Mathematical modeling of drying kinetics and volumetric shrinkage of coffee beans

In order to contribute to improving the quality of coffee and optimizing its drying process, the aim of the study was to fit mathematical models to describe the drying kinetics and volumetric shrinkage of coffee beans during the drying stage. Additionally, the influence of drying on the physical properties of coffee beans was evaluated. Immature, processed, and peeled coffee beans were used and subjected to drying temperatures of 30, 35, and 40 °C. The dryer used was a prototype with temperature control and constant airflow, with a drying airflow velocity of 1.0 m s-1. The modified Henderson and Pabis model provided the best fit to the experimental drying data. As for the volumetric shrinkage of coffee beans, the modified Bala & Woods, Polynomial, and Lang and Sokhansanj models showed good fits to the experimental data. Furthermore, the apparent bulk density of immature coffee beans varied during the drying process, with a reduction at the end of the drying process at all studied temperatures. The results indicate that it was possible to adjust the drying kinetics and volumetric shrinkage data to mathematical models, which can contribute to the prediction of coffee drying processes.