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Item type:Publication, Access status: without files , Tuning the packed bed configuration for selective extraction of espresso non-volatiles based on polarityThe taste of espresso is impacted by the absolute and relative concentrations of numerous marker compounds extracted during the brewing process. Due to the complex diffusion-convection process, the resulting concentration of the compounds in the espresso cup is largely influenced by the extraction conditions. In our previous work (Vaca Guerra et al., 2023) we have demonstrated that the hydrodynamics of extraction is significantly impacted by the size distribution of the coffee particles. In the present work, using a similar approach, we evaluated its impact on the kinetics of the extraction of specific coffee marker compounds. The results obtained show that, even having similar extraction conditions, changes in the bed configuration, namely reducing the specific wetting surface area, decreased the extraction rate of the components asymptotically. Moreover, being polar components the most affected and non-polar the least, the impact of particle size was correlated with the polarity of the components, showing good agreement. This work provides insight into the possible ways to perform selective extraction from components with different polarities driven only by variations of the initial bed parameters and evaluating the necessary conditions to scale up the results to larger bed lengths.Publicationtype: Journal Article67 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Influence of particle size distribution on espresso extraction via packed bed compressionEspresso 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.Publicationtype: Journal Article92