High-Pressure Effects on Gelatin Sol–Gel Transition
Nikolaos A. Burger, Gerhard Meier, Dimitris Vlassopoulos, Benoît Loppinet
Abstract
High Resolution Image Download MS PowerPoint Slide We investigated the effects of high hydrostatic pressure on the sol–gel transition of gelatin dispersions. We used dynamic light scattering (DLS) and DLS-based passive microrheology to monitor the evolution of the viscoelasticity during isothermal gelation. It provided easy identification of the sol–gel transition and the isothermal critical gelation time ( t c ) and values of viscosities of sols and shear modulus of gels. At a given temperature, t c decreased with increasing pressure. Up to 100 MPa, the temperature dependence of t c followed the established empirical rule t c ∼ ( 1 − T T C ) n and the critical temperature T c increased with pressure by ∼0.04 K/MPa. The critical gelation time scaled with the quench depth T – T c or equivalently with the distance from the pressure-dependent collagen denaturation temperature (∼314 K, at 0.1 MPa), which also increases by ∼0.04 K/MPa in the first 100 MPa. The pressure dependence also reflected on the time evolution of the intrinsic viscosity, η i, or elastic modulus, G p, in the sol or gel state, respectively, are reported. Both η i or G P evolution speeds up with pressure. Finally, using a reverse quenching approach, we observed a slowing of the gel melting when the pressure increases. Our results confirmed that the rheological evolution reflects the helix formation process and that pressure stabilizes the helices.