What do stirred yogurt microgels look like? Comparison of laser diffraction, 2D dynamic image analysis and 3D reconstruction

Abstract

Abstract Stirred yogurts can be considered as concentrated dispersions of microgels. The size, shape and fractal dimension of these microgels are known to have a direct impact on textural and sensory properties of stirred yogurts, consequently their thorough characterization is of interest. Different techniques can be used including laser diffraction (LD), 2D dynamic image analysis or 3D reconstruction from z-stack confocal images. The aim of this study was to compare the ability of the three techniques to describe the size, shape and fractal dimension of the stirred yogurt microgels. Two stirred yogurts with different compositions, one fat free (0.1%) and one high fat (9.3%), were used. The microgel size distributions obtained were similar using LD, 2D image analysis and 3D reconstruction. Additionally, 2D image analysis and 3D reconstruction enabled visualization of the microgels and access to their shape through morphological factors such as roughness index. The microgels observed were non-spherical, rough and heterogeneous in shape. All three techniques also made it possible to determine the fractal dimension of the microgels, but 2D image analysis displayed lower values than LD and 3D reconstruction.