Analysing extraction uniformity from porous coffee beds using mathematical modelling and computational fluid dynamics approaches

Kevin M. Moroney, Ken O'Connell, Paul Meikle-Janney, Stephen B.G. O’Brien, Gavin M. Walker, William Lee

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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.
Original languageEnglish
Article numbere0219906
Number of pages24
JournalPLoS One
Volume14
Issue number7
Early online date31 Jul 2019
DOIs
Publication statusPublished - 31 Jul 2019

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