Evaluation of Physical Properties of Coffee During Roasting

The main objective of the present study was to evaluate the variation of physical properties of coffee beans during roasting. Characteristics evaluated were: volume, bean and bulk densities, weight loss, and color. Experiments were conducted using a lab-scale roaster, with coffee samples being collected at regular intervals during roasting. The results showed that both volume and weight loss increase during roasting, and that such increase can be described by two lines presenting different slopes, coinciding with the drying and pyrolysis stages. It was also observed that both bulk and bean densities decrease during roasting, due to the increase in volume and simultaneous decrease in mass. The results also show that the variations in color parameters are more expressive at the onset of pyrolysis.