Experimental study of dynamic porosity and its effects on simulation of the coffee beans roasting

Abstract We investigated coffee beans porosity to demonstrate its effects on predicting heat and mass transfer during roasting. Calculated porosity from experimental data from electronic microscopy pore size and distribution for green bean and roasted beans were evaluated. Porosity of 9.8% and 34.2% for green and roasted beans were found. These values defined the limits of a dynamic model, which was developed and introduced as subroutine into a 3-D modeling of coffee roasting. Hot air at 473 K and 503 K roasted single and group beans during 200 s for fixed Reynolds number. Modeled and experimental data of temperature from Arabica bean agreed well. It was observed that porosity affected heat and moisture loss rate during roasting. The results can help to understanding the roasting process, or studying processes of food products that require roasting by means of hot air, like grains or seeds.