Mass transfer modeling of equilibrium and dynamic periods during osmotic dehydration of radish in NaCl solutions

Abstract

Equilibrium and dynamic mass transfer properties of water and solute were investigated during osmotic dehydration (OD) of radish slices in sodium chloride (NaCl) solutions. OD experiments were performed in 0.05, 0.15 and 0.25g/g solutions at different temperatures (25, 40, 55 and 70°C) using a brine-to-vegetable mass ratio of 15:1. An analytical solution for unsteady-state mass transfer based on Fick's second law of diffusion was used to mathematically describe water loss and solute gain curves and for the simultaneous estimation of diffusion coefficients and final dehydration–impregnation levels in product. Under such experimental conditions, effective water diffusivity was in the range of 1.85–2.74×10−9m2/s, whereas solute diffusivity values were between 0.74×10−9 and 2.88×10−9m2/s. Corresponding dehydration and impregnation levels of radish at equilibrium were estimated between 0.25 and 0.81gwater/g fresh product and 0.01–0.11gsolute/g fresh product, respectively. As demonstrated, current results may be applied to determine the set of conditions (process time, brine concentration and process temperature) yielding an osmodehydrated radish product within given specifications.