New article in the industrial collaboration between Illy Caffe’ and the CFD Modelling and Simulation group

The goal of this project is to develop a modelling-simulation framework to understand and 'virtually' monitor the balance of taste-actives compounds in the beverage under unexplored flow processing conditions

BCAM's CFD Modelling and Simulation research group led by Prof. Marco Ellero together with Dr. Luciano Navarini, head of Scientific and Research Division at Illy, has published in the journal Physics of Fluids a new article focusing on the modelling of flow-induced mechanical erosion during coffee extraction.

This article focuses on the espresso extraction process involving complex transport within a porous medium of changing geometry. The large solid grains that form the bulk of the porous medium can migrate, swell and consolidate, and can also change morphologically during flow, i.e. be mechanically eroded by hydrodynamic forces. These processes can, in turn, have an important secondary effect on the flow and related coffee extraction profiles. In this paper, they design a model of upward erosion in the framework of smoothed dissipative particle dynamics to account for flow-induced morphological changes of coffee beans.

Coffee beans are not completely wetted and remain fragile. Heterogeneity can be induced both in the seepage direction and in the transverse direction. 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 limited to the modelling of espresso extraction, our model can also be applied to other eroded porous media. The results of this paper suggest that, under ideal porous flow conditions, the heterogeneity (both in the direction of pressure drop and in the transverse direction) of an eroding medium can be controlled by tuning the performance characteristics of the eroding material.

The project it is based in the percolation of hot water through ground coffee represents a complex thermo-fluid dynamics process where particulates and aromatics migrate from the grains into the brew. Distinct compounds kinetics generally lead to an altered balance in the final cup depending on extraction times, ground coffee granulometry, applied pressures and temperatures, and finally, to a very different sensorial experience.

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