School of Chemical Engineering, University of Birmingham, B15 2TT, UK; Jacobs Douwe Egberts, R&D Offices, OX16 2QU, UK.
School of Chemical Engineering, University of Birmingham, B15 2TT, UK.
Food Res Int. 2023 Jan;163:112253. doi: 10.1016/j.foodres.2022.112253. Epub 2022 Nov 29.
Physicochemical transformation of coffee during roasting depends on the applied time-temperature profile (i.e., rate of heat transfer), with heat transfer phenomena governed by particle dynamics. Positron Emission Particle Tracking (PEPT), a non-invasive imaging technique, was used here to characterise the granular flow of coffee in a real, pilot-scale rotating drum roaster. The experimental study established the impact of drum speed, batch size and bean density (i.e., roast degree) on the system's particle dynamics. Particle motion data revealed two distinct regions: (i) a disperse (low occupancy, high velocity) region of in-flight particles and (ii) a dense (high occupancy, low velocity) bean bed. Implications of these results for heat transfer suggest that controlling drum speed for different density coffees will provide roaster operators with a tool to modulate conductive heat transfer from the heated drum to the bean bed. These comprehensive data thus inform roasting best practices and support the development of physics-driven models coupling heat and mass transfer to particle dynamics.
咖啡在烘焙过程中的物理化学变化取决于所采用的时间-温度曲线（即传热速率），而传热现象受颗粒动力学控制。正电子发射颗粒跟踪（PEPT）是一种非侵入性的成像技术，本文将其用于描述实际的、中试规模的旋转滚筒烘焙机中咖啡的颗粒流动。该实验研究确定了滚筒速度、批次大小和豆密度（即烘焙程度）对系统颗粒动力学的影响。颗粒运动数据揭示了两个不同的区域：（i）飞行颗粒的离散（低占有率、高速度）区域和（ii）密集（高占有率、低速度）豆床。这些结果对传热的影响表明，控制不同密度咖啡的滚筒速度将为烘焙操作人员提供一种工具，以调节从加热滚筒到豆床的传导传热。这些全面的数据为烘焙最佳实践提供了信息，并支持开发将热量和质量传递与颗粒动力学相结合的物理驱动模型。
