Optimization of Drying Process of Rambutan by Combined Method of Osmosis Ultrasound and Complementary Drying of Hot Air

Abstract

D rying of fruits has been considered as a way to improve the durability, and is one of the main methods which have been common for centuries. Unlike fresh vegetables which are kept only for a short period of time and in special circumstances, dried products can be kept a long time without reducing the nutritional value. Also, because of the low mass weight of dried fruits, they are easily and conveniently transported (Da Silva et al., 2017). The fruit used in this research for drying is Rambutan which is native to Southeast Asia, i.e., Malaysia, Indonesia and Thailand. In the Malay language, Rambutan means Abstract | Drying is widely known to be one of the common processes in the food industry to increase the shelf life of fruits and vegetables. Using osmosis-ultrasound before drying with hot air causes the preservation of nutrients in products and reduces heat energy to remove the produc water. In this study, after osmosis pretreatment, samples were put under an osmosis dehydration process. First, using Osmosis-ultrasound with 40.5% concentration in Sekanjabin solution then dried in an oven at a temperature of 70°C. The characteristics of solid gain, water and weight loss, shrinkage and rehydration were evaluated. The obtained results showed that by increasing the concentration of weight and water loss, solid gain increased. Accordingly, in a higher concentrated osmotic solution, the osmotic pressure, which is a key factor in mass transfer in the osmotic dehydration process, increases by increasing concentration, the percentage of solids gain increased; shrinkage and rehydration decreased. Conclusively, the drying of Rambutan by use of osmosis-ultrasound dehydration process when compared to osmotic dehydration, showed a significant decrease in the shrinkage of fruits resulting in rehydration, i.e., causing the percentage of solid gain, weight and water loss to be increased.

Mass transfer analysis and kinetic modeling of ultrasound-assisted osmotic dehydration of kiwifruit slices

“…The rehydration ratio of kiwifruit slices reduced from 204.1% to 158.8%, by increasing sucrose concentration from 20 to 40%. Similarly, Farooq, et al 32 reported that the rehydration ratio of Rambutan decreased with increasing osmotic solution concentration. Shekar and Javadi 33 observed a decrease in rehydration rate when using UAOD compared to control samples, and observed a greater reduction in UAOD samples than in osmotically dehydrated samples.…”