PERTANIKA JOURNAL OF TROPICAL AGRICULTURAL SCIENCE

Roasting is the most important step in the coffee processing. The impact of superheated steam roasting temperature (150, 200, 250°C) and time (10-50 min) on the color (L*, a*, b*, browning index), moisture and hardness attributes of Coffea canephora (Robusta coffee) beans were studied. Increases in roasting temperature and time caused a decrease in all the responses except for browning index, a* and b* values of roasted coffee beans. A decrease in the hardness of coffee bean during roasting has been correlated to the loss of moisture content. Coffee beans exhibit greater bean volume, pore volume and larger micropores during roasting process, which indirectly lead to the loss of moisture content. With regards to the prolonged superheated steam roasting, it significantly affects colour attributes and moisture content. As the roasting temperature increased up to 250ºC, colour attributes such as browning index, a* and b* values decreased significantly whereas moisture content increased slightly.