Mathematical Modeling of Mass Transfer During Osmotic Dehydration of Cylindrical Green Bean

In this study, mass transfer during the osmotic dehydration of cylindrical cut green beans in salt solution was investigated. The osmotic salt solution concentrations used were 10%, 20% and 30% NaCl, and osmotic solution temperatures were 30ºC and 50 ºC, fruit to solution ratio was lower than 1:20 (w/w) and the process duration varied from 0 to 6hr. A two-parameter mathematical model was used for describing the mass transfer in osmotic dehydration of green bean samples and estimation of equilibrium moisture loss and solid gain. Effective radial diffusivity of water as well as solute was estimated using the analytical solution of Fick's law of diffusion in the cylindrical coordinates. For above conditions of osmotic dehydration, the effective diffusivities of water and solute were found to be in the range of 1.77610-10–2.70710-10 m2/s and 1.12610-10–1.66710-10 m2/s, respectively. Average moisture and salt concentrations as a function of time and also moisture and solute distributions as a function of time and location in the radial direction were plotted by using the estimated equilibrium moisture and solute concentrations and also moisture and solute diffusivities. Moisture and solute distributions show that the change of moisture and salt is mainly confined in the region of the surface and slowly progresses to the interior.