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Accurate and repeatable extraction of solubles from roasted and ground coffee with hot water is vital to produce consistently high quality coffee in a variety of brewing techniques. Despite this, there is an absence in the literature of an experimentally validated model of the physics of coffee extraction. In this work, coffee extraction from a cof...
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... the experiments presented here we make use of five different coffee grinds ranging from a fine drip filter grind to a very coarse grind. The grind size distributions of these grinds are shown in figure 9. The first grind is a relatively fine grind, called Jacobs Krönung (JK) standard drip filter coffee grind. ...
Context 2
... second extremely coarse grind was obtained using the # 30 setting on the grinder. The grind size distribution of the Cimbali # 30 grind was too coarse to be analysed by the optical particle size analyzer used (Mastersizer 2000; Malvern Instruments Ltd, UK) and so is not included in figure 9. ...
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The drip filter coffee market is a multi-billion euro industry. Despite this, although the chemistry of coffee brewing has been investigated in great detail, the physics of the process has received relatively little attention. In order to explain in scientific terms correlations between the coffee quality and the process variables, a physical model...
Citations
... The same solving strategy is also adopted in [15] where the percolation model is generalised for the prediction of an arbitrary number of chemical compounds. All these one-dimensional percolation models have the advantage to be simple computational tools to predict the global water flow and extraction dynamics, considering quantities averaged over the whole domain or over some domain sections [16]. The only three-dimensional model, considering the main percolation processes and endowed with numerical simulations and a preliminary experimental validation, can be found in [17]. ...
Coffee is one of the most consumed beverages in the world. This has two main consequences: a high level of competitiveness among the players operating in the sector and an increasing pressure from the supply chain on the environment. These two aspects have to be supported by scientific research to foster innovation and reduce the negative impact of the coffee market on the environment. In this paper, we describe a mathematical model for espresso coffee extraction that is able to predict the chemical characterisation of the coffee in the cup. Such a model has been tested through a wide campaign of chemical laboratory analyses on espresso coffee samples extracted under different conditions. The results of such laboratory analyses are compared with the simulation results obtained using the aforementioned model. The comparison shows a close agreement between the real and in silico extractions, revealing that the model is a very promising scientific tool to take on the challenges of the coffee market.
... During this process, known as percolation, the water dissolves various chemical substances contained in the powder in two main phases: (i) the imbibition, where the hot water driven by gravity flows through the grains and seeps into the single grain by capillarity, (ii) the extraction, where pressurised hot water transports the dissolved substances from the grains to the coffee cup. In particular, most of such substances comes from the small grains, whereas the substances in big grains are only partially dissolved (Moroney et al. 2015). The extraction by pressurised hot water is obtained by the high pressure imposed at the top surface of the coffee pod that allows the water to go against the resistance of the compact porous medium. ...
... In the numerical simulations, the physico-chemical parameters used in the model have been taken in the literature: the solid diffusivity D s = 6.25 · 10 −10 m 2 /s (Cameron et al. 2020), the liquid diffusivity D = 1.0 · 10 −8 m 2 /s (Cameron et al. 2020), the concentration of saturation c sat = 212.4 kg/m 3 (Cameron et al. 2020), the initial solid concentration c s0 = 200 kg/m 3 (Moroney et al. 2015) considering the extractable mass of coffee grains at 90 • C reaching about 30% of the coffee bed, the total solid fraction φ s = 0.8272 (Cameron et al. 2020), whereas the reaction rate k r = 6.0 · 10 −9 m 7 /kg 2 has been fitted to the experiments. Regarding the parameters of the discretisation scheme, we choose N = 4, M = 5 thus the orders of the length of space steps are h z ≈ 10 −3 , h f ≈ 10 −6 , h b ≈ 10 −5 ; time steps are N t = 1000 thus h t ≈ 10 −2 ; the parameter m in (13) is 0.1. ...
Advection–diffusion–reaction equations are largely exploited in applied science, for their ability to describe real-life phenomena where mass transport and diffusion, as well as chemical reactions, occur. Here, these models are used to describe the percolation phenomena arising in espresso coffee extraction. The resulting initial/boundary value problem is solved using the Crank–Nicolson scheme and a nested fixed-point iteration. Mass conservation and positivity of the solution are guaranteed. The reliability of the model together with the proposed solving strategy is assessed experimentally, by comparing the efficiency of real and simulated extractions conducted under different physico-chemical conditions.
... The understanding and description of the espresso coffee extraction have been the focus of interest during the recent years in the scientific community. The published works have been dedicated to describing the extraction process, especially regarding the optimization of the brew quality [7], [8], which has been proven to be related to the extracted compound composition in the final cup [9]. Several studies have confirmed that the water temperature and particle size distribution, among all the other variables, predominantly impact the extracted components compositions. ...
... We consider that the coffee-packed bed undergoes a series of physical changes during extraction process, due to soluble material being extracted, particle swelling etc. [1], [5]. The particle and bed porosity changes have been considered relevant for espresso extraction modeling [7]. For this reason, we focus in this work on studying the impact of the dry bed porosity on permeability, as the initial condition that states the microscopic scale phenomena; correlated to the effects at a macroscopic scale. ...
Espresso extraction is a diffusion-convection process involving both intra-granular pores, and the intergranular pores of the packed bed. Bed hydrodynamics and overall end-cup quality are governed by the bulk porosity, set by the dry coffee bed compression before extraction. In this work, the impact of the initial bed compression on the water permeability during espresso extraction is studied. Coarse fractions of the bimodal coffee particle size distributions were characterized by the particle mean size α and the size uniformity β of the distribution. It was found that under the same axial compression lower bed porosities were obtained with decreasing size uniformity β, even at larger mean size α. A model was developed to predict the dry packed bed porosity. Extraction experiments confirmed that low permeability desired during espresso brewing was found not to be exclusive to distributions with low mean particle sizes. Rather, it can also be achieved by tuning compression force, α, and β together. A modified Kozeny-Carman expression was derived to explain and predict the observed permeability results.
... In brewing an espresso hot (92-95 • C) water is forced at high pressure (9-10 atmospheres) through a bed of 15-22 g of finely ground coffee resulting in a beverage with a mass of 30-60 g [1]. Although coffee is a a complex mix of nearly 2000 chemicals [6] most mathematical models of coffee brewing treat coffee as a single substance using mass as a measure of the amount. The quality of coffee can be measured by two properties: strength and extraction yield. ...
... investigating the existence and uniqueness of solutions rather than parameterising the model with experimental data. Moroney et al. [6][7][8][9] developed a multiscale model of cafetiere and filter coffee brewing based on models of groundwater flow and leaching. These models describe coffee as a dual porosity medium with pores between grains of ground coffee and pores within ground coffee. ...
... It is estimated as Q = M shot /ρ w t shot . (We follow Ref. [6] in assuming that the fluid volume is unaffected by dissolved coffee content.) To find the flow rates through the individual pathways we use the Kozeny-Carman equation for the permeability of a porous medium of spherical particles [4] to relate porosity to permeability and thus flow resistance. ...
A recent experiment showed that, contrary to theoretical predictions, beyond a cutoff point grinding coffee more finely results in lower extraction. One potential explanation for this is that fine grinding promotes nonuniform extraction in the coffee bed. We investigate the possibility that this could occur due to an instability involving dissolution and flow. A low dimensional model in which there are two possible pathways for flow is formulated and analysed. This model reproduces the qualitative trend observed due to combination of a flow instability and saturation of extraction in one pathway. This strongly suggests that a flow instability can explain the observed decrease in extraction.
... A possible way forward is to make reciprocity amid the thermodynamics and kinetics of the numerous physical, chemical, physicochemical, and biochemical exchanges and the microscale-based knowledge of their respective stoichiometry (Moroney et al., 2015). ...
The complexity of modeling water quality variations in water distribution systems (WDS), studied for decades, stems from multiple constraints and variables involved and the complexity of the system behavior. The conventional macroscale-based WDS water quality models are founded on continuum mechanics. In attempts to provide a broad picture of the multi-species interactions, these models overlook the stochasticity corresponding to the reaction mechanisms within the WDS domain. Furthermore, owing to the black-box type modeling adopted in simulating the multi-species interactions, the existing state-of-the-art models have limitations in representing intermediates and/or by-products formation. Accordingly, they remain ineffective in describing the water chemistry-stoichiometric interactions within the WDS domain. Only a radically new modeling approach could overcome the limitations of the macroscale-based approaches and enables analyzing the stochastic WDS mechanisms by keeping the true nature of the system behavior. Stimulated by the metabolic network modeling principles in systems biology, this article outlines the prospect of developing an innovative 'water'bolic network modeling approach to provide a new outlook to the existing WDS water quality modeling research.
... The particle size of the ground coffee is critically important since it affects the flow rate. The flow rate, in turn, affects both the extent of the contact between the water and the coffee, and its duration, changing the whole extraction kinetic [14]. The short extraction time means that ground beans should contain a minimum percentage of fine particles, to achieve sufficient pressure in the coffee cake, and produce a full body and delicate crema [15,16]. ...
Coffee powder is obtained with a grinding machine. Espresso coffee is prepared when hot water is forced under pressure through the puck of coffee powder, and the optimal espresso flow rate is 1 g s ⁻¹ . However, this flow rate can change for different extractions, forcing baristas to frequently change the setup of the grinder. Grinding grade is one of the most important sources of variation in the quality of espresso. This study tests an innovative method to prepare coffee powder puck, designed to reduce variability in flow rate between extractions. The method is based on stratified layers of ground coffee with different granulometry, and it was tested in three trials with different coffees and grinders. The flow rate associated with the new method (Patent WO/2020/148258- PCT/EP2020/050773) was more stable than the rate in a conventional system, reliability was optimized by placing larger coffee particles at the bottom, and finer particles at the top of the filter basket.
... The higher the roasting temperature, the lower caffeine and phenolic compounds such as chlorogenic acid (Fuller & Rao, 2017;Somporn et al., 2011;Vignoli et al., 2014). Apart from roasting, brewing methods such as decoction, infusion, and pressure methods are also essential factors that affect coffee's sensory 1Department of Food Technology and Nutrition, Faculty of Halal Food Science, Djuanda University, Bogor Indonesia 2 Food Security Offices, Bogor Regional Government, Indonesia quality (Lopez-Galilea et al., 2007;Moroney et al., 2015;Ludwig et al., 2012). Alan (2015) reported that the drip brew method resulted in higher intensity for coffee flavour. ...
Keywords black pepper coffee; consumer profiling; brewing; rapid analysis Black pepper coffee is one of the innovations in Bangka Belitung Province, Indonesia, with a warm characteristic due to the naturally occurring piperine compounds. This study aimed to assess black pepper coffee's sensory profile using the CATA (check-all-that-apply) rapid analysis method and to find the formula and brewing technique liked most by consumers. The study consisted of two stages: determining the sensory attributes of black pepper coffee and obtaining sensory data from coffee-consumers with different coffee and black pepper powder ratios (98:2; 96:4; and 94:6) and brewing methods (cold brew, drip V60 brew, and tubruk). The analysis used in this CATA included the Cochran's Q test, correspondence analysis, principal coordinate analysis (PCoA), and penalty analysis using the XLSTAT 2019 software. The results showed a total of 14 sensory attributes, including bitterness, acidity, sweetness, spiciness, caramel, black tea, dark chocolate, smokiness, hints of black pepper, hints of cinnamon, hints of ginger, hints of lemongrass, brown sugar, and body/ mouthfeel. Statistical analysis showed that the addition of black pepper and type of brewing had a significant effect (5% level) on the sensory attributes of black pepper coffee, except for bitterness, spiciness, and hints of black pepper based on the Cochran's test. According to the panellists, the ideal black pepper coffee had acidity, sweetness, body/mouthfeel, spiciness, hints of black pepper, and bitterness, and the attributes of acidity, sweetness, and hints of black pepper were included as must-have attributes. Based on the overall analysis, cold brew coffee with 4% black pepper was close to the ideal black pepper coffee.
... For a detailed description of the complex physical processes occurring during coffee extraction the reader is referred to the complete review by Melrose et al 8,9 . Physics of coffee extraction has been modelled in some earlier studies 10,11 and some very recent works [12][13][14][15] . Most of these studies rely on continuum models for the concentrations fields suitable coupled to hydrodynamic effects. ...
The espresso extraction process involves a complex transport inside a geometry-changing porous medium. Large solid grains forming the majority of the porous medium can migrate, swell, consolidate and they can also morphologically change during flow, i.e. being mechanically eroded by hydrodynamic forces. These processes can, in turn, have a
significant back-effect on the flow and the related coffee extraction profiles. In this article, we devise a bottom-up erosion model in the framework of smoothed dissipative particle dynamics to consider flow-induced morphological changes of the coffee grains. We assume that the coffee grains are not completely wetted and remain brittle. We found
that heterogeneity in both the filtration direction and the transverse direction can be induced. The former is controlled by the angle of internal friction while the latter is controlled by both the cohesion parameter and the angle of internal friction. Not restricted to the modeling of espresso extraction, our model can also be applied to other eroding porous media. Our results suggest that, under ideal porous flow conditions, we can control the heterogeneity (in both the pressure drop direction and the transverse direction) of an eroding medium by tuning the yield characteristics of the eroding material.
... . Despite the different approaches, the central operation of these methods is the extraction of soluble compounds from the coffee grounds with water, the kinetic of which is affected by variables, in particular grind size, water quality and temperature, brewing time, and brewing ratio (Corrochano, Melrose, Bentley, Fryer, & Bakalis, 2014;Moroney, Lee, O'Brien, Suijver, & Marra, 2015Wang, William, Fu, & Lim, 2016). ...
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
... For these reasons, it is not easy to determine the particle size changes during the grinding process in order to determine its influence on sensory profile in the EC. However, some studies take into consideration the pores between the particles (intergranular) and into the particles (intragranular) in order to assess their influence on the extraction process [96,[101][102][103]. Table 3 summarizes the influence of main parameters on EC extraction and flavor. ...
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.
