OSMOTIC DEHYDRATION OF FOODS: MASS TRANSFER AND MODELING ASPECTS

Abstract

Biological materials contain a variety of individual soluble components. When cellular biological materials are immersed in osmotic solution, multicomponent mass transfer occurs, which ultimately leads to the loss of water from the food, or osmotic dehydration. Mass transfer of food constituents during osmotic dehydration may cause changes in food quality in terms of nutritional value, texture, color, and taste. The aspects that are important for mass transfer modeling are the driving force and the physical properties of cell units and tissue matrix of cellular material. The complex cell wall structure of cellular material acts as a semipermeable membrane, resulting in two simultaneous and countercurrent flows in the biological tissue: water transfer out of material tissue and transfer of the solute from the osmotic solution into the cellular tissue. When the cells remain intact, the chemical potential of water is the main local driving force for mass transfer towards the free intercellular spaces. At the same time, volume changes in the cellular tissue occur throughout the process after immersion in osmotic solution. Diffusion, osmotic processes, flux interactions, and tissue shrinkage should all be taken into account for accurate description of the mass transfer phenomena during osmotic dehydration. The mass transfer process has been modeled based on the theories of Fickian diffusion, irreversible thermodynamics, multicomponent diffusion, and hydrodynamic flow. The use of vacuum or pulsed vacuum has an effect on mass transfer, which reveals the effect of material structure property on mass transfer. Evaluation of the long-term equilibrium and the distribution of the phases in the tissue provide a better understanding of the phenomena that control the mass transfer processes in osmotic dehydration. It is important to link microstructural investigations with the processing parameters during osmotic dehydration, and the compositional and mechanical characteristics of the tissues. Knowledge of the structural characteristics of the materials and the relationship between all components in the mass transfer process needs to be further understood.

Keywords:

• Fickian diffusian
• Irreversible thermodynamics
• Mass transfer
• Matrix
• Modeling
• Multicomponents
• Shrinkage

Acknowledgments