Drying indigenous agriculture product by using fluidized bed dryer / Siti Azeeyatul Akmar Kemat

Herbal plants such as lemon grass, ginger and laksa leaf have been commonly used as condiments in food industry and also used traditionally as medicinal product. In the processing of herbal products, drying has been used to preserve the plants. In this study, drying of lemon grass, ginger and laksa leaf has been carried out in a Fluidized bed dryer at 30°C to 100°C with hot air velocities of 1.09 m/s, 0.98 m/s and 0.87 m/s. Different bed height of 1 cm, 2 cm and 4 cm have been filled up with the herbs in the fluidized bed. From the microstructures of the herbal plants which were obtained from Scanning Electron Microscope, higher temperature and hot air velocity that have been used to dry the plant do affect their microstructures. The boundaries between the cells disappear, distorted and rupture. However, shorter drying time maintained the cell boundaries. Laksa leave produces the least destruction of the microstructure compared to lemon grass and ginger. Quality of the dried herbal plants has been determined through color changes and in terms of green and yellow color, ginger has the highest value. The result also showed that temperature and bed depth of sample have insignificant influence in the color degradation of the sample. Drying the herbal plants in the fluidized bed dryer maintained all the chemical constituents such as citral, neral and geraniol in lemon grass, gingerol in ginger and decanal and dodecanal in laksa leaf. From Response Surface Method (RSM), the optimum drying condition for lemon grass and ginger was at bed height of 2 cm, 80°C and hot air velocity of l.OOm/s. Meanwhile, for laksa leave, the optimum drying condition was at 2 cm, 51°C and 0.94 m/s. This study has also shown that drying rate of the three herbal plants increased as the temperature of the air increased. It has been observed that drying process took place in the falling rate period. Suitable models to describe the drying behavior of lemon grass, ginger and laksa leaf have been evaluated. It was found that for lemon grass, ginger and laksa leaf, the suitable models were Midilli and Kucuk (Midilli and Kucuk, 2003) and Modified Henderson and Pabis (Karathanos and Belessiotis, 1999).