Some advances in osmotic dehydration of fruit

There are many works in the field of osmotic dehydration of fruit where kinetic studies using a macroscopic approach are reported. However, very few studies have been developed from a microscopic point of view, taking into account the compartment structure of the cellular tissue and the complex cell to cell transport phenomena. The latter could allow a better understanding of the process and therefore a more accurate model, but in many cases it is not possible to establish an adequate bridge between microscopic models and practical applications. The analysis of the concentration profiles during mass transfer phenomena in structured foods, being a macroscopic approach, is a very useful tool to clarify the mass transfer mechanisms as well as to calculate the corresponding kinetics. In this paper the concentration profiles of water and solutes, developed throughout the fruit osmotic dehydration, are discussed as a function of the temperature and sample thickness for apple. The profile development is modeled in terms of a new mathematical model, which could avoid some of the restraints of the Fickian equations, usually utilized in this kind of modeling. Another aspect involved in this work is the equilibrium status of the fruit in the osmotic process. Equilibrium data are required to evaluate the true driving force of the mass transfer process. Nevertheless, a lack of studies in this area was detected. The results of extensive work on the behavior of samples until equilibrium is reached in osmotic treatments are also discussed.