Effect of Shrinkage on the Effective Diffusivities of Water andSucrose during Osmotic Dehydration of apple cylinders

The water and sucrose effective diffusion coefficients were estimated in apple cylinders during osmotic dehydration in sucrose solution at three different concentrations of 30, 40 and 50% andtemperatures of 30, 40 and 50°C .The solution to sample mass ratio was more than 20:1 (w/w) andthe process duration varied from 0 to 6 hr. A mathematical model developed by Azuara was used for describing the mass transfer in osmotic dehydration of apple cylinders. The effect of changes in the volume of apple cylinders during osmotic dehydration on the kinetics of moisture diffusion were studied. The experimental drying curves were adjusted to the diffusional model of Fick’s law for infinite cylinder with and without consideration of shrinkage to measure water and sucroseeffective diffusivities.The effective diffusivities without shrinkage ranged from 1.59 ×10-10 m2/s to 2.49 ×10-10 m2/s and with considering shrinkage varied from 1.41 ×10-10 m2/s to 2.28 ×10-10 m2/s. The values of effective diffusivity obtained by considering the samples shrinkage were smaller than those calculated without considering shrinkage

Keywords:

Osmotic dehydration , Effective diffusivity , Shrinkage , Apple cylinders