Glass transition of partially crystallized gelatin-water mixtures studied by broadband dielectric spectroscopy

Abstract

The glass transition of partially crystallized gelatin-water mixtures was investigated for gelatin concentrations of 40 and 20 wt. % by broadband dielectric spectroscopy (BDS) in wide frequency (10 mHz-50 GHz) and temperature (113-298 K) ranges. Three dielectric relaxation processes were clearly observed. The origin of each relaxation process was the same as that observed for partially crystallized bovine serum albumin (BSA)-water mixtures [N. Shinyashiki et al., J. Phys. Chem. B 113, 14448 (2009)]. The relaxation process at the highest frequency is originated from uncrystallized water (UCW) in the hydration shell of gelatin. Its relaxation time is almost the same as that of water in uncrystallized system; water in various binary aqueous mixtures and confined water in nanoscale region. The relaxation process at the intermediate frequency is originated from ice, and its relaxation time and strength were similar to those for the relaxation of pure ice, particularly above 240 K. The glass transition temperature Tg, is defined by BDS measurement as the temperature at which dielectric relaxation time τ, is 100-1000 s. The relaxation process at the lowest frequency, Tg is approximately 200 K, is originated from the cooperative motion of water and gelatin. This relaxation is strong and has a similar relaxation strength to that of hydrated BSA. At Tg for the relaxation process involving the cooperative motion of gelatin and water, the temperature dependence of the relaxation process of UCW crosses over from Vogel-Fulcher behavior to Arrhenius behavior with decreasing temperature. A characteristic property of the gelatin-water mixture is a change in the temperature dependence of the relaxation time of the relaxation processes of hydrated gelatin at approximately 260 K.

Dielectric study on temperature–concentration superposition of liquid to glass in fructose–water mixtures

“…The relaxation time and strength of the β relaxation change from having weaker temperature dependences below T g to having stronger ones above T g . These changes in the behaviors of the β relaxation upon crossing T g are the same as those found for the ν relaxation [9,10], which is the primary relaxation process of water originating from the local motion of water molecules in various other aqueous mixtures with hydrogen-bonded molecular liquids, polymers, and nanoporous systems [9][10][11][12][13]. The properties of the relaxation time, τ β , and relaxation strength, Δε β , of the secondary β relaxation above and below T gα for fructose-water mixtures of all concentrations have been found to be the same as those of the ν relaxation observed in aqueous systems and the JG relaxation observed in binary mixtures of van der Waals liquids.…”

Applying Broadband Dielectric Spectroscopy (BDS) for the Biophysical Characterization of Mammalian Tissues under a Variety of Cellular Stresses

“…We observe that relaxation II has similar activation energy with ice Ih at low temperatures, while relaxation I exhibits a slightly lower activation energy. In addition, data analysis reveals that the dielectric strength of relaxation II is rather high, Δε~30, comparable with the dielectric strength of the ice phase in bulk [33,34], while relaxation I has smaller dielectric strength (Δε~1–3). Therefore, we attribute relaxation II to the ice Ih phase whereas (the faster) relaxation I may be related with polarization in the disordered liquid-like surface layers of the ice crystallites [35].…”

“…Therefore, we attribute relaxation II to the ice Ih phase whereas (the faster) relaxation I may be related with polarization in the disordered liquid-like surface layers of the ice crystallites [35]. The fact that the time scale of relaxation II shows different temperature dependence than those of bulk hexagonal ice has also been observed in other hydrated systems and reflects, actually, the great sensitivity of the dielectric properties of ice crystallites on their defects and on the impurities that are incorporated in their lattice [34,36]. It is interesting that all of the tissues exhibit relaxations I and II with similar characteristics.…”

Heterogeneous Solvent Dielectric Relaxation in Polymer Solutions of Water and Alcohols

“…This crossover has been discussed based on the observations of water dynamics over an extremely wide range of relaxation times and viscosities. The non-A-A crossover of water dynamics has been observed in various types of aqueous systems, such as aqueous solutions of alcohols, ethylene glycol (EG) oligomers, sugars, polymers, and protein and porous systems those contain water [3,[5][6][7][8][9][10][11]35]. The temperature dependence of the relaxation process of water in these systems changes at a certain temperature, which is called the crossover temperature, T c , in this paper.…”