Abstract:
Coffee roasting is one of the. most important stages in processing drinking coffee to enhance flavours, and ease grinding. It is a process of pyrolysis (time temperature dependent) which, by increasing the temperature of the coffee from room temperature to 180°C and above, brings about marked physical and chemical changes in the beans that improve the quality of coffee and make it easier to prepare.
The purpose of this study was to design and construct a coffee roaster machine for helping coffee farmers improve-on the quality of their products (roasted coffee) which would yield high market prices hence improving their economic wellbeing and this was achieved by roasting under controlled time and temperature conditions in order to reduce loss of desired aromas to the environment and attain uniform roasting of the beans.
The design of the various machine parts was earned out by analysing forces acting on them. Force analysis led to selection of proper materials to withstand the forces to avoid failure. Stainless steels of various grades were the main materials recommended to be used because they are food grade, strong and durable, Engineering-drawings of the various components were drawn before the various components were constructed and then, machine parts fabricated. A fully functional prototype resulted after all the above operations. Testing of the prototype was carried out and the figures revealed that the machine was 75.0% efficient, the coffee roaster has a total cost of 1,417,000 UGX which includes all the taxes, cost of material, machinery and hired labor to construct the machine plus overhead costs. The cost-evaluation analysis of the project was based on the payback period method, the project was evaluated to breakeven in 1.23 years and on net present value method with NPV of 1, 000,739' UGX over a period of five years.
