Critical examination of particle swelling during wetting of ground coffee

Maille, Matthew J.; Sala, Kyle; Scott, D. M.; Zukswert, Hannah

doi:10.1016/j.jfoodeng.2020.110420

Cited by 8 publications

(8 citation statements)

References 7 publications

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“…a porous medium is only one of the many important physical processes occurring inside a coffee cake during extraction. Other highly-relevant effects are related to consolidation and compaction 59,60 , fragment migrations 4,16 and grain swelling 61,62 , to mention but a few. To further improve the mesoscopic modeling of espresso extraction in the future we plan to model the coffee grains as quasi-rigid body to consider both the consolidation and fracture of the grains.…”

Section: Discussionmentioning

confidence: 99%

Modeling the effect of flow-induced mechanical erosion during coffee filtration

Johnston

Navarini³

et al. 2021

Physics of Fluids

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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.

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Section: Discussionmentioning

confidence: 99%

Modeling the effect of flow-induced mechanical erosion during coffee filtration

Johnston

Navarini³

et al. 2021

Physics of Fluids

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“…In addition, there is still no consensus on whether roast coffee particles swell during extraction and how much is the degree of swelling, if it does occur. The conclusion drawn by previous researchers varies from no swelling whatsoever 13,14 to about 7% 15 or 15% increase in size 6,16 . The reason for these mixed opinions is that, the initial particle size, the degree of roast, and the water chemistry could all affect the process, making the problem difficult to solve.…”

Section: Introductionmentioning

confidence: 83%

“…However, it is unlikely that coffee particles can really swell to such a degree. Experimental measurements on the swelling degree of coffee particles range from no swelling at all to 15% of swelling in size 6,[13][14][15][16] . In this article we consider only a moderate degree of swelling (<8%).…”

Section: Swelling Modelmentioning

confidence: 99%

“…The reason for these mixed opinions is that, the initial particle size, the degree of roast, and the water chemistry could all affect the process, making the problem difficult to solve. Finally, different measurement protocols using different inspection methods (microscopy and laser diffraction) could also introduce errors in the estimate of swelling degree 14 .…”

Section: Introductionmentioning

confidence: 99%

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Modeling swelling effects during coffee extraction with smoothed particle hydrodynamics

Navarini²,

Liverani³

et al. 2022

Physics of Fluids

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It is commonly assumed that coffee particles swell during filtration, but it has not been clarified how different degrees of swelling affect the extraction. In this article, we propose a grain swelling model to investigate the influences of swelling on both intra-grain and inter-grain transport. The swelling is modeled through a diffusion process of excess water into the grains. The geometric expansion of the grains is connected to the local concentration of excess water through a specified deformation gradient tensor. Diffusion of soluble compounds inside the grains is coupled with the swelling dynamics through a modified diffusion equation. Inter-grain transport is modeled by solving the Navier–Stokes equation and diffusion equations. This model is solved numerically in the framework of smoothed particle hydrodynamics, and it is used to simulate the extraction of a minimal coffee bed setup and to investigate the effect of a small degree of particle swelling ([Formula: see text] in size) on the extraction kinetics. It is found that under the normal operating parameter regime of espresso filtration, swelling affects the extraction mainly through the change of inter-grain transport. Swelling also alters the diffusion inside the grains, but this process has a secondary effect on the extraction. In general, swelling slightly impedes the extraction rate, but enhances the strength considerably at both fixed brewing time and fixed brewing volume. Our results justify the endeavor in the literatures to clarify the effect of possible swelling on brewing and preparation variables during coffee extraction.

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“…Se evaluaron las propiedades Organolépticas Las partículas de café sumergidas en agua no se hinchan apreciablemente la escala de tiempo de interés (0,5 -5 minutos) [41] típica…”

Section: Efecto En Las Propiedadesunclassified

Effect of Grinding and Sieving on the Coffee Properties: A Systematic Review

Justiniano¹,

Velásquez²,

Zenteno³

et al. 2022

Proceedings of the 20th LACCEI International Multi-Conference for Engineering, Education and Technology: “Education, Research A

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The coffee bean is widely used in industries in order to transform it into a product apt for human consumption. The processing of coffee requires unitary operations such as harvesting, conditioning, roasting, grinding, sifting, and packaging, which determine the final quality of the coffee. While roasting is known to confer sensory characteristics, grinding and sieving will influence how the flavor and color compounds are extracted. However, to da te there are no systematic reviews in this regard. The objective of this review is to describe and analyze information regarding the application of grinding and sieving in coffee, and to explain their effects on the properties of coffee. The systematic review was conducted under the PRISMA model, the search was conducted in recognized databases, and in a range of 7 years (2015-2021). Thirtyone articles were finally selected to perform the systematic review. As results it was found that grinding is performed to reduce the coffee beans by dividing and/or fractioning, which implies only a physical transformation that should preserve the characteristics of the initial raw material; while sieving retains the larger particles above a certain size, leaving the small particles to pass according to the requirements for the types of coffee. The granulometry of roasted and ground aged coffee is around 610 ± 13.2 μm and for roasted a ndground untreated coffee is 590 ± 14.8 μm. Among the general properties of coffee that will be altered by grinding and sieving are aroma and flavor. If the conditions are adequate, a coffee with an ideal aroma and flavor will be obtained; on the contrary, if the grinding is coarse the coffee will be watery, without aroma or cream, and if it has a floury consistency, it will have less aroma and m o re bitterness. However, it is important to mention that the properties of coffee also depend on the origin, variety picked, drying and roasting of the coffee. Therefore, it can be concluded that there should be adequate conditions of grinding and sieving so that the coffee particles during its use present positive effects, providing and intensifying its aroma and flavor of the final beverage.

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Critical examination of particle swelling during wetting of ground coffee

Cited by 8 publications

References 7 publications

Modeling the effect of flow-induced mechanical erosion during coffee filtration

Modeling the effect of flow-induced mechanical erosion during coffee filtration

Modeling swelling effects during coffee extraction with smoothed particle hydrodynamics

Effect of Grinding and Sieving on the Coffee Properties: A Systematic Review

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