The design, manufacture and evaluation of a drum coffee roasting machine had been carried out. The aimed of the study was to develop a small-scale drum roaster to meet the demand of the small enterprises at design and function. The development stage consisted of sizing of the main components, creating technical drawings, determination of component materials, manufacture and performance test. The dimension of the roaster drum was 168.28 mm in diameter and 250 mm in length; the capacity of the roaster was 750 gram/ batch. Results of the test determined that the coffee roasting machine had worked well as expected. The preheating time was 15-22 minutes at a drum speed of 67.5 rpm. The initial loading temperature was 180°C. The test using arabica coffee bean reveals that the average crack time was 8.78 minutes, development time was 2.35 minutes, decreasing mass and increasing volume ranged from 19.80 – 20.30 % and 49.97 – 54.85 % respectively. The average crack time of Robusta coffee bean was 10 minutes; development time was 3 minutes, decreasing mass and increasing volume ranged from 10.87 – 14.90 % and 44.93 – 56.20 %, respectively. The required time to roast Arabica green coffee bean to the light-medium and medium-dark level was 11.3 and 12.38 minutes respectively, besides for Robusta green coffee beans was 13.00 and 14.00 minutes respectively.
The changes in physical, mechanical, and colours after roasting in two-level were investigated. Aims of this study were to evaluate changes in the physical, mechanical, and colours due to the roasting process of the Arabica and Robusta coffee bean grown in Cisalak Sub-District, Subang District-West Java. Results of analysis determined that the roasting process resulted in decreasing the moisture content of green coffee bean from 13.8% to 6,54% of first-level roasted bean and 6.24 of the second-level roasted bean, while that of robusta decreased from 11.22% to 7.56 and 6.12%. First-level roasting was categorised as a light roast, while the second-level was a medium roast. The Roast Weight Loss of arabica and robusta from green to light roast bean were 19.45 % and 16,24%, respectively, and that to medium roast bean was 26.20% and 22.37%, respectively. The roast volume change of arabica and robusta from green to light roast bean were 50.55% and 44.30 % respectively, and that to medium roast bean were 54.65% and 55.92 % respectively. The total colour differences between green with light and medium roast bean of arabica were 6.39 and 2.52, while that of robusta were 6.19 and 2.49, respectively.
Traditional fermentation process usually takes a long time and hard to achieve and maintain the optimum temperatures condition. The controlled fermentation process can be done using a fermentor for conditioning the temperature at the beginning of the process as bacteria and yeast can develop optimally at certain temperatures. However, traditional heaters that utilize heat transfer by conduction and convection have not been able to homogenize the temperature of products so that the fermentation process is not well controlled. Heating technology that has great potential to produce fast and uniform heating is by using ohmic technology. This research aims to design and to conduct a test of ohmic-based fermentor model. Methods used in this study were a functional and structural analysis of fermentor design and performance test of the fermentor model. The test was conducted using two materials as the heated product (0.02 M NaCl solution as a liquid product and soybean as a non-liquid product) with three variations of voltage treatment (110, 165, and 220 V). Design of the ohmic-based fermentor model had been constructed and tested. Analysis of alternative methods, types, and ohmic fermentor material has been carried out as a reference in designing. Test results showed that the fermentor had been proven to be able to maintain, control, and monitor the temperature in the reactor in real-time. The energy efficiency achieved a high value of 81.96% up to 86.29%. The temperature distribution in the fermentor was also determined uniform for both liquid and non-liquid products with the average value of 40.01±0.16°C (the reference temperature is 40°C). It was indicated that the fermentor model can be used for further fermentation test using various products.
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