Dynamics of water and hydrated gelatin in partially crystallized mixtures

Abstract

Gelatin-water mixtures with gelatin concentrations in a range of 10 – 40 wt% were investigated by broadband dielectric spectroscopy measurements in wide frequency (1 mHz – 50 GHz) and temperature (113 – 298 K) ranges. Three dielectric relaxation processes were observed. The temperature dependences of the three relaxation processes observed for the gelatin-water mixtures are similar to those observed for the BSA-water mixtures. The fastest relaxation process is originated from the uncrystallized water (UCW) in hydration shell and its relaxation time is the same to that of the UCW in various uncrystallized binary water mixtures. The intermediate relaxation process is originated from ice and its temperature dependence of the relaxation time and strength resemble pure ice relaxation process especially above 240 K. The slowest relaxation process is originated from hydrated gelatin. The strength of the slowest relaxation process is large, and it is similar to that of the relaxation process of hydrated BSA. The characteristic property of the gelatin-water mixture is the change of the temperature dependences of the relaxation times of the UCW and hydrated gelatin at around 260 K, above which the melting of ice occurs.