The industrial relevance of mass transport in dairy products is vast. While it is known that the microstructure of dairy matrices affects diffusion, the link between structure and diffusion has rarely been established and the properties of solutes were almost never considered. Our objective was to investigate the impact of the microstructure of different model cheeses on diffusion of solutes with different physicochemical characteristics. The diffusion of rigid and charged proteins versus flexible and charge - neutral dextrans of various sizes was studied in model cheeses obtained from ultra - or microfiltered milk. Diffusion coefficients were measured using the Fluorescence Recovery After Photobleaching technique. Structural parameters of the model cheeses we re quantified by low - temperature transmission electron microscopy coupled to image analysis. Solute diffusion was sensitive to the microstructure of the matrices, especially to the degree of aggregation of casein micelles, which depends on heat treatment a nd acidification level of the milk retentate. As expected, the diffusion greatly decreased as solute size increased but, more surprisingly, rigid and negatively charged solutes were much more hindered than the flexible and charge - neutral solutes. Besides t he obstruction effects generated by the matrix microstructure, the molecular interactions between the matrix and the solute could explain different diffusion behaviors