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Influence of coffee/water ratio on the final quality of espresso coffee
Abstract
Espresso coffee is a polyphasic beverage in which the physico-chemical and sensory characteristics obviously depend on both the selection of ground roasted coffee and the technical conditions of the percolation process. The aim of this work was to evaluate the influence of the coffee/water ratio on the physico-chemical and sensory quality of espresso coffee. Furthermore, the influence of botanical varieties (Arabica and Robusta) and the type of roast (conventional and torrefacto) on the selection of coffee/water ratio was studied. The relationship between pH and the perception of acidity intensity is discussed in relation to the influence of the coffee/water ratio, type of coffee and roast. The optimisation of other technical parameters in previous studies seemed to minimise the influence of an increase in the coffee/water ratio on the extraction of soluble and solid compounds. In fact, only some sensory attributes, such as bitterness, astringency and burnt, acrid and earthy/musty flavours were proposed as relevant to the selection of 6.5 g 40 mL−1 or 7.5 g 40 mL−1 in conventional roasted coffees (Arabica 100% and Robusta blend), and 6.5 g 40 mL−1 in torrefacto roasted coffees. On the other hand, the addition of sugar during the roasting process in torrefacto roast coffees seemed to contribute to a higher generation of acids, melanoidins and other compounds by the Maillard reaction or caramelisation, which led us to select the lowest coffee/water ratio. Copyright © 2006 Society of Chemical Industry
... The preparation of coffee, in the solid-liquid extraction process, involves: (1) water absorption by ground coffee; (2) the soluble solids transferred into the hot water; and (3) separation of the extract from the exhausted solids. Many factors combine to modify and diversify the coffee beverage, including the contact time between the water and the ground coffee, the water temperature, and the pressure during extraction [3]. ...
... To standardize the tests, commercially available water was used. It presents the following composition: HCO 3 ...
... A descriptive statistical study using box plots (diameter of foam bubbles) and spider plots (sensory parameters) was conducted; an analysis of variance (ANOVA) was applied for inferential study. Tukey test, HSD (p < 0.05) (sensory parameters data) [3], (diameters of foam bubbles) was applied. Principal component analysis (PCA) was applied to identify patterns and structures on the sensory parameters: texture of crema, smell, sour, sweet, bitter, the balance, body, astringency, aroma, and persistence of aroma and the three coffee methods of extraction. ...
The coffee extraction methods modify the structure of the foam (when it is present) and the sensory profile of the beverage. In this research, three ways of extracting and two varieties of 100% Arabica were compared. Nineteen bars and fifteen bars were applied to the coffee thanks to the use of compatible capsules and machines. The method with the moka was considered, which acts at low pressures and does not allow the formation of foam (crema). In addition, the Brazil and Guatemala Arabica varieties were considered to understand the extent to which Arabica coffee can respond in structural and sensorial terms to the extraction techniques applied. The results show that 19-bar espresso coffees have a very stable crema with very small bubbles, which give a uniform and fine structure to the coffee crema. On the contrary, the pressure at 15 bars generates more unstable foams and bubbles that tend to be disproportionate, with more marked effects in the Brazil variety. The sensory profiles of the coffees respond to the extraction techniques applied. While the coffee extracted with the moka has sensory descriptors with rather low values, those obtained at 19 and 15 bars have much wider profiles. In conclusion, different pressure intensities to the coffee extraction affect the quality of crema and the solubilization of organoleptically active compounds.
... Several variables can modify in-cup coffee quality, including the contact time between the water and ground coffee, extraction time, the ground coffee/water ratio, water temperature and pressure (for espresso coffee), type of filter, and the boiling process. All of these factors play important roles in modifying caffeine content and other compounds (Andueza et al., 2003;Andueza, Vila, De Peña, & Cid, 2007;Gloess et al., 2013;Niseteo, Komes, Belščak-Cvitanović, Horžić, & Budeč, 2012). ...
... High temperature and pressure increase extraction yield and rate, seen in the difference between expresso and Moka coffees, and filtered brews (López-Galilea, . It is well-known that TDS % affects the sensory property described as 'body' (Gloess et al., 2013), and seems to be related to the coffee/water ratio (Andueza et al., 2007), and the brewing procedure (López-Galilea et al., 2007). Although the literature contains no data related to TDS, this factor is employed by baristas, and is recommended by SCAA to assess the correct degree of extraction. ...
... particle size and dose of ground coffee, tamping, water temperature and pressure, coffee/ water ratio, and the final volume of the drink) create considerable differences in bioactive compound extraction kinetics. Of these, one of the most important factors is the ratio of ground coffee to the final volume of water (Andueza et al., 2007). For this reason, the results of chemical analyses are presented in three ways: concentration (mg/mL), extraction efficiency (mg/g of ground coffee), and total bioactive content per cup (mg/cup), (Tables 3, 4, and 5 respectively). ...
The chemical composition of brewed coffee depends on numerous factors: the beans, post-harvest processing
and, finally, the extraction method. In recent decades, numerous coffee-based beverages, obtained using different
extraction techniques have entered the market. This study characterizes and compares eight extraction
coffee methods from a chemical-physical point of view, starting from the same raw material. Specifically, three
types of Espresso, Moka, French Press, and 3 filter coffee that for the first time are reported in the scientific
literature Cold Brew, V60, and Aeropress are compared.
Physical measurements included the quantification of total dissolved solids, density, pH, conductivity, and
viscosity. Chemical analyses identified 15 chlorogenic acids (CGAs): six caffeoylquinic acids, one p-
Coumaroylquinic acid, one Feruloylquinic Acid, four Caffeoylquinic lactones, and three Dicaffeoylquinic acids.
Maximum caffeine and CGA concentrations were found in Espresso coffees, while Moka and filtered coffees were
three to six times less concentrated. The classic Espresso method was most efficient for caffeine and CGA recovery,
with a yield almost double that of other methods. Per-cup caffeine and CGAs were higher in Cold Brew
than Espresso coffees, as a function of the volume of beverage, which ranged from 30 mL (for espresso) to
120 mL (for filtered coffees). In light of these results, it is not possible to establish how many cups of coffee can
be consumed per day without exceeding the recommended doses, since according to the applied brewing
method, the content of the bioactive substances varies considerably
... Considering the brew preparation at coffee shops, bar, or at home, several variables may modify the coffee quality in cup. The type of contact between water and coffee ground, the extraction time, the roasted-ground coffee/water mass ratio, the extract volume as well as water temperature, the vapor pressure in the case of Espresso coffee, filtration, and boiling process play important roles on the caffeine content of the beverage, as well as on functional and sensorial compounds [20,102,104,105,109,115,116]. First of all, the volume of the brew in cup is the variable exhibiting the wider variance mostly due to the personal appreciation. ...
... This variability has an important effect on the caffeine content of espresso coffee. Andueza et al. [116] highlighted that the caffeine content in EC cup is greatly affected by the quantity of coffee powder used. By preparing an EC of 40 mL, using 6.5, 7.5 and 8.5 g of ground coffee, the authors showed several differences in caffeine with values of 1.80, 1.88, and 2.21 mg/mL, respectively, when using doses of 100% Arabica coffee. ...
... Several studies highlighted that the increase in dose and/or grinding level, keeping constant the total volume of EC, determines an increase of caffeine concentration. Moreover, when the dose of ground coffee is higher, being the powder/water surface greater, the percolation pathway for hot water through the compact cake is more tortuous, increasing the brewing time and more aromatic and chemical compounds in coffee beverage [90,116]. ...
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.
... As the roasting progresses, temperature rise, moisture evaporation, volume increase, and dry matter decrease occur inside coffee beans, thereby roasting is one of the pivotal factors in determining coffee quality [7]. Coffee extraction refers to dissolving the soluble components of ground coffee beans in a liquid solvent [8]. The extracting procedure influences the composition of the final coffee extract. ...
... Espresso and drip extraction is the most commonly used method of coffee brewing [10]. The espresso method applies pressure above atmospheric pressure to the ground coffee beans [8]. In a drip method, coffee beans are ground into a powder, passing water through it and filtering the coffee extract simultaneously [10]. ...
Coffee roasting is the process of applying heat to green coffee beans to bring out flavors through chemical changes. This study aimed to investigate the effect of roasting degree on the antioxidant capacities of espresso and drip coffee extracted from Coffea arabica cv. Java in Laos. Green coffee beans were roasted under four conditions (Light-medium, Medium, Moderately dark, and Very dark), and espresso and drip coffee were extracted. The contents of total phenolics (TP), total flavonoids (TF), and chlorogenic acids (CGA) decreased as the roasting degree increased, whereas the caffeine content increased. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity was lower in the Medium, Moderately dark, and Very dark compared to the Light-medium. The ferric reducing antioxidant power (FRAP) was lower in the Very dark than the Light-medium, Medium, and Moderately dark. Principal component analysis showed that TP, TF, CGA, caffeine, DPPH radical scavenging activity, and FRAP distinguish coffee extracts with various roasting degrees. Therefore, it is concluded that roasting degree is a modifiable factor for the use of coffee as an antioxidant material in the food industry, and TF, TP, CGA, and caffeine contents, DPPH radical scavenging activity and FRAP are good indicators for determining the antioxidant capacity of coffee.
... However, there was no consistent trend in the content of aldehydes, which could suggest a potential variability in the quality and the perceived aroma from capsule-brewed ECs, especially from different brands [37]. Several aldehydes were reported in EC, such as acetaldehyde, propanal, 2-methylpropanal, 2-methylbutanal, and 3-methylbutanal [47,49,67,68]. ...
... Ketones were reported in the EC of arabica and robusta coffee beans [37,47,49]. Many studies reported the presence of 2,3-pentanedione and 2,3-butanedione in EC samples prepared from arabica and robusta natural blend coffees, while other ketones such as β-damascenone, 2-butanone, and 2,3-hexanedione, etc., were detected in arabica EC; the relative percentages of these ketones in arabica EC were significantly higher with respect to natural robusta blend EC [10,47,49,[67][68][69][70]. The foremost volatile molecule generated from the thermal degradation of furaneol is 2,3-pentanedione, while β-damascenone is formed by carotenoids. ...
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.
... Some studies successfully correlated the titratable acidity with sourness intensity (Fuse, Kusu, & Takamura, 1997). Conversely, other studies report no correlation between pH, titratable acidity, and perceived acidity (Andueza, Vila, Paz de Peña, & Cid, 2007;Gloess et al., 2013). There have been many efforts made to understand the relationship between pH, titratable acidity, and perceived acidity. ...
... So far, few studies have examined the direct effect of the coffee/water ratio on chemical and sensory characteristics of the coffee brew. Some studies performed in espresso brewing show that using a higher coffee/water ratio improves the extraction of caffeine, chlorogenic acid, and compounds related to bitterness and astringency (Andueza et al., 2007). Using 6.5-9.5 g of coffee in espresso brewing is related to increased diterpene concentration (31.92-42.53 ...
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.
... El café espresso (CE), es una de las mejores formas de consumir el café por que extrae sustancias aromáticas que provoca diferentes tipos de sensaciones organolépticas y que según Andueza et al. (2007) están asociadas a características fisicoquímicas. ...
... En la Figura 19, se muestran las densidades obtenidas para los tres tipos de café a diferentes perfiles de temperatura. Como se observa no hubo diferencias notables en ninguno de los cafés bajo las diferentes curvas de temperatura, situación que se corrobora con estudios realizados por Andueza et al. (2003aAndueza et al. ( , 2003bAndueza et al. ( , 2007. Masella et al. (2015), publicaron que la densidad viene afectada significativamente por la presión y no por la temperatura, lo que demuestra que los perfiles de temperatura no modifican la densidad. ...
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.
... Recent studies highlighted the importance of Espresso brewing conditions, including coffee blend and powder/water ratio, on the bioactive compounds observed in the cup. 11,14,48,51 Crozier et al. 52 reported that analysis of 20 Espresso cups from a unique coffee shop showed caffeine content between 51 and 322 mg per cup; a similar variability was also found for other bioactive compounds. ...
... As reported by several authors, statistically significant differences on aromatic profile and chemical compounds in coffee brews were found using different p/w ratios. 7,8,[10][11][12]51 For these reasons, we performed an additional series of experimental tests in which the brews were prepared using the Espresso coffee machine, but keeping constant the traditional coffee p/w ratios for American and Turkish coffee. The aim was to obtain coffee by the same extraction method, separating and highlighting only the effects of p/w ratio and temperature. ...
Background:
Depending on geographical origins and cultural traditions, different brewing procedures are used all over the world to prepare a coffee cup. In this work, we explored as three grinding levels of coffee powder and three coffee preparation methods such as by filtration (American), by boiling (Turkish) and by extraction under pressure (Espresso) affect healthy compounds and physicochemical attributes in coffee cup served to consumers.
Results:
the grinding level slightly affects the quality of coffees, while the preparation methods significantly influenced all in-cup attributes. When compared the content per cups, the American coffee presented higher values of antioxidant activity and total phenol content than Espresso and Turkish coffees. Caffeine content resulted of 316, 112 and 64 mg for American, Turkish and Espresso coffee cup, respectively.
Conclusions:
One American (316 mg), three Turkish (336 mg) and five Espresso (320 mg) coffee cups result in an amount of caffeine below the maximum daily consumption (400 mg/day) suggested by the European Food Safety Authority. The extraction method affects the intake of bioactive and antioxidant substances with specific properties.
... An increase in the extraction temperature, for example, leads to higher quantities of non-volatiles (i.e. total solids, caffeine, lipids) as well as higher quantities of some volatiles, such as pyrazines, in the final cup [16][17][18]. This may result in over-extraction and a coffee cup with negative flavor notes, such as woody, burnt or acrid flavors. ...
... 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. ...
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.
... 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). ...
... 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). This resulted in a higher coffee/water ratio which led to higher total solid amount in the brew (Andueza et al., 2007). The normalization of the results in g of total solids obtained per amount of coffee powder used for the preparation of the brew allowed to observe that the single-dose capsule system gives 0.17 to 0.21 g g −1 , excluding the supplemented blend (0.28 g g −1 ), which is in accordance with literature (0.15 to 0.24 g g −1 ). ...
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.
... affected not only by both the characteristics and the species of the green coffee beans, but also by the roasting process conditions (Andueza et al. 2007). The coffee roasting degree has been experimentally assessed using different analytical approaches, mainly based on off-line analysis of coffee batches, i.e. gathering this information only at the end of the process. ...
Variations occurring in coffee beans during roasting are ascribable to several chemical-physical phenomena: to quickly track the whole process and to ensure its reproducibility, a process analytical technology (PAT) approach is needed.
In this study, a method combining in-line Fourier transform near-infrared (FT-NIR) spectroscopy and chemometric modelling was investigated to get real-time and practical knowledge about the roasting effects on coffee’s chemical-physical composition. In-line spectra were acquired by inserting a NIR probe into a laboratory coffee roaster, running twenty-four roasting experiments, planned spanning different coffee species (Arabica and Robusta), four roasting temperature settings (TS1–TS4) and times (650–1580 s).
Multivariate curve resolution-alternate least squares (MCR-ALS) was used to model the chemical-physical changes occurring during the roasting process, and information about maximum rate, acceleration and deceleration of the process was obtained, also highlighting potential effects due to the different roasting temperatures and coffee varieties.
The proposed approach provides the groundwork for direct real-time implementation of rapid, non-invasive automated monitoring of the roasting process at industrial scale.
... Buratti et al. [21] stated that "the espresso coffee overall quality is affected by many factors related to coffee (variety, roasting conditions and storage conditions) [22][23][24][25], to water composition [26] 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) [27][28][29][30]". In this first eNose application example with complex aromas, these factors will be controlled by using an encapsulated espresso ground coffee, using soft mineral water to brew the coffee, and using a new semiautomatic coffee machine in order to guarantee similar brewing conditions that do not affect the aroma of the coffee. ...
This paper assesses a custom single-type electronic nose (eNose) applied to differentiate the complex aromas generated by the caffeinated and decaffeinated versions of one encapsulated espresso coffee mixture type. The eNose used is composed of 16 single-type (identical) metal–oxide semiconductor (MOX) gas sensors based on microelectromechanical system (MEMS). This eNose proposal takes advantage of the small but inherent sensing variability of MOX gas sensors in order to provide a multisensorial description of volatiles or aromas. Results have shown that the information provided with this eNose processed using LDA is able to successfully discriminate the complex aromas of one caffeinated and decaffeinated encapsulated espresso coffee type.
... The espresso brewing method differs drastically from cold or hot brew methods. In addition to high water temperature, espresso extraction is performed under high pressure using finely ground coffee [105][106][107][108]. Cruz et al. noted a high variability in the chemical composition of espresso SCGs and suggested that "the brewing method itself should be the main contributing factor to the compositional variance" [54]. ...
Nanotechnology has become increasingly important in modern society, and nanoparticles are routinely used in many areas of technology, industry, and commercial products. Many species of nanoparticle (NP) are typically synthesized using toxic or hazardous chemicals, making these methods less environmentally friendly. Consequently, there has been growing interest in green synthesis methods, which avoid unnecessary exposure to toxic chemicals and reduce harmful waste. Synthesis methods which utilize food waste products are particularly attractive because they add value and a secondary use for material which would otherwise be disposed of. Here, we show that spent coffee grounds (SCGs) that have already been used once in coffee brewing can be easily used to synthesize gold and silver NPs. SCGs derived from medium and dark roasts of the same bean source were acquired after brewing coffee by hot brew, cold brew, and espresso techniques. The total antioxidant activity (TAC) and total caffeoylquinic acid (CQA) of the aqueous SCG extracts were investigated, showing that hot brew SCGs had the highest CQA and TAC levels, while espresso SCGs had the lowest. SCG extract proved effective as a reducing agent in synthesizing gold and silver NPs regardless of roast or initial brew method.
... However, the acidity determined by sensory analysis was higher in 2 cycles (Figure 2). This result comes in agreement with other researchers who reported no correlation between titratable acidity and perceived acidity [7,25]. This difference may be explained by the fact that changes in coffee brew acidity are slight, and the most common methods to measure acidity (alkali titration) cannot detect small changes [7,26]. ...
The use of vacuum cycles for the cold extraction of coffee is a new process that leads to a significant reduction in process time of Cold Brew compared to conventional methods. This research aimed at specifying the necessary parameters for producing a consumer-accepted cold brew coffee by applying vacuum cycles. This was achieved by investigating the effect of the number of cycles and of the applied pressure (vacuum) on the physicochemical characteristics of the cold brew coffee, i.e., total dissolved solids (TDS%), pH, acidity, phenol and caffeine content and color. Furthermore, sensory evaluation took place by members of the Specialty Coffee Association of America (SCAA) to specify parameters such as coffee blend, coffee/water ratio, total water hardness and grind size and secondly to determine the optimal pressure and number of cycles for a tasty final beverage. The sensory and physiochemical characteristics of cold extraction coffee were investigated by Principal Component Analysis (PCA). It became evident that coffee extraction by applying two vacuum cycles at 205 mbar pressure produced the lowest intensity of physiochemical properties (caffeine, phenols , acidity, TDS% and pH), and the highest score of sensory characteristics (fragrance, body, acidity , flavor, balance, and aftertaste). Caffeine and phenol concentration of the optimal beverage were 26.66 ± 1.56 mg/g coffee and 23.36 ± 0.79 mg gallic acid/g coffee respectively. The physiochemical characteristics were also compared to a beverage of hot extraction of the same blend and ratio of coffee to water.
... After the preliminary analysis, fixed tamping pressure (≤10 lbs), 30 s percolation time, and water temperature (80-90°C) were used for concentrated cocoa drink preparation. Espresso made from Boncafe ground coffee served as a reference (Andueza et al., 2007). The targeted volume of concentrated cocoa drink was adjusted to 40 ml, as suggested by Andueza et al. (2003). ...
There is an increase in cocoa utilisation as an alternative to espresso coffee due to its lower caffeine content (17% less) than coffee. The polyphenols, theobromine is a good source of antioxidant contributed to the flavor and aroma in cocoa products. Different fat content and grinding levels were evaluated in producing a concentrated cocoa drink with a close resemblance to espresso coffee. Concentrated cocoa drink made of cocoa bean with 20% fat, grind at level 50 showed better caffeine content (3.31 µg/mL), theobromine content (34.26 µg/mL), antioxidant capacity (1726.3 μM TE), and TPC (193.57 mg/mL GAE). Five different classes of volatile compounds were detected from fresh‐brewed concentrated cocoa drinks responsible for the unique aroma properties, including alcohols, aldehyde, ketones, esters, acids, and pyrazines. These findings are significant to the cocoa industries, where the concentrated cocoa drink may act as an alternative cocoa drink with improved nutritional content.
... Based on the obtained results, authors concluded that coffee infusions prepared using cold and hot brewing technique are similar, taking into account the total concentration of deprotonated acid compounds; however, they differ in the concentration and possibly the complexity of protonated acids at the pH of extraction. No correlation between perceived acidity in the flavor of coffee brews and pH was observed by Gloess et al. [44] and Andueza et al. [45]. Furthermore, Gloess et al. [44] found no correlation between the pH and the titratable acidity of the coffee brews. ...
Coffee is one of the most often consumed beverages almost all over the world. The multiplicity of beans, as well as the methods and parameters used to brew, encourages the optimization of the brewing process. The study aimed to analyze the effect of roasting beans, the brewing technique, and its parameters (time and water temperature) on antioxidant activity (determined using several in vitro methods), total polyphenols, flavonoids, and caffeine content. The infusions of unroasted and roasted Arabica beans from Brazil, Colombia, India, Peru, and Rwanda were analyzed. In general, infusions prepared from roasted beans had higher antioxidant activity and the content of above-mentioned compounds. The hot brew method was used to obtain infusions with a higher antioxidant activity, while the cold brew with higher caffeine content. The phenolic compound content in infusions prepared using both techniques depended on the roasting process. Moreover, the bean’s origin, roasting process, and brewing technique had a significant effect on the tested properties, in contrary to brewing time and water temperature (below and above 90 °C), which had less impact. The results confirm the importance of coffee brewing optimization.
... The brewing time required is highly dependent on the brewing temperature and particle size to achieve the optimum extraction yield. For expresso brewing, in which hot water, high pressure and very fine grinds are involved, the extraction only takes about 25-30 s Andueza, Vila, de Pena, & Cid, 2007;Rao, 2008). On the other hand, for cold brewing the extraction can take up to 24 hr to achieve the ideal extraction (Fuller & Rao, 2017). ...
In this study, the extraction kinetics, based on total dissolved solid (TDS), at different temperatures (4, 23, 50, and 93°C) for different grind sizes (VMD = 139, 643, 1,450, 1,747 μm) were investigated. Coffee extraction proceeded in initial fast extraction stage followed by a significantly slower extraction stage, which correspond to the extraction from surfaces of broken cells and the extraction from intact coffee cells, respectively. Diffusion inside the coffee particle is a very slow process, so breaking the cells is a very efficient way to increase the mass transfer rate. In addition, the ultimate extraction yield increased with increasing brewing temperature and decreasing of particle size. The Weibull distribution, pseudo‐first order and pseudo‐second order model were fitted to the kinetics data, with high coefficients of determination (0.687–0.998), and low root mean square error (0.02–0.26%). Meanwhile, exponential equations were created to correlate the derived rate constants (1/α, k1, and k2) with brewing temperature and particle size to achieve the prediction of brewing extent (TDSt/TDSeqm) at different temperature‐particle size combinations.
Practical applications
This study investigated the kinetics of coffee extraction at different grind size and temperature conditions with the purposes to better understanding the cold and hot coffee brewing process, as well as to predict the coffee extraction. The findings in this study will have practical applications in three folds:
• Help manufacturers of coffee brew products (ready to drink or concentrate) to better design and control their coffee extraction process.
• Aid manufacturers of coffee extraction equipment and coffee brewers to improve their products
• Provide reference information for coffee store, barista, coffee enthusiast, and consumers to brewing a better cup of coffee
... As 43 different commercial capsule coffees were tested (Table 1) in this study, it was anticipated that flavour attributes would vary between products due to the potential use of different origins, varietals, processing methods, roast levels, grinds and blends. Nevertheless, body is particular as it represents a tactile sensation attributed to solids extracted from the coffee during brewing and becoming suspended in the beverage, making them quantifiable by measuring the TDS 24 . ...
The objective of this paper is to elucidate the variables that govern coffee extraction from single serve coffee capsules. The study was conducted on 43 Nespresso and Nespresso-compatible capsules of the same geometry, from all of which the coffee was extracted on the same machine. This allowed the link between a range of coffee and capsule (input) parameters with coffee brew (output) variables to be studied. It was demonstrated that the most efficient way to increase total dissolved solids in the brew is to use more coffee for extraction, and/or to grind the coffee more finely. However, grinding too finely can lead to excessive flow restriction. The most significant new insight from this study is the importance of the proportion of fines (particles smaller than 100 µm) regarding the capsule extraction dynamics. Capsules with a higher share of fines, for similar median particle size of the ground coffee, led to longer extraction times. General rules applicable for capsule coffee product development were established, although fine-tuning of parameters for successful capsule coffee extraction remains specific to production line and type of coffee.
... For example, the concentration for 2FMT is up to 5080 μg/kg in roasted coffee and only up to 39 μg/L in brewed coffee (Cheong et al., 2013;Semmelroch & Grosch, 1996). In terms of extraction, the amount of thiols and the sensory profile of the brewed coffee depends obviously on the amount on the initial powder, but also on this efficiency of the extraction it-self, including thiol polarity but also physical parameters of the brewing such as ratio powder/water, water temperature and pressure, contact time (Andueza et al., 2003;Andueza, Vila, Paz de Peña, & Cid, 2007;Caporaso, Genovese, Canela, Civitella, & Sacchi, 2014). ...
Volatile thiols are very strong-smelling molecules that can impact the aroma of numerous beverages. Several thiols and thiol precursors have been reported previously in different plants used as raw material for beverages, some of which are fermented. We focused on thiols in beverages and their release mechanisms from precursors during processing. Volatile thiols in beverages can be classified aslow molecular weight volatile thiols (e.g. H2S, methanethiol) which impact the smell negatively, and volatile thiols with higher boiling points that contribute positively to the aroma profile. The first part of this review is devoted to volatile thiols, without considering small malodorous molecules. The second part deals with thiol precursors and the different release mechanisms induced by processing (e.g. extraction, roasting or fermentation) and by the growing methods (e.g. viticulture), which can impact on amounts of thiols and their precursors.
... However, as expected, cold-brews with a higher C2WR were characterized by a stronger bitter taste and aftertaste and by higher intensities for flavor attributes such as mouthfeel, coffee ID, overall impact, longevity, roasted (a) (f), chocolate/dark chocolate (f), cocoa (a), fruity (a), fermented (a), smoky (f), ashy (f), woody (f), and fermented (f) [41]. These results support earlier research by Andueza et al. [130] that showed that espresso coffee (EC) brews with a high C2WR were more bitter and had higher intensities for burnt, roasted, acrid, and fermented flavors as compared to espresso coffee made with a low C2WR. ...
Flavor continues to be a driving force for coffee’s continued growth in the beverage market today. Studies have identified the sensory aspects and volatile and non-volatile compounds that characterize the flavor of different coffees. This review discusses aspects that influence coffee drinking and aspects such as environment, processing, and preparation that influence flavor. This summary of research studies employed sensory analysis (either descriptive and discrimination testing and or consumer testing) and chemical analysis to determine the impact aspects on coffee flavor.
... The foam volumes were measured immediately after the brewing operation using a 100 mL Pyrex-graduated cylinder (Andueza, Vila, de Pena, & Cid, 2007). The coffee, which had been brewed, was poured into the graduated cylinder and the first foam volume was recorded by reading the level from the cylinder at 97°C. ...
Turkish coffee is a special coffee due to its roasting, milling, brewing and storage processes. The roasting, milling, brewing and storage processes mainly affect the quality and physicochemical properties of Turkish coffee. The aim of this study is to determine; i) the optimum roasting method; oven (160, 180, 200 and 220 °C), microwave (350, 490, 700 W) or infrared (600, 1200 W), ii) the effects of different milling methods (cutter and hammer), iii) the effects of initial brewing temperature and water hardness, iv) the ideal brewing method (copper and electrical) and v) the ideal storage conditions. Microwave roasting at 350 W for 30 min and grinding with a cutter mill were found to be the better processes when compared to the others. Furthermore, the highest foam volume was obtained by using tap water at 4 °C and by brewing with a copper pot. The cold storing of Turkish coffee powder is a good storage condition to preserve the freshness; therefore, higher foam volume and stability were achieved under these conditions.
... which correspond to a specific quantile of the volume distribution, where the first index represents the respective quantile expressed in a percentage.This description must be distinguished from the De Brouckere mean diameter d4,3 which defines the volume moment mean of the particle size distribution. Based on the calculations using Equation (1) for the previously mentioned quantiles, the mean diameter increase and the respective standard deviation was calculated for different sized particles. ...
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.
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... 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]. The effect on quality is also studied with respect to the extraction temperature [8], water composition [9], roasting conditions [10] and also of coffee/water ratio, type of coffee and roast combined [11]. Proton-transfer-reaction time-of-flight MS (PTR-ToF-MS) is also exploited for monitoring changes in the volatile composition and PCA and hierarchical cluster analysis are applied to differentiate between coffee types [12]. ...
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.
... 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. ...
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.
... In the literature, the most studied hot extraction methods are the espresso and filtered coffee methods. Studies have been carried to evaluate the influence of the product formulation (e.g., bean botanical type, post-harvest processes, roasting degree) and brewing process variables (extraction time, flow rate, temperature, particle size distribution, and water pressure) on the physicochemical attributes and sensory profiles 5,8,9,[14][15][16] . ...
The effects of grinding (medium-coarse) and extraction time (14–22 h) on the physicochemical and sensorial properties of cold brew coffee produced using two types of Colombian specialty coffees (Huila and Nariño) were evaluated. Cold coffee brewed under coarse grinding and 22 h of extraction exhibited the highest values of total dissolved solids, extraction yield, pH, titratable acidity (TA), and total phenolic content. The type of coffee used mainly affected the TA and pH. All cold brew coffee samples had lower TA values than their hot counterparts. Nariño cold brew samples had higher TA values than those of Huila in all treatments evaluated. Higher scores were reported in the sensorial evaluation of cold brew coffee when prepared using the shortest time (14 h) and coarse grinding for both coffee types. These coffees were characterized by strong sweetness, fruity and floral flavours, medium bitterness and acidity, and a creamy body. Furans, pyrazines, ketones, aldehydes, pyrroles, esters, lactones, furanones, and phenols were detected as odour-active compounds. The findings of this study demonstrate that the particle size, contact time, and coffee type affect the physicochemical and sensorial characteristics of cold brew coffee, leading to cold brew coffees with different flavour profiles.
... However, many other variables may affect the properties of an Espresso coffee, such as the dose of coffee ground that affects the aroma and bioactive compounds of the brew [12]. Andueza et al. [13] found a caffeine content of 1.80, 1.88 and 2.21 mg/mL when using 6.5, 7.5 and 8.5 g of coffee ground. In addition, as reported from Severini et al. [8], the pressure on the top of coffee cake (i.e. ...
... For example, this approach has been taken with wine, 68−70 dried whey protein concentrate, 71 peanuts, 72,73 and coffee. 74 As descriptive analysis requires specific tasting facilities, panel training, and standards, it is impractical to employ in routine quality assurance programs. 14 However, performing descriptive analysis in combination with headspace volatile analysis during storage of almond samples might provide volatile indicators of important flavor attributes, which are more easily assessed in routine testing of almonds than are sensory attributes. ...
Understanding almond flavor, both in terms of sensory aspects and chemistry, is essential for processors to maintain almond quality and to correctly identify acceptable or unacceptable product. This overview of the sensory and chemical characteristics of almond flavor discusses raw and heat-processed almonds, the volatile compounds generated upon heating, the aroma qualities associated with various volatiles, and the use of descriptive sensory analysis for almonds. Flavor development and off-flavors in almonds due to rancidity is also explored. The review examines the existing methods used to assess common nonvolatile as well as volatile indicators of lipid oxidation in almonds, and the correlation of these indicators with consumer acceptance. Recent research on the relationship between volatile profile, rancidity indicators, and consumer acceptance is presented.
... pH. Work by Andueza et al. 47 and Gloess et al. 48 both report there is no correlation between pH and perceived acidity in the flavor of coffees. ...
The extraction kinetics and equilibrium concentrations of caffeine and 3-chlorogenic acid (3-CGA) in cold brew coffee were investigated by brewing four coffee samples (dark roast/medium grind, dark roast/coarse grind, medium roast/medium grind, medium roast/coarse grind) using cold and hot methods. 3-CGA and caffeine were found at higher concentrations in cold brew coffee made with medium roast coffees, rather than dark roast. The grind size did not impact 3-CGA and caffeine concentrations of cold brew samples significantly, indicating that the rate determining step in extraction for these compounds did not depend on surface area. Caffeine concentrations in cold brew coarse grind samples were substantially higher than their hot brew counterparts. 3-CGA concentrations and pH were comparable between cold and hot brews. This work suggests that the difference in acidity of cold brew coffee is likely not due to 3-CGA or caffeine concentrations considering that most acids in coffee are highly soluble and extract quickly. It was determined that caffeine and 3-CGA concentrations reached equilibrium according to first order kinetics between 6 and 7 hours in all cold brew samples instead of 10 to 24 hours outlined in typical cold brew methods.
... For example, considering the 2-cups filter holder, the total solids content obtained from the fine coffee ground was about of 336 mg/ mL, while values of ~74 and ~73 mg/mL were observed for fine-coarse and coarse coffee ground, respectively. Several works highlighted that the increase in the dose and/or of grinding level, maintaining constant the brew volume, determines a reduction in the pH and an increase in both total solids and caffeine content [9,45]. Moreover, several authors observed that the particle size of coffee powder is inversely related to the extraction of chemical compounds in EC samples [6,7,35] because when the porosity of coffee cake is reduced (with the fine coffee ground), the water/ solid surface contact area is greater, while the percolation pathway of water is more tortuous. ...
The Italian espresso coffee is the most aromatic coffee brew. Among the several variables affecting the physicochemical and sensorial attributes of the beverage, the use of different types of coffee filter holders was never studied. Electronic nose is a useful technique for the control of food and beverages because it combines the advantages of both instrumental and sensorial analyses. In this work, the influence of two filter holders, 1-cup or 2-cups, on the main chemical attributes and global aromatic profile of the espresso coffee samples, obtained in different extraction conditions, was studied. Any significant differences were not observed in the overall aromatic profile of espresso coffee brews by using the two types of filter holders, whereas the pH, titratable acidity, total solids and caffeine content were greatly affected by the type of filter holder.
... 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. ...
... This explains why extensive research has been conducted in the past to understand the impact of coffee processing and preparation parameters on chemical composition and related sensory properties (Andueza, Vila, Paz de Peña, & Cid, 2007;Charles et al., 2015;Lindinger et al., 2008;Navarini & Rivetti, 2010;Albanese, Di Matteo, Poiana, & Spagnamusso, 2009) as well as consumer preference (Cristovam, Russell, Paterson, & Reid, 2000). ...
The formation and stabilization of crema on espresso coffee are areas that have been well studied during the last 2 decades. In contrast, the contribution of the sensory perception of crema in the coffee consumption experience has not received a lot of attention. Crema being a key visual differentiator between espresso coffees, it may influence the overall sensory and hedonic experiences through the process of assimilation or contrast of visually induced expectations. The objective of this research was therefore to investigate the role of the expectation generated by crema visual cues on actual sensory and hedonic espresso coffee consumption experience. The study was designed to measure the impact of absence, presence and amount of crema on expectation for espresso coffee in liking, quality, overall taste intensity, bitterness and smoothness. Four espresso coffees with different amounts of crema were rated on each attribute by espresso coffee consumers in three evaluation conditions: visual condition (expectation induced by crema visual cues), in-mouth condition (espresso coffee tasting while participants were blindfolded), full condition (standard tasting). The aim of this procedure was to quantify the respective contribution of crema visual cues and in-mouth espresso coffee tasting to the overall espresso coffee experience. Results showed that espresso coffee without crema was expected to be moderately liked, low in quality and weakly smooth as compared to espresso coffee with crema. Such expectations negatively impacted hedonic and sensory in-mouth experience through assimilation effect. Change in crema amount also impacted consumers' expectation which in turn modulated hedonic and sensory experience for espresso coffee. For the first time, this study highlighted the key role of crema visual cues on espresso coffee consumption experience.
Coffee filters and drippers advertised with various functions such as balanced flavour, sweeter taste and plentiful coffee scene are popular options for hand‐brewed coffee lovers. This study investigated the flavour of filtered coffee brewed by various coffee filters including Hario V60 filter, Kalita filter, flannel cloth filter and stainless‐steel (screen) filter based on the physical and chemical properties of the beverages. The results showed that the extraction time of V60 and flannel cloth filter were shorter. Kalita filter offered longer extraction time and obtained the highest amount of chlorogenic acids than other drippers. In the volatile profiles of aroma compounds, flannel cloth and stainless‐steel filters obtained higher total volatile compounds that may due to less volatiles were absorbed by filter material compared with paper filters, V60 and Kalita. Combined physical and chemical data among four extraction methods, partial least squares‐discriminant analysis (PLS‐DA) was able to separate samples into approximate four clusters. 2‐Acetylfuran and 3‐methyl‐phenol were found fluctuated wildly among samples and would be important factors for the differentiation of pour‐over coffee. This study suggested that the four coffees brewed by different filters have their own characteristic aroma profiles and did show their differences based on the chemical compositions caused by dripping speed and the interactions with filters. Flavour characteristics of pour‐over coffee brewed through V60 dripper, Kalita dripper, flannel cloth filter and stainless‐steel filter were compared. V60 dripper and flannel cloth offered fast extraction. Kalita provided a stable flow rate and extracted more total solids and chlorogenic acids.
Turkish-style brewed coffee, i.e., ground coffee boiled in special pots, is one of the most consumed traditional beverages in Turkey given its unique and delicate flavor. In the current study, the effects of brewing in different pots (automatic coffee machine (ACM), stainless steel pot (SSP), and copper pot in hot sand (CPS) on the pyrazines, total phenolic content, and antioxidant activity in Turkish coffee were elucidated for the first time. Pyrazine compounds were carried out by the application of gas chromatography-mass spectrometry (GC-MS). A total of nine pyrazine compounds were detected in the samples. According to the results, the samples brewed in a copper pot in hot sand had the highest amount of pyrazines followed by SSP and ACM. 2-Methylpyrazine was found in abundance in all three samples while 2,5-dimethylpyrazine and 3-ethyl-2,5-dimethylpyrazine were the other substantial compounds. In contrast with the pyrazine formation in samples, ACM had a considerable amount of total phenolics and antioxidant activity followed by SSP and CPS. This may result from the less boiling time in ACM (around 90 seconds) which prevented the degradation of phenolics to an extent.
El café es una de las bebidas más consumidas en el mundo y su popularidad no está basada en su valor nutricional o sus potenciales beneficios a la salud, si no en su sabor placentero y las propiedades estimulantes de la cafeína. Esto es respaldado por las últimas estadísticas publicadas por la Organización Internacional del Café (ICO, por sus siglas en inglés) según la cual aproximadamente 1.4 billones de tazas de café son consumidas diariamente además del hecho de que la taza de consumo global se ha duplicado en los últimos 50 años por causa de la apertura de nuevos mercados. La amplia aceptación del café está ligada a sus propiedades sensoriales las cuales a su vez están fuertemente influenciadas por una cadena de eventos que inician desde la cosecha y las practicas postcosecha (i.e., fermentación, lavado, secado, tamizado, eliminación de granos defectuosos y almacenamiento), seguidas por el tueste, molido y empacado del producto para su posterior comercialización. No obstante, existen otros factores que también afectan las propiedades organolépticas de la bebida tales como, pero no limitado a: el pH y temperatura del agua, las mezclas realizadas antes o después del tueste, la especie y/o variedad de café, las adulteraciones, la incorporación de aditivos, el método de preparación de la bebida, el tipo de recipiente en el que se sirve la infusión, entre otros. El presente artículo presenta una breve descripción de los factores que afectan la calidad de la taza relacionados con el procesamiento del grano oro del café. Sin embargo, aunque los factores ya mencionados son tomados en consideración por los catadores, para fines comerciales, la calidad del café está y siempre estará en manos del consumidor. Después de todo la mejor prueba es cuando la persona lo prueba. Palabras clave: organoléptica, perfil de tueste, endotérmica, exotérmico, ma-croscópica, microscópica, reacción Maillard, caramelización.
Flavor instability of ready-to-drink (RTD) coffee during storage negatively impacts product quality. Untargeted liquid chromatography/mass spectrometry (LC/MS) analysis was applied to identify chemical compounds that degraded during storage and impacted the flavor attributes of RTD coffee. LC/MS chemical profiles of non-aged and aged coffee samples were modeled against the degree of difference sensory scores by orthogonal partial least squares with good fit (R2Y = 0.966) and predictive ability (Q2 = 0.960). The top five predictive chemical features were subsequently purified by off-line multidimensional Prep-LC, revealing ten coeluting chlorogenic acid lactones (CGLs) compounds that were identified by LC/MS and nuclear magnetic resonance (NMR). The concentrations of eight CGLs significantly decreased in the coffee during the 4-month storage. Sensory recombination testing revealed the degradation of 3-O-caffeoyl-ɣ-quinide and 4-O-caffeoyl-ɣ-quinide significantly impacted the flavor stability of RTD coffee at subthreshold concentrations.
Coffee contains a variety of organic acids (OAs) and chlorogenic acids (CGAs) that contribute to overall sensory properties. Large variations in preparation and measurement methodology across the literature complicate interpretation of general trends. Here, we perform a systematic review and meta-analysis of the published literature to elucidate the concentrations of OAs and CGAs in both Coffea arabica (arabica) and Coffea canephora (robusta), for both green coffee and roasted coffee at multiple roast levels. A total of 129 publications were found to report acid concentration measurements, yielding 8,634 distinct data points. Analysis of the full data set reveals several trends. First, roasted robusta has considerably more acidic compounds than arabica with 2 to 5 times as much total OAs, and much larger amounts of formic and acetic acid. As for CGAs, in both arabica and robusta 5-CQA is the major component, and progressive roasting decreases the concentration of all CGAs. The total amount of CGA present was more dependent on roast level than the type of coffee (arabica vs. robusta). Overall, this meta-analysis suggests that the increases in certain OAs with roast level might play more of a role in the sensory profile of dark roast coffees than previously suspected.
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.
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).
All coffee brews are prepared with roasted coffee and water, giving origin to espresso, instant, or filtered coffee, exhibiting distinct physicochemical properties, depending on the extraction conditions. The different relative content of compounds in the brews modulates coffee body, aroma, and colour. In this study it was hypothesized that a coffee infusion allows to obtain extracts that resemble espresso coffee (EC) physicochemical properties. Carbohydrates (content and composition) were the target compounds as they are organoleptically important for EC due to their association to foam stability and viscosity. The freeze-drying of the extracts allowed better dissolution properties than spray-drying. Instant coffee powders were obtained with chemical overall composition resembling espresso, although with lower lipids content. The extracts were able to produce the characteristic foam through CO2 injection or salts addition. Their redissolution at espresso concentration allowed a viscosity, foamability and volatile profile representative of an espresso coffee, opening new exploitation possibilities.
Drip brewed coffee is traditionally quantified in terms of its strength, also known as total dissolved solids (TDS), and its brewing yield, also known as percent extraction (PE). Early work in the 1950s yielded classifications of certain regimes of TDS and PE as “underdeveloped,” “bitter,” or “ideal,” with the modifiers “weak” or “strong” simply correlated with TDS. Although this standard is still widely used today, it omits a rich variety of sensory attributes perceptible in coffee. In this work, we used response surface methodology to evaluate the influence of TDS and PE on the sensory profile of drip brewed coffee. A representative wet‐washed Arabica coffee was roasted to three different levels (light, medium, or dark), with each roast then brewed to nine target brews that varied systematically by TDS and PE. Descriptive analysis found that 21 of the 30 evaluated attributes differed significantly across the brews for one or more experimental factors, yielding linear or second‐order response surfaces versus TDS and PE. Seven attributes exhibited a significant response surface for all three roast levels tested: burnt wood/ash flavor , citrus flavor , sourness , bitterness , sweetness , thickness , and flavor persistence . An additional seven attributes also showed a significant response surface fit across some but not all roasts. Importantly, sweetness exhibited an inverse correlation with TDS irrespective of roast, while dark chocolate flavor and blueberry flavor decreased with TDS for medium roast. These results provide new insight on how to optimize brewing conditions to achieve desired sensory profiles in drip brewed coffee.
Practical Application
This research provides guidance on how best to achieve specific flavor profiles in drip brewed coffee.
Recent years have seen a growing awareness of the need to reduce waste and protect the environment. During the preparation of a coffee beverage, large amounts of a solid residue known as spent coffee grounds (SCG) are produced.
This study investigates the recovery of phytochemicals from SCG. The aim is to estimate the effect of a wide number variables on the amount of caffeine and phytochemicals recovered with a green method for water-soluble compounds that does not require the use of organic solvents. In the first part, we use a Plackett–Burman design to estimate which extraction parameters have most influence on phytochemical recovery. In the second part, we test only the significant factors and caffeine and chlorogenic acids were quantified using HPLC-DAD.
The first part of the study showed that the temperature and the type of SCG can significantlyaffect the phytochemical recovery. In the second part, four temperatures and two types of SCG were tested and thehigher concentrations of caffeine and chlorogenic acids were found at 110 °C. Furthermore, a significant effect was found for type of SCG with significantly higher phytochemical recovery for the French Press compared to the Espresso method. The mild temperature, combined with the use of water as a solvent make the recovery system both green and low-cost.
Coffee infusion experiments were conducted to infer how operational variables (time, temperature, mass to volume ratio, and grinding) might affect the efficiency and/or selectivity of compounds extraction. Although the different variables have extensively been reported independently, to the best of our knowledge, no experimental design was yet delineated to study the simultaneous effect of variables in coffee composition. This study fulfills this gap by constructing surface models that reflect the responses in a wide-ranging design space. The freeze-dried extracts were compared regarding the overall yield of extraction, carbohydrate content and composition, caffeine, chlorogenic acid (5-CQA) content, color, and viscosity. Temperature was the major factor for coffee extracts differentiation, regarding both overall and carbohydrates yield and composition. The extraction process efficiency is more related to galactomannans extraction than arabinogalactans. Varying operational conditions, coffee extracts with distinct chemical properties are obtained from the same roasted coffee, broadening their applications in food formulations.
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This present work aimed to evaluate the encapsulation of bioactive compounds extracted from espresso spent coffee, applying the spray drying technique. The use of whey protein isolated (WPI) as wall material, and the combination with maltodextrin (MD), Arabic gum (AG) and inulin (IN) (1:1 proportion) to retain the bioactive compounds and antioxidant activity were also assessed. The contents of phenolic compounds, caffeine and chlorogenic acids were determined in order to evaluate the encapsulation efficiency of each treatment. Additional analyses for characterization of the samples were also performed. It was possible to obtain particles of spherical shape with no cracks on the surface. The use of WPI showed greater efficiency in the maintenance of the antioxidant activity measured by different methods. The encapsulates obtained carried and protected considerable amounts of antioxidants present in the coffee, which were extracted from processing wastes.
A study was taken up to evaluate the relationship between the sensory perceived acidity and instrumentally measured acidity in thirteen coffee samples representing the two major commercially cultivated coffee varieties viz., Coffea arabica (arabica coffee) and C.canephora (robusta coffee) in India. The acidity level in these coffee samples was assessed by three ways viz., organoleptic (sensory perceived) scoring, pH meter and titratable acidity. The results of this study revealed that acidity level assessed by the organoleptic scoring matched with the acidity level measured by pH meter and titratable assay method. Statistical analysis of these results indicated there was close correlation between sensory perceived acidity and instrumentally measured acidity as evidenced by the correlation coefficient (r 2) value ranging from 0.86 to 0.99.
A good cup of coffee is characterized by a subtle equilibrium of aroma, taste, and mouthfeel. The brewing step allows extracting the odorants and taste molecules from the roast and ground coffee into the consumer's cup. Various methods of preparation exist, based on origin, culture, and ultimately consumer preference. For each of these, several parameters play a role in delivering a beverage with a balanced flavor. This chapter aims to combine barista experience with a molecular understanding of what happens during extraction to broaden the insight into how the in-cup flavor can be modulated through extraction.
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.
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.
Coffee is undoubtedly one of the most complex of the more commonly encountered food commodities from the point of view of its chemistry. Not so much because the green coffee bean contains a wide range of different chemical compounds, but rather that these compounds react and interact at all stages of coffee processing to produce a final product (a cup of coffee) with an even greater diversity and complexity of structures. Our understanding of this complex mixture has been exacerbated by two major analytical problems, namely the extremely low levels at which some compounds are present, and yet will have sensory significance, and secondly that many of the interactions lead to the formation of high molecular weight polymeric material which is often very difficult to characterise structurally. Nonetheless, polymeric material may well contribute up to 50 % of a coffee brew and is important for aroma retention as well as physical properties. These analytical problems become readily apparent in a consideration of the nitrogenous components. Thus, for example, volatile nitrogen heterocyclic compounds may be present at the sub-ppb level, and the brown pigments or coloured matter present in coffee brew are mainly high molecular weight products of the browning reaction (melanoidins).
Quantitative Data on Organic Acids in Green CoffeeDetermination of Organic Acids in Roasted CoffeeAcid Formation MechanismsAcid Increase on StorageVolatile AcidsAcid Content and Sensory CharacteristicsReferences
twentytwo compounds, which had been revealed by dilution experiments as potent odorants, were quantified by stable isotope dilution assays in brews prepared fro roasted Arabica and Robusta coffees. Calculation of odor activity values (OAVs); ratio of concentration to odor threshold) indicated 2-furfurylthiol, 3-mecapto-3-methylbutyl formate, methanethiol, ß-damascenone, methylpropanal, 3-methylbutanal as the most potent odorants. However, the rankings of the OAV were different in the two coffee brews. Thextraction yields obtained during the preparation of the brews were determined for 17 odorants. Polar compounds /e.g. guaiacol, 4-hydroxy-2,5-dimethyl-3(2H)-furanone, 3-hydroxy-4,5-dimethyl-2(5H)-furanone, 2,3-butanedione) were extracted with higher yields (75-100 %); nonpolar compounds (e.g. ß-damascenone, 2-isobutyl-3-methoxypyrazine) gave yields of only 10-25%. The overall odor of the models containing the odorants in the concentation levels that had been found in the two brews was clearly coffee-like. The models reproduce the differences in the odor profiles of the two brews.
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
A method that differentiates between different roasted coffees and coffee beverages is described. Characterization is achieved by applying principal component analysis (PCA) to the chromatographic results obtained by solid phase microextraction−gas chromatography (SPME−GC), applied to the vapor phase in equilibrium with coffee (HS−SPME), or to coffee extracts (LS−SPME). The capabilities of this method are illustrated by some examples defining the differentiation of coffee samples of different origins or in mixtures of different compositions. Keywords: Roasted coffees; beverages; solid phase microextraction (SPME); GC; principal component analysis (PCA)
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
Measurements have been made of the rate of infusion of caffeine into distilled water from medium roast Kenyan Arabica coffee beans and from eight sieved fractions of the ground beans at 25.8°C. The first-order rate constants increased dramatically as the particle size decreased. For one of the size fractions the rate constants were then measured at various temperatures up to 84.1°C and were found to rise eight-fold over this temperature interval. The partition coefficients of caffeine between ground beans and water were also determined. These results, interpreted by a new steady-state theory of extraction, show that the rate-determining step in the infusion is diffusion of caffeine through the swollen coffee particles. The low magnitude of the diffusion coefficient and its high activation energy demonstrate that caffeine diffusion within the bean particles is a hindered process.
The highly volatile, potent odorants of coffee samples were evaluated by gas chromatography-olfactometry of decreasing headspace samples (GCO-H). 2,3-Butanedione, 2,3-pentanedione, 3-methyl-2-butenthiol (I), methional, 2-furfurylthiol (II) and 3-mercapto-3-methylbutylformate (III) were the key odorants of both, the powders of Arabica and Robusta coffees. 2-Methyl-3-furanthiol (IV), 2,3-diethyl-5-methylpyrazine and an unknown compound were additional key odorants of the latter. An increase in the odour potencies of acetaldehyde, propanal, methylpropanal, 3-methylbutanal and dimethyltrisulphide as well as a decrease in the odour potencies of the thiols I to IV in the brews were the major differences with regard to the powders.
22 acids in ground roast coffees and instant coffees were determined by GLC of their silyl derivatives (after preseparation by gel electrophoresis) or isotachophoresis. The contribution to the total acidity (which was estimated by titration to pH 8 after cation exchange of the coffee solutions) was calculated for each individual acid. The mentioned acids contribute with 67% (roast coffee) and 72% (instant coffee) to the total acidity. In the first place citric acid (12.2% in roast coffee/10.7% in instant coffee), acetic acid (11.2%/8.8%) and the high molecular weight acids (8%/9%) contribute to the total acidity. Also to be mentioned are the shares of chlorogenic acids (9%/4.8%), formic acid (5.3%/4.6%), quinic acid (4.7%/5.9%), malic acid (3.9%/3%) and phosphoric acid (2.5%/5.2%). A notable difference in the contribution to total acidity between roast and instant coffee was found for phosphoric acid and pyrrolidonecarboxylic acid (0.7%/1.9%). It can be concluded that those two acids are formed or released from e.g. their esters in higher amounts than other acids during the production of instant coffee.
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.
Addition of the total melanoidin fraction isolated by water extraction from medium-roasted coffee powder to a model solution containing a set of 25 aroma compounds mimicking the aroma of a coffee brew reduced, in particular, the intensity of the roasty, sulfury aroma quality. Model studies performed by static headspace analysis revealed that especially three well-known coffee odorants, that is, 2-furfurylthiol (FFT), 3-methyl-2-butene-1-thiol, and 3-mercapto-3-methylbutyl formate, were significantly reduced in the headspace above an aqueous model solution when melanoidins were added. In particular, the low molecular weight melanoidins (1500-3000 Da) led to the most significant decrease in FFT. In contrast, for example, aldehydes remained unaffected by melanoidin addition.
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%.
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%.
Grinding is a critical step in the preparation of espresso coffee (EC). The addition of sugar during the torrefacto roasting process could influence the degree of brittleness and grinding. The aim of this work was to study the influence of the grinding grades (coarse, fine, and very fine) in Arabica/Robusta 20:80, natural roasted (A20:R80), and Arabica/Robusta 20:80 with 50% Robusta torrefacto roasted (A20:R80 50% torrefacto) on the chemical and sensorial characteristics of EC in order to select the optimal espresso grinding grade. A higher percentage of coarse particles was found in A20:R80 ground coffee. In both ECs, the extraction of solids and soluble and aroma compounds increased inversely with particle size. Higher foam indices and extraction yields were found in A20:R80 50% torrefacto ECs probably due to the solubilization of caramelized sugar and melanoidins. It has been suggested that the range of an acceptable extraction yield could be extended to 25% in A20:R80 50% torrefacto ECs. In conclusion, the optimal grinding grade for the obtainment of an EC with A20:R80 was fine and that for A20:R80 50% torrefacto was coarse.
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%.
Influence of technological variables on espresso coffee quality. Antioxidant and pro-oxidant capacity of coffee
- Andueza
Andueza S, Influence of technological variables on espresso coffee quality. Antioxidant and pro-oxidant capacity of coffee. Doctoral thesis, University of Navarra. (2003).
Tomo 1. Alimentación
- AENOR
The Science of Quality
- Petracco
Tomo 1. Alimentación. Recopilación de normas UNE
- Análisis Aenor
- Sensorial
- AENOR
Qualitative and quantitative investigations. 14th Int Coloq Chem Coffee
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