Coffee bean particle motion in a spouted bed measured using Positron Emission Particle Tracking (PEPT)

• Published in: Journal of food engineering Vol. 311; p. 110709
• Main Authors: Al-Shemmeri, Mark, Windows-Yule, Kit, Lopez-Quiroga, Estefania, Fryer, Peter J.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2021
• Subjects: Air-to-bean ratio; beans; coffee beans; Coffee roasting degree and density; electrons; heat; heat treatment; mass transfer; Particle motion modelling; Positron emission particle tracking (PEPT); Spouted bed of coffee beans; Spouted bed of coffee beans; Particle motion modelling; Positron emission particle tracking (PEPT); Air-to-bean ratio; Coffee roasting degree and density
• ISSN: 0260-8774; 1873-5770
• DOI: 10.1016/j.jfoodeng.2021.110709

Coffee roasting is a heat treatment process that transforms green coffee into a product that can subsequently be ground and brewed. Understanding roasting is critical in developing new downstream processes and formulations, as well as in optimising existing ones. Positron Emission Particle Tracking (PEPT) allows tracking of particles in process equipment and has been used here to characterise particle dynamics of coffee beans within a spouted bed roaster subject to varying air-to-bean ratios without roasting. Occupancy profiles associated with each air-to-bean ratio have been determined and two distinct regions identified: (i) a dense bean bed of high occupancy (ii) a dilute freeboard of lower occupancy. Results also revealed the effect of coffee density on particle dynamics within the roaster. Overall, this work demonstrates that PEPT can be a useful tool to generate data regarding granular flow patterns in roasters that might be used to improve existing heat and mass transfer models for roasting. •Positron Emission Particle Tracking (PEPT) maps the flow of coffee beans in a spouted bed.•The impact of air-to-bean ratio and bean density on particle dynamics is established.•Flow in the dilute freeboard and dense bean bed have been identified.•Individual particle trajectories reveal residence times in each region.•The potential to couple particle motion with heat and mass transfer is highlighted.