Development of clove buds drying process for small to medium enterprises

Abstract

Clove essential oil (EO) has a high eugenol content. Fresh cloves need to go through a drying and distillation process to produce essential oils. However, sun drying cannot be done optimally during the rainy season, so some farmers use the oven drying method. The initial study found that the eugenol content after the drying process decreased by 17%–20%. Therefore, his study has four successive objectives to maintain high eugenol content in dry cloves. The first objective is to identify factors that are affecting the eugenol content of the clove buds during the drying process. The second is to propose a modification drying model by combining various parameters. Next, to design and develop a drying apparatus to keep eugenol levels in clove buds high. And the fourth objective is to fabricate the prototype drying apparatus on the lab scale. After the problem was identified, the problem was solved using two methods, first theoretically through a combination of existing formulas, second through the TRIZ method, and continued research for a new oven prototype. The theoretical method showed that the porosity in the clove pile can affect the drying process. Hence, in the theoretical method, a formula was found to determine the thickness of the clove pile. The theoretical method also found several parameters to be a reference in designing a new oven, namely the number of trays in the oven (4, 5, 7, and 10), clove thickness (1, 1.5, 2, and 2.5 cm), the space between the trays in the oven, and steam gap on the tray (1–3 cm). In addition, it can also determine the appropriate oven coating material (plywood, galvanized plate, and air). In the TRIZ method, several solutions were found to design a new oven. Eight things have been changed from the existing drying oven, including; the number of trays in the oven, a steam gap in each tray, the size of the mesh used for the tray base, material for the drying oven, the thickness of the cloves on the tray, the temperature used in the drying process, installation of a thermostat to control the temperature in the oven, separate combustion chamber from tray space (indirect heating), and without using a blower. Several parameters were adjusted in the experiment using a drying oven prototype according to the theoretical calculation results and the TRIZ method results. In researching the new prototype oven, five parameters were used to get optimal results. These five parameters were obtained from the solution using the TRIZ method, namely temperature, the thickness of the pile of cloves, steam gap, size of the mesh tray, and the distance between the trays. Optimization using Response Surface Methodology (RSM) was divided into two stages on three responses: drying rate, eugenol content, and energy. From the results of optimization and verification in the first stage, it was found that three factors; temperature (70 °C), thickness (1 cm), and steam gap (3 cm), gave appropriate results (error below 5%) for the three responses (drying rate, eugenol content, and energy). Then, from the results of optimization and verification in the second stage, it was found that three factors; temperature (74 °C), a mesh of tray (10 mesh), and space of tray (12 cm) also gave appropriate results (error below 5%) for the three responses (drying rate, eugenol content, and energy). In conclusion, the new oven design based on theoretical calculations and the results of the TRIZ method can produce dry cloves which have eugenol content above 70%.