Modelagem da transferência de massa unidimensional na desidratação osmótica de frutas considerando o encolhimento

Abstract

Osmotic dehydration is an operation used to partially remove water from foods such as fruits and vegetables. Several factors influence the process, such as the type of osmotic agent, solute concentration, solution temperature, exposure time, suspension, size, shape and compacting of the material. A tool widely used to evaluate the dehydration process is mathematical modeling. In this work, numerical and computational tools were developed to describe unidimensional mass transfer process in osmotic dehydration of fruits. The characteristic kinetics of the process was performed using two types of mathematical models that use numerical solutions of the diffusion equation. In the first, the process parameters and product dimensions were considered constant; in the second, it was admitted that these quantities are variable. For this, a diffusion equation was discretized using the finite difference method. The developed solutions were validated by comparison with results provided by analytical solutions and with experimental data available in the literature. In addition, to estimate the physical parameters of the mass transfer processes, was solved an optimization problem whose objective function is the Sum of the Square of Residues (SQR) between the simulated values and the experimental data. The tests indicated that the optimizer is able to obtain the parameters necessary for the study of this work, reaching the region containing the optimal values for the parameters. From the data obtained from the literature, optimizations were performed in order to obtain expressions to describe the effective water diffusivity. The results obtained for the diffusivities of water are in agreement with the literature. The results obtained through mathematical models, considering variable mass diffusivities and shrinkage proved to be a better match to the experimental data.