Broadband Dielectric Spectroscopy of Albumin‐Water Mixture in Frozen State

Broadband dielectric spectroscopy (BDS) measurements of 40 wt% bovine serum albumin (BSA)‐water mixture under frozen state were carried out in the frequency range of 20Hz to 1.8GHz in the temperature range of −70 to −4°C. Three relaxation processes were observed in addition to the low frequency electrode polarization and contribution of dc conductivity. The relaxation process observed in a frequency range higher than 1 MHz is due to the unfrozen water in the frozen BSA‐water mixture. The relaxation process due to ice was observed in the frequency range of 100 Hz to 10kHz. Another relaxation process, which was observed in the frequency range below 1 Hz at −70°C, shifted to higher frequencies with temperature increases and reached up to 1 MHz at just below the melting temperature. This highly thermal‐activated process is probably concerned with the molecular motion of BSA and/or ionic relaxation processes under frozen BSA‐water mixture.