Optimasi pengeringan lapisan tipis simplisia temu putih dan temu lawak berdasarkan analisis eksergi

Abstract

Temu putih or zedoary (Curcuma zedoaria Rosc.) and temu lawak or java turmeric (Curcuma xanthorrhiza Roxb.) are two of some important medicinal plants in Indonesia. The dried slices of their rhizome are called simplicia and used as raw materials for jamu or traditional herbal medicine. The aim of this research were (a) to study the influence of drying process conditions on simplicia drying characteristics, quality and exergy eficiency during the drying, and (b) to determine the optimum process conditions to get the best quality. In the first study, the influence of drying air temperature, relative humidity (RH) and flow rate on the thin layer drying of temu putih and temu lawak slices were investigated. A laboratory air dryer was designed and used for drying experiments. The system was operated in an air temperature range of 40–70o C, relative humidity range of 20–80% and air flow rate 0.2-0.9 m/s. Three mathematical models available in the literature were fitted to the experimental data. It was found that drying of temu putih and temu lawak took place in the falling rate period. Higher drying air temperature and flow rate and lower drying air relative humidity resulted in a lower final moisture content and shorter drying time. By statistical comparison of the three models, it was concluded that the Page model represents drying characteristics was better than the other equations for describing single layer drying of both temu putih and temu lawak. In the second part, the effects of drying conditions on shrinkage and quality of temu putih and temu lawak were studied. A thin-layer dryer with machine vision system and image analysis software were used. Temu putih and temu lawak slices were dried at temperatures of 50, 60 and 70 oC and relative humidities of 20%, 30% and 40%. Changes in area of the slice were measured continuously during the drying. Shrinkage showed almost linear relation with moisture content. It was found that air temperature and relative humidity had no significant effect on shrinkage. Slices dried in a higher temperature showed more bend than a lower one. Lower drying air temperature resulted higher quantity of curcumin of temulawak and worse visually performance of sample. The last part was concerned with the energy and exergy analysis of the thin layer drying process of temu putih and temu lawak at different air temperatures and humidities using a laboratory dryer. Using the first law of thermodynamics, energy analysis was carried to estimate the amounts of energy gained from air drying and the ratios of energy utilization. Exergy analysis was accomplished to determine exergy destroyed and exergy efficiencies during the drying process by applying the second law of thermodynamics. The optimum process conditions for temu putih drying were at a temperature of 50 oC 20% RH and air flow rate of 0.2-0.3 m/s, while for temu lawak drying were at a temperature of 50 oC and 30% RH.