Glassy dynamics of gelatin gels

We measure the elasticity of thermoreversible gelatin gels during slow cool and heat cycles, with and without stops. The responses are measures of the system energy, since elasticity is a function of the helix fraction, which quantifies the system's order. They show the same memory and rejuvenation effects as magnetic spin glasses. At constant temperature, all gels reach an aging regime, where their responses decrease linearly in log(time), like many other glassy systems. Complex memory effects occur after temperature jumps. We suggest that the parallels between gelatin gels and other glassy systems are due to their temperature-dependent, rugged, hierarchical energy landscapes. Gelatin gels act rather like "colloidal spin glasses''. However, unlike magnetic spin glasses, their size and time scales should allow experimental measurement of the relation between mesoscopic dynamics and macroscopic behaviour.