Integration of the Various Scales: The Example of Hydrophobic Dense Edible Coatings

Abstract

In the previous section, we presented the studies that have tentatively described and formalized (i.e., modeled) the relationship between structural and mass transfer properties in food. We pointed out that, in food science, the relationship between structure and transfer is rarely quantified and modeled. This illustrated well the complexity of the food materials and the difficulty of investigating in situ and in real conditions of use or storage the evolution of food structure. The scarce relationships established between structural and mass transfer properties were done at only one scale of observation, without any integration of the multiscale structure of the product. However, this multiscale structure is responsible for the main mechanisms governing mass transfer. For example, the structure at a molecular or macromolecular scale governs the local diffusion of gas or vapor, which is also affected by the nanoscale (presence of impermeable particles that increase the tortuosity of the matrice) and by the macrostructure of the product (multilayered structures). Most of the time, diffusion is characterized at a macroscopic scale by measuring an overall apparent diffusion coefficient. The apparent diffusion coefficient is a macroscopic property and cannot describe the different mechanisms of migration that prevail in food. A multiscale analysis of the relationship between the structure and mass transfer properties is thus required. Some attempts at multiscale analysis were carried out on lipid-based edible coatings used as moisture barriers, probably because of the relatively simpler structure of these dense materials, as compared with biological products or other foodstuffs. This section is devoted to the description of these attempts.