Roasting green coffee beans using spouted bed roaster: changes in physical characteristics

Pea-berry grade of green coffee (Coffea arabica)
beans were roasted in a laboratory model spouted bed
roaster at different temperatures (150–250°C) and times
(30–300 s). The roasted samples were analysed for
instrumental colour (hue, chroma and brightness) and
texture. Brightness of the roasted samples varied between
5.2 and 20.4%, and time of roasting markedly decreased the
brightness values. The chroma showed a curvilinear
decrease with both time and temperature of roasting; the
lowest values were with highest roasting times and temperatures.
The hue or dominant wavelength increased from
576 to 603 nm due to roasting. The maximum force offered
by the roasted beans decreased with temperature and/or
time of roasting. An appropriate condition for spouted bed
roasting of green coffee beans was obtained considering
colour of samples and desirable low failure/fracture force.