This work presents a new technique of passive microrheology for the study of the microstructure viscoelastic properties and the gel point transition for polymers and hydrogels. Passive microrheology consists of using micron sized particles to measure the local deformation of a sample resulting from the thermal energy, that is to say the Brownian motion. Our technique is based on Diffusing Wave Spectroscopy. It consists of Dynamic Light Scattering (DLS) extended to an opaque media. The determination of the Mean Square Displacement (MSD) curve enables to characterize completely the viscoelastic properties of a sample. The technique allows to measure particle displacement, which is directly related to the sample’s viscosity and elasticity. (Bio-)polymers have been introduced to a large scale of formulation not only in the food sector. Their unique properties in stabilization, structuration as well as texturation made them to one of the most used components. Especially the gel formation capacity is of outmost interest. This work presents a rescaling data processing known in rheology as time-curing superposition (1-3), to determine precisely the gel point transition and gel strength parameters according to the Winter-Chambon-Criterion. Results will show the determination of the gel point versus time yogurt formation, gel point versus temperature for carrageenan dispersion and gel point versus concentration of cross-linker for two composites systems. References 1. H. H. Winter and F. Chambon, J. Rheol. (1987) 2. D. Adolf and J. E. Martin, Macromolecules (1990) 3. T. H. Larsen and E. M. Furst, PRL (2008)