Study of Heat Transfer and Product Characterization in Spouted Bed Coffee Roaster

Abstract

Roasting is one of the essential coffee production processes, which significantly influences the quality of roasted coffee. There are many approaches for roasting, applying rotating cylinder (a standard method of the roasting process), fixed bowl, and fluidized bed method. A study of heat transfer and product characterization was conducted in a spout fluidized bed coffee roaster with a 2000-gram capacity. In this research, Temanggung Robusta Coffee beans were processed with two different operating temperature settings, performing 225°C for a low-temperature long time (LTLT) and 240°C for a high-temperature short time (HTST). At both operating temperatures, the overall heat transfer coefficient for coffee roasting was 26,63 – 92,02 W/m2K for the LTLT process and 44,85 – 139,98 W/m2K for the HTST process. The products, then, were analyzed for moisture and ash content. The results showed that a low-temperature long-time process resulted in lower moisture content. Furthermore, there was no significant difference in ash content compared to the high-temperature short-time process (HTST).