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Smrke S, Eiermann A, Yeretzian C. The role of fines in espresso extraction dynamics. Sci Rep 2024; 14:5612. [PMID: 38453983 PMCID: PMC10920694 DOI: 10.1038/s41598-024-55831-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Accepted: 02/28/2024] [Indexed: 03/09/2024] Open
Abstract
The impact of particle size distribution of coffee grounds on espresso extraction was explored. Finely ground coffee for espresso has a characteristically bimodal particle size distribution. For a given median grind size, different grinding technologies can yield a different share of fines (particles < 100 µm). We performed espresso extractions for a range of median particle sizes and systematically varying the share of fines by adding sieved fines to the coffee grounds. Dynamic beverage weights, extraction percentage, extraction time and dynamic headspace PTR-MS (proton-transfer mass spectrometer) analysis and sensory evaluation of the resulting brews were measured. We show that the share of fines plays a key role in the espresso extraction flow rate. An increase of share of fines decreases coffee bed permeability, leads to reduced flow rates and longer extraction times. A statistical model using partial least squares regression of the particle size distributions of coffee grounds confirms that fines decrease the coffee bed permeability. The PTR-MS analysis shows a non-linear increase of aroma compounds in the cup with increasing extraction yield. Our hypothesis is that both extraction efficiency and post-extraction evaporative losses of aroma compounds influence the final aroma compound concentrations in the cup.
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Affiliation(s)
- Samo Smrke
- Institute of Chemistry and Biological Chemistry, Coffee Excellence Center, Zurich University of Applied Sciences, Einsiedlerstrasse 31, 8820, Wädenswil, Switzerland.
| | | | - Chahan Yeretzian
- Institute of Chemistry and Biological Chemistry, Coffee Excellence Center, Zurich University of Applied Sciences, Einsiedlerstrasse 31, 8820, Wädenswil, Switzerland
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Mo C, Johnston R, Navarini L, Liverani FS, Ellero M. Exploring the link between coffee matrix microstructure and flow properties using combined X-ray microtomography and smoothed particle hydrodynamics simulations. Sci Rep 2023; 13:16374. [PMID: 37773195 PMCID: PMC10541431 DOI: 10.1038/s41598-023-42380-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2023] [Accepted: 09/09/2023] [Indexed: 10/01/2023] Open
Abstract
Coffee extraction involves many complex physical and transport processes extremely difficult to model. Among the many factors that will affect the final quality of coffee, the microstructure of the coffee matrix is one of the most critical ones. In this article, we use X-ray micro-computed (microCT) technique to capture the microscopic details of coffee matrices at particle-level and perform fluid dynamics simulation based on the smoothed particle hydrodynamics method (SPH) with the 3D reconstructured data. Information like flow permeability and tortuosity of the matrices can be therefore obtained from our simulation. We found that inertial effects can be quite significant at the normal pressure gradient conditions typical for espresso brewing, and can provide an explanation for the inconsistency of permeability measurements seen in the literature. Several types of coffee powder are further examined, revealing their distinct microscopic details and resulting flow features. By comparing the microCT images of pre- and post-extraction coffee matrices, it is found that a decreasing porosity profile (from the bottom-outlet to the top-inlet) always develops after extraction. This counterintuitive phenomenon can be explained using a pressure-dependent erosion model proposed in our prior work. Our results reveal not only some important hydrodynamic mechanisms of coffee extraction, but also show that microCT scan can provide useful microscopic details for coffee extraction modelling. MicroCT scan establishes the basis for a data-driven numerical framework to explore the link between coffee powder microstructure and extraction dynamics, which is the prerequisite to study the time evolution of both volatile and non-volatile organic compounds and then the flavour profile of coffee brews.
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Affiliation(s)
- Chaojie Mo
- Basque Center for Applied Mathematics (BCAM), Alameda de Mazarredo 14, 48009, Bilbao, Spain.
- Aircraft and Propulsion Laboratory, Ningbo Institute of Technology, Beihang University, Ningbo, 315100, People's Republic of China.
| | - Richard Johnston
- Faculty of Science and Engineering, Swansea University, Swansea, SA1 8EN, UK
| | | | | | - Marco Ellero
- Basque Center for Applied Mathematics (BCAM), Alameda de Mazarredo 14, 48009, Bilbao, Spain
- Zienkiewicz Centre for Computational Engineering (ZCCE), Swansea University, Bay Campus, Swansea, SA1 8EN, UK
- IKERBASQUE, Basque Foundation for Science, Calle de María Díaz de Haro 3, 48013, Bilbao, Spain
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An equilibrium desorption model for the strength and extraction yield of full immersion brewed coffee. Sci Rep 2021; 11:6904. [PMID: 33767250 PMCID: PMC7994670 DOI: 10.1038/s41598-021-85787-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2020] [Accepted: 02/28/2021] [Indexed: 11/29/2022] Open
Abstract
The sensory qualities of brewed coffee are known to be strongly correlated with the total dissolved solids (TDS) and extraction yield (E) of the brew. Here, we derive a predictive model for the TDS and E of full immersion brewed coffee using a pseudo-equilibrium desorption approach. Assuming a single, species-averaged equilibrium constant \documentclass[12pt]{minimal}
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\begin{document}$$K$$\end{document}K yields theoretical predictions indicating that the TDS is approximately inversely proportional to the water/coffee mass brew ratio, while E is independent of the brew ratio. Our experimental results strongly accord with both theoretical predictions, and indicate that E is approximately 21% over a wide range of brew ratios. An analysis of the standard oven-drying method for measuring E indicates that it yields significant underestimates of the true value at equilibrium, due to retained brew within the spent moist grounds. We further demonstrate that \documentclass[12pt]{minimal}
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\begin{document}$$K$$\end{document}K is insensitive to grind size, roast level, and brew temperature over the range 80–99 °C. Taken together, our results indicate that full immersion brewing offers precise control over the TDS at equilibrium but little control over E, and that practitioners should pay careful attention to their brew ratio as the most important parameter for full-immersion brewing.
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Eiermann A, Smrke S, Guélat LM, Wellinger M, Rahn A, Yeretzian C. Extraction of single serve coffee capsules: linking properties of ground coffee to extraction dynamics and cup quality. Sci Rep 2020; 10:17079. [PMID: 33051489 PMCID: PMC7553981 DOI: 10.1038/s41598-020-74138-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2020] [Accepted: 09/24/2020] [Indexed: 11/10/2022] Open
Abstract
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.
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Affiliation(s)
- André Eiermann
- UCC Coffee Switzerland AG, Bernstrasse 180, 3052, Zollikofen, Switzerland
| | - Samo Smrke
- Institute of Chemistry and Biological Chemistry, Coffee Excellence Center, Zurich University of Applied Sciences, Einsiedlerstrasse 31, 8820, Wädenswil, Switzerland
| | - Loïc-Marco Guélat
- UCC Coffee Switzerland AG, Bernstrasse 180, 3052, Zollikofen, Switzerland
| | - Marco Wellinger
- Institute of Chemistry and Biological Chemistry, Coffee Excellence Center, Zurich University of Applied Sciences, Einsiedlerstrasse 31, 8820, Wädenswil, Switzerland
| | - Anja Rahn
- Institute of Chemistry and Biological Chemistry, Coffee Excellence Center, Zurich University of Applied Sciences, Einsiedlerstrasse 31, 8820, Wädenswil, Switzerland
| | - Chahan Yeretzian
- Institute of Chemistry and Biological Chemistry, Coffee Excellence Center, Zurich University of Applied Sciences, Einsiedlerstrasse 31, 8820, Wädenswil, Switzerland.
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Beverly D, Lopez-Quiroga E, Farr R, Melrose J, Henson S, Bakalis S, Fryer PJ. Modeling Mass and Heat Transfer in Multiphase Coffee Aroma Extraction. Ind Eng Chem Res 2020; 59:11099-11112. [PMID: 32565616 PMCID: PMC7304076 DOI: 10.1021/acs.iecr.0c01153] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 05/25/2020] [Accepted: 05/27/2020] [Indexed: 11/28/2022]
Abstract
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Instant coffee manufacture involves
the aqueous extraction of soluble
coffee components followed by drying to form a soluble powder. Loss
of volatile aroma compounds during concentration through evaporation
can lower product quality. One method of retaining aroma is to steam-strip
volatiles from the coffee and add them back to a concentrated coffee
solution before the final drying stage. A better understanding of
the impact of process conditions on the aroma content of the stripped
solution will improve product design stages. In this context, we present
a multiscale model for aroma extraction describing (i) the release
from the matrix, (ii) intraparticle diffusion, (iii) transfer into
water and steam, and (iv) advection through the column mechanisms.
Results revealed (i) the existence of three different types of compound
behavior, (ii) how aroma physiochemistry determines the limiting kinetics
of extraction, and (iii) that extraction for some aromas can be inhibited
by the interaction with other coffee components.
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Affiliation(s)
- David Beverly
- Jacobs Douwe Egberts R&D, Banbury OX16 2QU, U.K.,School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K
| | - Estefanía Lopez-Quiroga
- School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K
| | - Robert Farr
- Jacobs Douwe Egberts R&D, Banbury OX16 2QU, U.K
| | | | - Sian Henson
- Jacobs Douwe Egberts R&D, Banbury OX16 2QU, U.K
| | - Serafim Bakalis
- Faculty of Engineering, University Park, Nottingham NG7 2RD, U.K
| | - Peter J Fryer
- School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K
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Moroney KM, O’Connell K, Meikle-Janney P, O’Brien SBG, Walker GM, Lee WT. Analysing extraction uniformity from porous coffee beds using mathematical modelling and computational fluid dynamics approaches. PLoS One 2019; 14:e0219906. [PMID: 31365538 PMCID: PMC6668809 DOI: 10.1371/journal.pone.0219906] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Accepted: 07/04/2019] [Indexed: 11/18/2022] Open
Abstract
Achieving a uniform extraction of soluble material from a porous matrix is a generic problem in various separation and filtration operations, with applications in the food processing, chemical and pharmaceutical industries. This paper describes models of fluid flow and transport of soluble material within a packed granular bed in the context of coffee extraction. Coffee extraction is described by diffusion of soluble material from particles of one or more representative sizes into fluid flowing through the packed bed. One-dimensional flow models are compared to computational fluid dynamics (CFD) models. A fine and a coarse coffee grind are considered. Model results are compared to experimental data for a packed cylindrical coffee bed and the influence of a change in geometry to a truncated cone is considered. Non-uniform flow in the truncated cone causes significant variation in the local extraction level. Coffee extraction levels during brewing are analysed using extraction maps and the degree of variation is represented on the industry standard coffee brewing control chart. A high variation in extraction yield can be expected to impart bitter flavours into the brew and thus is an important variable to quantify.
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Affiliation(s)
- Kevin M. Moroney
- Synthesis and Solid State Pharmaceutical Centre (SSPC), Bernal Institute, University of Limerick, Limerick, Ireland
- MACSI, Department of Mathematics and Statistics, University of Limerick, Limerick, Ireland
- * E-mail:
| | - Ken O’Connell
- Department of Chemical Sciences, University of Limerick, Limerick, Ireland
| | - Paul Meikle-Janney
- Dark Woods Coffee, Holme Mills, West Slaithwaite Road, Marsden, Huddersfield, United Kingdom
| | - Stephen B. G. O’Brien
- MACSI, Department of Mathematics and Statistics, University of Limerick, Limerick, Ireland
| | - Gavin M. Walker
- Department of Chemical Sciences, University of Limerick, Limerick, Ireland
| | - William T. Lee
- MACSI, Department of Mathematics and Statistics, University of Limerick, Limerick, Ireland
- University of Huddersfield, Huddersfield, United Kingdom
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Lopes GR, Passos CP, Rodrigues C, Teixeira JA, Coimbra MA. Modulation of infusion processes to obtain coffee-derived food ingredients with distinct composition. Eur Food Res Technol 2019. [DOI: 10.1007/s00217-019-03318-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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