Rehydration Modeling of Food Particulates Utilizing Principles of Water Transport in Porous Media

Rehydration is related to the amount of water or other medium that a dry food absorbs during a process, and it is associated with the kinetics of the medium uptake. Water imbibition theory has a multidisciplinary validity, and has applicability in modeling the rehydration of dried porous food. Imbibition follows the general Lucas–Washburn equation. However, its utilization has highlighted the need for model improvement to overcome several discrepancies related mainly to the utilization of a single effective cylindrical capillary radius and a constant contact angle. Basic theory of flow in porous media is widely utilized in several other domains (e.g., petroleum, chemical engineering) and plays a cardinal role in soil physics research. Because of the central role of soil water in agricultural systems, modeling of soil porous media, water flow, and mass transport has been promoted in interdisciplinary research and quantification. This multidisciplinary approach has also recently motivated a few studies on bridging of food science and soil physics, showing its high potential and providing insights into the mechanism(s) governing water and other liquid uptake by dry food particulates. Analogous to a food sorption isotherm, the water characteristic curve of a porous media describes the functional relationship between water content and a matric potential under equilibrium conditions. This curve is an important property related to the pore size distribution and space that are strongly affected by texture and structure, as well as other related factors, including organic matter content. Continuous retention curve (RC) functions are needed in order to solve the flow equations. Numerous well-known empirical functions such as Brooks and Corey and van Genuchten have been developed. Utilization of porous media theory for modeling of food rehydration requires employment of a characteristic curve, which is time consuming and cumbersome. Bridging between sorption isotherms commonly utilized in food science with water characteristic curves employed in soil physics could furnish a novel and integrated approach paramount to overcoming some of the complexity that hampered previous attempts. This could lead to new avenues for studying and optimizing food rehydration. The overall objective of this chapter is to depict current understanding of the rehydration process, and to highlight how a new approach derived from soil physics and porous media theory could be utilized for foods.