Design and Development of Compact Spouted Bed Roaster for Coffee Beans and its Performance Evaluation.

Roasting is one of the important unit operations where in the grains are exposed to a
heating process to remove the free and bound moisture present in them. Moisture removal
accompanied by chemical reactions during this process brings about important physicochemical
changes (color, volume, mass, density and volatile compounds). These changes
also have a bearing on the shelf life and organoleptic properties of the product. Since
uniformity in roasting is an important criterion, distribution of heat equally to all the food
grains is of paramount importance. Therefore apart from heating, method/s of mixing the
grains also assumes importance. Thus roasting becomes a thermo-mechanical operation.
Conventionally, roasting is practiced in many ways such as sand roasting,
conduction type drum roasting which are characteristic of the longer roasting time, non
uniformity of products and smoky and acrid taste. Solid-gas contacting method in fluid bed
roasters and spouted bed roasters is of late being used to achieve product uniformity. In
view of the advantages of convection heat processing of particulates like coffee beans and
the non availability small scale units, it was proposed to develop a compact, laboratory scale
spouted bed roaster and evaluate its performance.
Coffee bean is selected for studies under this project and its engineering properties
were determined. Based on the critical design parameters, detailed design of the compact
spouted bed roaster was designed. Product design principles were adopted to optimize the
compact model. Based on the design drawings, a prototype of Compact Spouted Bed
Roaster (CSBR) was fabricated using economical and efficient manufacturing process.
In order to validate CSBR for roasting coffee beans, studies were conducted with
wide range of operating conditions. Temperature of hot air ranged between 200 to 250°C
and the residence period in the roaster was varied in the range of 6.5 to 19 min.
Considering the overall product quality, hot air temperature of 230°C and residence time of
13 min was found to be optimal. The unit also was tested for other grains like corn,
groundnut etc and was found to work satisfactory.