially coffee crop areas that are identified as areas that produce good quality coffee. Besides other analyzes of interest in relation to the variety, profit, certification and others were performed. In the second study, the quality of the espresso was determined by investigating the effect of extraction temperature on the physicochemical properties of espresso, using three types of Natural Robusta coffees (Type A), Natural Arabica (Type B) and washed Arabica (Type C) and three different temperature profiles: upward extraction temperature (88 - 93 °C), flat (90-90 ºC) and downstream (93-88 ºC) with the latest innovation machine XCELSIUS RANCILIO class 9 trademark. The experimental design statistical tool known as the ANOVA analysis of variance of two factors (type of coffee and temperature profile) was used. Analyses showed that the use of temperature profiles allows modifying, modulate, enhance or reduce the organoleptic descriptors of an espresso. Finally, in the third study, the discriminatory elements to characterize espresso using the three types of coffees and profiles or extraction temperature curves that were used in the previous study were identified. The physicochemical properties were determined and cup tests were performed through a tasting panel that yielded organoleptic descriptors for each CE. The statistical processing using the multivariate technique called principal component analysis (PCA) was performed to analyze and visualize possible correlations, and to allow the identification of trends in the quality and their relationship to physicochemical properties.
... The machine has been optimized following tests of the effects of different brewing settings (i.e., pressure and temperature) on the physical and chemical parameters of the resulting coffee [9]. Water temperature and pressure are recognized as being particularly important for the quality of traditional espresso [10]. Other studies have revealed the importance of overpressure during the extraction of specific compounds [11,12]. ...
Article
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(1) Background: Recently, a new espresso extraction method, Caffè Firenze, has been developed, which uses gas at operating pressures of 20 bar to obtain abundant, persistent foam. The experiment aimed to evaluate the effect of using six gases (air, argon, nitrogen, carbon dioxide, carbon/nitrogen mix, and nitrous oxide) on the foam and liquid coffee. (2) Methods: Foam volume, persistence, sugar retention time, color, and rheological properties were measured. Volatile organic compounds were also evaluated. Analyses were also carried out on the liquid coffee to determine caffeine and chlorogenic acid concentrations. (3) Results: The analysis of variance revealed significant differences between the gases for all parameters. Multivariate analysis identified three groups of gases: the first comprised air, N2, and Ar; the second CO2 and N2O; and the third comprised samples extracted with CO2/N2 mix. (4) Conclusions: The choice of gas significantly influences the drink’s chemical-physical characteristics and is fundamental for product diversification.
... There are a lot of researches on the aroma element of coffee I)ll. Moreover, the general filter extraction method 3 l, the espresso extraction method 4 ) and the supercritical extraction method using carbon dioxide S) was tried for the efficient extraction. It is known that the underwater shock wave destroys the cell wall of the plant 6 l . ...
Article
The coffee beverage widely liked all over the world as articles of taste is extracted from roasted and milled coffee beans. The aroma with volatility compounds is a feature of coffee. A lot of extraction methods of coffee were researched. In this research, the underwater shock waveloading was tried to the roasted coffee bean to improve the extraction efficiency. The coffee extracted from the hot water by the filter method after the underwater shock wave loading compared the amounts of the extraction by the freeze-drying processing. In addition, extracted the volatility compounds were compared by the gas chromatography analysis. As a result, the change in the content of an excellent effect of the extraction and a volatility compound was confirmed.
... Todas estas variáveis sensoriais influenciam a quantidade e o tipo de substâncias que são extraídas durante o processo de percolação sob condicionamento de água quente a substância química do café (Andueza et al., 2002). ...
Article
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Objetivo: O objetivo deste estudo foi avaliar os efeitos moderadores do hedonismo nos fatores determinantes que influenciam na deciso de consumo de caf no Brasil.Mtodo: Foram avaliados 505 consumidores de 25 Estados brasileiros. Ao abrigo da anlise multivariada Regresso Linear Mltipla.Originalidade/Relevncia: As motivaes para o consumo de caf diferem entre os consumidores. Algumas motivaes hednicas so apresentadas na literatura, e exercem o papel de moderadoras nas relaes entre fatores ambientais fsicos onde h o consumo de caf, e fenmenos cognitivos durante o seu consumo. No entanto, ainda permanecem desconhecidas como as motivaes hednicas podem exercer impacto de moderao nas relaes do ambiente fsico e evocaes cognitivas versus o consumo do caf.Resultados: Os resultados fornecem evidncias empricas de que os fatores motivacionais do ambiente fsico e das evocaes cognitivas no so suficientes para compreender o consumo de caf.Contribuies Tericas/Metodolgicas: Este estudo apresenta um avano na literatura ao estudar o efeito de moderao hednicas nas relaes testadas, revela que o consumo de caf no ocorre por questes utilitrias, mas sim pela importncia e satisfao, no atendimento de diferentes sentidos multissensoriais como: prazer, excitao, diverso entre outros fenmenos hednicos.
... Espresso is a coffee beverage that is usually drunk immediately after brewing and without the addition of milk, which may lower its temperature [14]. Influences on the quality of espresso include the coffee variety (Coffea arabica or C. canephora) as well as its quality (e.g., defects, origin, etc.), the coffee/water ratio, the water pressure, or grinding grade [15][16][17]. For the extraction of espresso, the water temperature (brewing temperature) had the most significant influence. ...
Article
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Very hot (>65 °C) beverages such as espresso have been evaluated by the International Agency for Research on Cancer (IARC) as probably carcinogenic to humans. For this reason, research into lowering beverage temperature without compromising its quality or taste is important. For espresso, one obvious possibility consists in lowering the brewing temperature. In two sensory trials using the ISO 4120:2004 triangle test methodology, brewing temperatures of 80 °C vs. 128 °C and 80 °C vs. 93 °C were compared. Most tasters were unable to distinguish between 80 °C and 93 °C. The results of these pilot experiments prove the possibility of decreasing the health hazards of very hot beverages by lower brewing temperatures.
... Among these, the extraction pressure has the main influence on the acquired flavor profile of an espresso because it is also a dependent variable with respect to the permeability of coffee beds (Corrochano, 2015). A research conducted by Andueza et al., (2002) concentrated on the effect of water pressure in the physicochemical, sensory characteristics, and essential odorants of Arabica espresso. However scientific studies are still lacking to substantiate seeming impact of such key variables on cup quality. ...
Article
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Studies regarding particle size distribution, particularly in espressos are surprisingly few. Particle size distribution (PSD) is a plot that displays the average diameter versus percentage volume of the particles present in a sample. With increased awareness amongst coffee drinkers, a study aiming to report the effects of different pressure on particle size distribution of espresso from four different coffee blends was conducted. The method involved pulling of espresso shots at 7, 9, and 11 bar (or atm) from different coffee blends labeled as MA, CO, AL, and MO. Laser diffraction analysis showed different particle size groupings for each set of extraction pressure. Fine particles are within 1.20 to 28.70 µm. The most abundant particle size is centered at 185.4 µm. The particle size distribution of coffee blends composed of 100% Arabica coffee (AL and MO) but sourced from different locations, showed four similar modes or size ranges centered at 3.523, 13.005, 28.70, and 185.4 µm regardless of the extraction pressure or the coffee source. On the other hand, the coffee blends composed of different ratios of Arabica and Robusta (MA and CO) showed different modes depending on the pressure. This indicates the potential of PSD for characterizing the purity of a coffee blend. The particle size distribution can also give insights as to the sensory attributes of the espresso coffee.
... Several works study the effect of different technical conditions on the final espresso quality. Authors in [6] study the influence of water pressure and classify coffee prepared at three different pressure levels exploiting Principal Components Analysis (PCA) and Discriminant Analysis (DA). The influence of pressure has also been studied in combination with the extraction temperature, and the analysis showed that the temperature and pressure settings from domain-expert guidelines (i.e., 92 • C and 9 bar) are close to the ones needed to obtain the best quality espresso coffee [7]. ...
Article
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Coffee is among the most popular beverages in many cities all over the world, being both at the core of the busiest shops and a long-standing tradition of recreational and social value for many people. Among the many coffee variants, espresso attracts the interest of different stakeholders: from citizens consuming espresso around the city, to local business activities, coffee-machine vendors and international coffee industries. The quality of espresso is one of the most discussed and investigated issues. So far, it has been addressed by means of human experts, electronic noses, and chemical approaches. The current work, instead, proposes a data-driven approach exploiting association rule mining. We analyze a real-world dataset of espresso brewing by professional coffee-making machines, and extract all correlations among external quality-influencing variables and actual metrics determining the quality of the espresso. Thanks to the application of association rule mining, a powerful data-driven exhaustive and explainable approach, results are expressed in the form of human-readable rules combining the variables of interest, such as the grinder settings, the extraction time, and the dose amount. Novel insights from real-world coffee extractions collected on the field are presented, together with a data-driven approach, able to uncover insights into the espresso quality and its impact on both the life of consumers and the choices of coffee-making industries.
... The attributes were measured on an unstructured scale of ten centimeters in length (Fig. 2), with intensity identifications at one centimeter of the left and right extremities (Andueza et al., 2002). ...
... They found that the combination between three temperatures (75, 80, and 85°C) and two machine pressures (15 and 20 atm) not influenced the caffeine content of the coffee samples, showing an average value of 2.25 mg/mL. These data well agree with Andueza et al. [121] who tested three water pressures (7, 9, and 11 atm) on caffeine content of espresso coffee showing a mean value of 2.04 mg/mL. On the other hand, Salamanca et al. [122] proved that by applying a gradient of temperature to prepare an espresso cup across different varieties of roasted coffee, an increase or decrease of some chemical compounds was highlighted, among these the caffeine. ...
Chapter
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About 80–90% of the adults are regular consumers of coffee brews. Its consumption has positive effect on energy expenditure, power of muscle, while over consumption has negative effects widely debated. Across geographical areas, coffee brews may notably change when preparing Espresso, American, French, Turkish, etc. This chapter reviewed the phases able to affect the amount of caffeine in cup. Three most important areas will be addressed: (1) coffee varieties and environment; (2) coffee processing operations; (3) brewing methods extraction variables. What arises from the state of art is that, although there is a significant agreement on the effect of each critical variable on caffeine extraction , there is also a great difficulty to precisely know how much caffeine is in a coffee cup, although this is the most important information for the consumers. The number of affecting variables is very high, and some of them are inversely related with caffeine content (brewing time and brew volume), while others exhibit a direct relationship (grinding level, dose, and tamping). Finally, some variables under the control of barista rarely are accurately reproduced during brewing. For instance, it was found that the caffeine content in a Starbuck's coffee cup during different days varied significantly.
... It is known that, coffee type, roasting conditions and degree (Sanz et al., 2002), grinding and storage (Anese et al., 2006) strongly affect EC quality. Also, several studies have been carried out on the effect of the setting parameter on brew quality, for example water pressure (Andueza et al., 2002), water temperature (Andueza et al., 2003) and brew time (Ludwig et al., 2012). Hence, the brew could be considered as influenced by several factors and the overall quality of the EC is hardly predictable. ...
Article
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Espresso coffee is the most popular choice for Italian coffee consumers. It has been estimated that every day, in the world, over of 50 million of Espresso cups are taken. As a consequence of this success, a large number of devices to make Espresso have been developed. In this scenario, a new device has been recently developed and patented (Eu. Patent 06 023 798.9; US 2010/0034942 A1). This brew method, named “Caffè Firenze”, uses a sealed extraction chamber, where water and gas provides pressure higher than the other extraction methods. Three main parts compose the apparatus: the gas source, the extraction chamber and the heat exchanger. The gas source provides the pressured gas required to raise the pressure of the system. The extraction chamber is made with chrome-brass and accessorized with two heating glow plugs. Many are the factors affecting Espresso quality: it is known that, coffee type, roasting conditions and degree, grinding and storage strongly affect the obtained brew. Also, several studies have been carried out on the effect of the setting parameters on quality, for example water pressure, water temperature, and brew time. Among the characteristics that determine Espresso quality, the main attribute for the visual analysis is, without doubts, the foam, also called “crema”. Indeed, height, aspect, and persistency of foam are features much appreciates by consumers. Two distinguish Espresso foam parameters are the persistency and foam index. Equipping a commercial bar machine with the new designed extraction chamber makes feasible the comparison between the traditional way to brew Espresso and the new device. The comparison was made holding the previous mentioned conditions, and differences were evaluated in terms of physical parameters and aromatic profiles. Caffè Firenze shows pronounced differences compared with traditional Espresso in term of foam-related parameters. Also, the new extraction device produces coffees with higher values of body-related parameters, such density and viscosity. The two kinds of Espressos are perceived different at visual analysis and taste by a panel test.
... In the case of espresso brewing method, also the physico-chemical properties of the beverage can result to be altered by changing only one preparation parameter. Recently, for instance, the influence of water pressure (Andueza et al., 2002), extraction temperature (Andueza et al., 2003) and percolation time (Navarini, Ferrari, Suggi Liverani, Liggieri, & Ravera, 2004) were reported. ...
Article
The coffee brewing technique enhances several surface phenomena such as foam and emulsion formation and stabilisation.Recently the authors have been investigated the possibility to study the different contribution of the components of commercially available coffees well known as arabica and robusta.In the present work, dynamic experimental techniques such as maximum bubble pressure and contact angle have been used to characterise the air- coffee beverage interface at two different temperatures (20°C and 37°C).Different coffee-based beverage have been investigated ranging from espresso to soluble coffee.Beverage samples at different brewing times and methods have been prepared following standard procedures by using commercially relevant varieties and products. The role of the chemical components on tensiometric behaviour of the beverage is discussed.This behaviour is definitely related to the good wetting properties of the beverage on oral mucosa.
Article
Coffee beverages may be obtained using several extraction methods, among which espresso coffee (EC) represents now a worldwide adopted system. Recent advances in coffee grinding equipment allow today to achieve a detailed control of granulometric distribution, and the grinding process is an essential step of coffee production cycle both for the aromatic profile composition and for the chemical properties of the beverage (Severini, 2015). The comminution process consists of the breaking down particles into smaller fragments; as well-known, its main objective is to increase the overall particle surface area exposed to water leading to a more efficient extraction of soluble substances (Illy, 2005a). Basically, the coffee brewing process includes two steps: a washing phase concerning the snapshot dissolution of free solubles at the particle surface followed by diffusion phase of solubles within the porous particles (Spiro 1992, Baggenstoss 2008). The variability in particle size distribution on the quality of EC has been studied by various authors. Severini et al. has tackled the influence of the grinding level on the aromatic profiles and chemical attributes (percolation time, caffeine content, pH and titratable acidity) as a consequence of changes in the microstructural properties of the coffee cake. Generally speaking such results would imply that the final effect in terms of aromatic compounds extraction follows a monotonic law respect to granulometric size. This result is true in an average sense but it cannot be given for granted for any aromatic compounds if we refine the resolution of granulometric class. The reasons for which some aromatic compounds do not follow the supposed trend (the lower the grain size, the higher the aromatic compound content) can be most probably related to the internal distribution of precursors and to the different non-isotropic roasting grade of the bean, where the external part undergoes to an increased thermal load. This will change at the same time the kinetics and formation of aromatic compounds, and the mechanical properties as well, strictly correlated to the way the bean is crashed during the grinding phase and consequently to the granulometric distribution of different parts of the coffee bean. Results presented in this work allow to correlate choices in terms of granulometric distribution to characteristics aromatic compounds, in order to enhance specific flavors in espresso coffee.
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Este livro, adoptando uma perspectiva didáctica, procura de forma integrada abordar alguns aspectos ligados ao cafeeiro e ao café enquanto bebida. No seguimento de aspectos introdutórios associados à origem do cafeeiro e da bebida do café, equaciona-se a produção e o respectivo consumo a nível mundial; abordam-se aspectos taxonómicos, morfológicos e agronómicos; caracterizam-se opções tecnológicas associadas à industria do café; apontam-se ainda factores de qualidade associados ao consumo do café e desenvolve-se a respectiva composição química; interligam-se de forma sucinta interacções entre o café e a arte. Com uma linguagem que se pretende objectiva, esta obra também procura facilitar os processos de ensino e de aprendizagem de professores e alunos do Ensino Superior Universitário e Politécnico. Como corolário traduz ainda uma súmula de conhecimentos potencialmente interessantes para os leitores em geral."
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Espresso coffee (EC) is a common coffee preparation technique that nowadays is broadly widespread all over the globe. Its popularity is in part attributed to the intense aroma and pleasant flavor. Many researchers have studied and reviewed the aroma of the coffee, but there is a lack of specific review focused on EC aroma profile even if it is intensively investigated. Thus, the objective of the current review was to summarize the aroma profile of EC and how different preparation variables can affect EC flavor. Moreover, a collection of diverse analytical procedures for volatile analysis was also reported. The findings of this survey showed that the volatile fraction of EC is extremely complex, but just some compounds are responsible for the characteristic aroma of the coffee, such as some aldehyde, ketones, furanones, furans, sulfur compounds, pyrazines, etc. In addition, during preparation, some variables, e.g., temperature and pressure of water, granulometry of the coffee particle, and brew ratio, can also modify the aroma profile of this beverage, and therefore its quality. A better understanding of the aroma fraction of EC and how the preparation variables should be adjusted according to desired EC would assist coffee workers in obtaining a higher quality product.
Article
Using proton-transfer-reaction time-of-flight mass-spectrometry (PTR-ToF-MS), we investigated the extraction dynamic of 95 ion traces in real time (time resolution: 1 second) during espresso coffee preparation. Fifty-two of these ions were tentatively identified. This was achieved by on-line sampling of the volatile organic compounds (VOCs) in close vicinity to the coffee flow, at the exit of the extraction hose of the espresso machine (single serve capsules). Ten replicates of six different single serve coffee types were extracted to a final volume of between 30 - 110 mL, according to the recommended cup size of the respective coffee capsule (Ristretto, Espresso and Lungo), and analyzed. The results revealed considerable differences in the extraction kinetics between compounds, which led to a fast evolution of the volatile profiles in the extract flow and consequently to an evolution of the final aroma balance in the cup. Besides exploring the time-resolved extraction dynamics of VOCs, the dynamic data also allowed the coffees types (capsules) to be distinguished from one another. Both Hierarchical Cluster Analysis (HCA) and Principal Component Analysis (PCA) showed full separation between the coffees types. The methodology developed provides a fast and simple means of studying the extraction dynamics of VOCs and differentiating between different coffee types.
Article
In this study, the effects of particle size (222 to 1085 μm), packing amount (7.1 to 10.7 g), and brewing volume (113 to 226 mL) on physiochemical properties of the brew were investigated based on a single-serve coffee brewer. The results show that decreasing particle size could increase the extraction yield by about 63% without changing the extraction of acidic and phenolic compounds, implying finer grinds potentially could be used to reduce the use of coffee. Increasing packing amount had no effect on the extraction yield, but increased the concentration ratio of acidic to phenolic compounds, thus changing the flavor profile of the brew. > 80% of the soluble solids were extracted within the first 113 mL, while further brewing diluted the brew and introduced more bitter and astringent compounds. This study increased the understanding of single-serve brewing process, which is important to optimize brew quality and minimize production cost.
Article
Arabica coffee has been classified for trading according to the New York Board of Trade (NYBOT) green coffee classification. The aim of the present study is to evaluate the physiochemical and sensorial characteristics of coffees classified by NYBOT as NY2 (specialty coffee), NY3/4 and NY4/5 (commercial coffee). The density of green coffee was higher for the NY2 sample. The amount of total solids in brewed coffee increase as the green coffee grade decreased and the pH levels decreased as the coffee grade decreased. Descriptive analysis using a 15cm line scale was carried out by 12 trained panelists prepared by espresso coffee and consumer preference tests were carried out by 168 consumers. The NY2 sample had the highest fruity, acidity, sweetness and aftertaste characteristics. In addition, green, rio, sour and astringency characteristics increased as the coffee grade decreased. Acceptance of aroma, flavor, taste balance and overall were higher for the NY2 sample. In the consumer preference test, the NY2 and NY4/5 samples had a similar distribution, but consumers between the ages of 20 to 30 who like to drink brewed coffee more than instant coffee preferred the NY2 than sample over the NY3/4 sample. In conclusion, significant differences were observed among the three groups of green coffee classification in all physicochemical and sensory parameters.
Article
Grinding is an indispensible step in preparation of espresso coffee. The purpose of this study was to evaluate physicochemical and sensory characteristics of espresso according to the grinding grades of coffee beans. Specifically, physicochemical characteristics according to the grinding grades of coffee beans were tested based on foam index, persistence of foam, total solids, concentration, extraction yield, pH, viscosity, total soluble solid content and density. With regard to sensory characteristics, QDA were carried out by 10 trained panels. Persistence of foam, total solids, concentration, extraction, pH and viscosity in physicochemical test showed significant differences among the three categories of the samples. In other words, the finer the size of particles was, the higher value was, at the p=0.001 value. Meanwhile, the value of foam index and total soluble solid content to the grinding grades was the highest in 'fine', at the p=0.001 value. Tiger-skin effect in crema, an important attribute for excellent espresso coffee, was perceived by all of the panels in 'fine'. Also, intensity of flavor was perceived as to the strongest in 'fine'. Moreover, 'fine' had the sweetness to balance the acids and bitters. In conclusion, according to the grinding grades, it was identified that there were differences in the physicochemical and sensory characteristics. Furthermore, when the size of particles was 'fine', it brought to the most positive result.
Article
In the presented study the effects of key brewing parameters (temperature, holding time and storage conditions of coffee powder) on 12 alkylpyrazines in coffee beverages were investigated. The results show that the alkylpyrazine profiles of coffee beverages are similar to those of the coffee used. In total, 70–82% of the alkylpyrazines (113.3 ± 3.5 to 132.6 ± 0.6 mg/kg), depending on the brewing method, passed into beverages during the brewing process. At temperatures higher than 50 °C the alkylpyrazine contents of coffee beverages were almost independent of the brewing temperature. During a 30 min holding time at room temperature the alkylpyrazine contents of a freshly brewed cup of coffee decreased by about 10%. Furthermore, storing coffee in closed systems for up to 29 days at +4 °C, −20 °C or room temperature (+22 °C) had minor effects on the alkylpyrazine contents of beverages produced from the coffee. The results show that under customary conditions more than 70% of the alkylpyrazines present in ground coffee are transferred to beverages during the brewing process. Estimated total amounts of alkylpyrazines ingested by the consumer per cup of coffee beverage are in the milligram range, sufficient to have significant potential health effects.
Article
The single-dose coffee capsule is the most successful technology used to prepare espresso coffee (EC). However, the characterization of ECs extracted using this technology, regarding chlorogenic acids (CGAs) composition, antioxidant activity and stability during gastrointestinal digestion (GID), are still limited. The aim of this research work was: (i) to characterize the phenolic profile and antioxidant activity of 11 commercial ECs from single-dose capsule system and (ii) to evaluate the impact of the in vitro GID on the stability of CGAs. Within all the ECs analysed it was detected the presence of 4 caffeoylquinic acids (CQAs), 1 feruloylquinic acids, 2 caffeoylshikimic acids and 3 diCaffeoylquinic acids (di-CQAs). The major compound in all ECs was 5-CQA, followed by 4-CQA and 3-CQA. The di-CQAs were found in lower concentration than CQAs (4,5-diCQA>3,4-diCQA>3,5-diCQA). The total CQAs and diCQAs content of the ECs analyzed ranged from 1.86 ± 0.19 to 2.42 ± 0.28 and 0.26 ± 0.02 to 0.42 ± 0.06 mg/mL of EC, respectively. The high antioxidant activity of the ECs is related with the high CGAs concentration, which ranged from 4.92 ± 0.29 to 7.28 ± 0.25 mg AAE/mL of EC and from 6.13 ± 0.37 to 10.07 ± 0.17 mg TE/mL of EC for ABTS˚ and DPPH˚ methods, respectively. The principal component analysis showed that the coffee variety used in ECs preparation explained 74.8% of the results’ variation and that 6 of the total number of ECs were related with high CGAs contents and antioxidant activity. The GID induced a decrease in most CGAs, which had a direct impact on the antioxidant activity, therefore concerning EC ingestion the CGAs bioaccessible concentration decreased in comparison with a non-digested EC. Nevertheless, the CGAs concentration available after GID is still sufficiently high to exert antioxidant activity (measured in vitro) that may exert a potential beneficial effect on humans health.
Article
BACKGROUND In this study, the swelling behavior of roasted coffee particles in water and particularly its impact on particle diameter is examined by applying laser‐diffraction analysis and microscopy. Several potential influencing factors are investigated: initial particle size, roasting degree, and temperature. Additionally, the time dependency of swelling and particle shape is evaluated at two different temperatures. RESULTS We verify that particle erosion occurs—as observed by an increase of the fine particle fraction after wetting—and it is revealed that this effect is more pronounced with a rise in temperature. The total relative increase in particle size is determined as approximately 15% based on a broad range of different sized coffee grounds. It is demonstrated that the degree of swelling is independent of both the initial particle diameter and the roasting degree. The particle shape is found to be unaffected by swelling. This research reveals that swelling is initially quick, with 60–80% of the final steady‐state diameter being reached after 30 seconds and completed after four minutes of wetting, i.e., within the timescale of conventional coffee brewing methods. CONCLUSION This work provides a better understanding of the impact of wetting as part of the coffee brewing process, thus aiding the design, modeling, and optimization of coffee extraction. It clarifies the strong deviation of previous results on coffee‐particle swelling by considering particle erosion and degassing and provides a robust method for quantification. This article is protected by copyright. All rights reserved.
Chapter
From its legendary discovery in Abyssinia (today Ethiopia) to becoming one of the most consumed beverages in the world, coffee has captivated the enthusiasts for centuries due to its unique aroma and taste, as well as its effects as a stimulant in enhancing mental performance (e.g., alertness, concentration, attention). This article provides a brief overview on the production and processing of coffee, focusing on the Coffea arabica and Coffea canephora var. Robusta, also known as Arabica and Robusta, respectively. Differences in chemical compositions (e.g., lipid, sucrose, trigonelline, diterpenes, caffeine, chlorogenic acids) of bean variety contribute to desirable/undesirable sensory attributes, as well as the health implications of the final brew products. Roasting of green beans, which is typically carried out at 170–230 °C for 10–15 min, causes the degradations of polysaccharides, sugars, amino acids, chlorogenic acids, and so on. Concomitantly, a myriad of aroma volatiles and complex condensed products are formed, mainly due to Maillard reaction, Strecker degradation and pyrolytic reactions. The effects of roast time–temperature profiles on a number of key physicochemical phenomena are discussed, including changes in microstructural, formation of aroma species, development of color, and generation of CO2 during roasting. Optimal storage conditions and packaging are important in delaying product staling and to mitigate CO2 degassing issues. These aspects, along with other factors that affect the shelf-life of coffee, are discussed. Finally, a brief literature review on the health implications of coffee consumption is presented, highlighting the importance of several bioactive components (e.g., caffeine, chlorogenic acids, melanoidins, trigonelline, acrylamide, and diterpenes).
Article
Within the convention between the University of Bologna and Francesco Segafredo's P.A.C.S., an investigation of the quality of espresso coffee "in cup" was carried out in 58 shops located in various areas in Italy, with the aim to study the most important factors influencing its characteristics. Some analytical controls on immediate-extraction-coffee beverages, were made directly in the shops and others were made on samples taken in the shops and subsequently analyzed in the laboratory. The analyses showed that there is a great variability in the brews characteristics in the different shops, in particular as regards the soluble matter removed from the ground coffee and found in the extracted beverage. The acidity degree of the extracts was particularly constant, whereas the cream consistence was influenced by the length of time that the ground coffee remained in the "coffee-grinder-doser".
Article
The final quality of espresso coffee (EC) depends upon certain technical conditions, such as the extraction temperature used in preparing it. The aim of this work was to investigate the effects of water temperature (88, 92, 96 and 98 °C) on the final quality of three types of EC (Arabica, Robusta Natural blend and Robusta Torrefacto blend) in order to select the optimal temperature. Volatile compound (analysed by Static headspace gas chromatography/mass spectrometry) and sensory flavour profiles were the most relevant parameters, whereas physicochemical, taste and mouthfeel parameters were not very useful for selecting the water temperature. For Arabica and Robusta Natural blend ECs, 92 °C was the optimal water temperature. For Robusta Torrefacto blend EC the overall acceptability might lead to the selection of 88 °C as the ideal water temperature, but the high percentages of key odorants related to roasty and earthy/musty flavours and the ‘not hot enough’ perception dictated the selection of 92 °C in this case as well.© 2003 Society of Chemical Industry
Article
Two coffees of different botanical and geographical origins were used: Brazil coffee (dry-processed Arabica) and Uganda coffee (dry-processed robusta). The samples were roasted, and the foamability and foam stability of the espresso coffee were determined as a function of the degree of roast. Espresso coffees were characterized with regard to the amount of total solids, pH, fat, protein, and carbohydrate. The polymeric carbohydrates were precipitated with ethanol solutions (55 and 75% ethanol fractions), and the component monosaccharides were quantified by gas−liquid chromatography. A principal component analysis was applied to the chemical variables. This study showed that foamability of the espresso coffee increases with degree of roast and depends on the amount of protein in the infusion. Foamability as a function of the degree of roast does not differ significantly for the two coffees. Foam stability of espresso coffee as a function of degree of roast is related to the amount of galactomannan and arabinogalactan present and seems to be independent of the origin of the coffee despite the coffees having shown a different degree of roast for maximum foam stability. The degree of roast as a technological parameter does not allow an espresso coffee with maximum foamability and foam stability to be obtained at the same time. Keywords: Espresso coffee; degree of roast; foamability; foam stability; galactomannan; arabinogalactan; multivariate analysis; principal component analysis
Article
Chlorogenic acids (CGA) are a group of phenolic acid derivatives which are commonly found and differently distributed in higher plants. The CGA pattern can successfully be employed to characterize green and roasted coffees of different origins and qualities. This paper reports on the possibilities of characterizing green or roasted coffees by the CGA fraction through HPLC-W and principal component analysis (PCA) and comparing the results with those from sensory evaluation. The CGA fraction was prepared by submitting the Melitta extracts of green and roasted coffees to cleanup on a C-18 cartridge, and the 40/60 methanol/water fraction was then analyzed by a RP-C-18 column at 325 nm using a methanol/citrate-hydrochloric acid mobile phase in gradient elution. Examples concern the discrimination of coffees of the same quality but from different origins or plantations, discrimination of coffee blends of different compositions, and comparison with sensory evaluation.
Chapter
IntroductionExtraction Methods Beverage CharacterizationModified Coffee BeveragesReferences
Article
Equilibration time and temperature were the factors studied to choose the best conditions for analyzing volatiles in roasted ground Arabica coffee by a static headspace sampling extraction method. Three temperatures of equilibration were studied: 60, 80, and 90 degrees C. A larger quantity of volatile compounds was extracted at 90 degrees C than at 80 or 60 degrees C, although the same qualitative profile was found for each. The extraction of the volatile compounds was studied at seven different equilibration times: 30, 45, 60, 80, 100, 120, and 150 min. The best time of equilibration for headspace analysis of roasted ground Arabica coffee should be selected depending on the chemical class or compound studied. One hundred and twenty-two volatile compounds were identified, including 26 furans, 20 ketones, 20 pyrazines, 9 alcohols, 9 aldehydes, 8 esters, 6 pyrroles, 6 thiophenes, 4 sulfur compounds, 3 benzenic compounds, 2 phenolic compounds, 2 pyridines, 2 thiazoles, 1 oxazole, 1 lactone, 1 alkane, 1 alkene, and 1 acid.
Article
Three espresso coffee (EC) samples of different botanical varieties and types of roast were prepared in standard conditions using an experimental EC prototype: Arabica coffee, Robusta Natural blend, and Robusta Torrefacto blend (a special roast by adding sugar). The ECs were characterized with regard to the physical parameters, amount of total solids, total solids on filtrate, lipids, caffeine, trigonelline, and chlorogenic acids by HPLC, and sensory descriptive analysis related to foam appearance, taste, and mouthfeel. Principal component analysis (PCA) was applied to differentiate the EC samples. Arabica and Robusta samples were separated successfully by principal component 1 (55.3% of variance) including physicochemical and sensory parameters related to foam and taste of ECs. Torrefacto and Robusta Natural EC samples were separated by principal component 2 (20.7% of total variance) including mouthfeel and other attributes of color foam. Some interesting correlations among sensory and physicochemical variables were found. A very simple discriminate function was obtained by discriminate analysis allowing the classification of each EC sample into its respective group with a success rate of 100%.
Article
The aromas of three espresso coffee (EC) samples from different botanical varieties and types of roast (Arabica coffee, Robusta natural blend, and Robusta Torrefacto blend (special roast by adding sugar)) were studied by static headspace GC-MS and sensory flavor profile analysis. Seventy-seven compounds were identified in all of the EC samples. Among them, 13 key odorants have been quantified and correlated with their flavor notes by applying multivariate statistical methods. Some correlations have been found in the EC samples: some aldehydes with fruity flavors, diones with buttery flavors, and pyrazines with earthy/musty, roasty/burnt, and woody/papery flavors. By applying principal component analysis (PCA), Arabica and Robusta samples were separated successfully by principal component 1 (60.7% of variance), and Torrefacto and Natural Robusta EC samples were separated by principal component 2 (28.1% of total variance). With PCA, the aroma characterization of each EC sample could be observed. A very simple discriminant function using some key odorants was obtained by discriminant analysis, allowing the classification of each EC sample into its respective group with a success rate of 100%.
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Espresso Coffee: The Chemistry of Quality
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Influence of Extraction Temperature in the final quality of the Colombian Coffee cups. Proccedings of the 19th International Colloquium on the Chemistry of Coffee
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