Modeling of mass and heat transfer during combined processes of osmotic dehydration and freezing (Osmo-Dehydro-Freezing)

A successive mass and heat transfer modeling approach was developed to describe the Osmo-Dehydro-Freezing (ODF) process. The dehydration process was described by an osmotic diffusion model based on mass transfer through cellular membranes and the diffusion of different species through intercellular spaces. Modeling of the freezing step was carried out by means of a numerical method, which includes the phase change phenomena in thermal balance equations through the value of enthalpy. Thus, the equations were solved in the whole system as if it were constituted by a single phase. As a result, the balance was transformed into a transient problem with temperature dependent properties. The simulation of the ODF process was successfully validated with experimental results obtained on tomato cubes (R2=0.997–0.999; RMSE=0.156–0.252). The predicted temperature profiles almost coincided with experimental data. This was not the case with a selected, regularly used empirical model, which was used for comparison reasons. The prediction deviations of the tested empirical model were not only large, but they were constantly and significantly increasing with increased dehydration times.

► A new methodology was developed to describe Osmo-Dehydro-Freezing (ODF). ► The proposed model was not empirical but was based mainly on structural data. ► The proposed model allowed accurate prediction of temperature and phase changes. ► The proposed model allowed accurate prediction of solute and water concentrations. ► The model presents excellent prediction ability in contrast to an empirical model.