Mass transfer during osmotic dehydration of celery stalks in a batch osmo-reactor

Abstract

In this study, dehydration behavior of bulk of celery stalks, during osmotic drying in a limited volume of salt solution, was investigated. Experiments were carried out in the three initial solution concentrations of 10, 18 and 25 % (w/w) and at the three temperatures of 35, 45 and 55 °C. The volume ratio of the fruit to the solution was considered 1:3. A two-parameter model was used for prediction of kinetics of mass transfer and values of equilibrium moisture loss and solid gain. Moisture and salt effective diffusivities in celery stalks were estimated by fitting the experimental data of moisture loss and solute gain to the analytical solution of Fick’s second law of diffusion. The analytical model was solved by defining a partition factor, K, assuming that the concentration of solute just within the surface of the material is K times that in the solution. Results showed that moisture and salt effective diffusivities and equilibrium values of moisture loss and solute gain increased with increasing the temperature and solution concentration. Results showed a good agreement between the two parameter model (with mean relative error of 4.016 % for moisture loss and 5.977 % for solid gain), analytical solution of Fick’s second law (with mean relative error of 8.924 % for moisture loss and 9.164 % for solid gain) and experimental data.