Gelation Temperature of a Gelatin Solution Determined by Diffusing Wave Spectroscopy

Diffusing Wave Spectroscopy (DWS) is a modern light scattering technique that is mainly utilized to probe the motion of particles in colloidal media. A microrheological analysis of the particle motion may further provide the medium’s rheological properties, namely the frequency-dependent storage and loss moduli, G’(ω) and G’’(ω), respectively. DWS can be applied to a rich variety of soft-matter systems, including gelling systems. In particular, DWS is able to accurately characterize their gel point, defined when the normalized intensity correlation function (ICF) no longer decays to zero. Gelatin solutions (Figure 1a) are dispersions of biopolymers in water that form physical gels below the gelation temperature Tgel (Figure 1b). Furthermore, at the gelation temperature of polymeric gel-forming liquids, G’ ~ G’’ ~ ω, where 0.19 < n < 0.92. In this application note, we propose to determine Tgel of a food grade gelatin solution using the DWS RheoLab from LS Instruments.