Abstract
The aim of this study was to investigate the vapor pressure measurement method of foods at sub-zero temperature to
understand the process of drying of foods in frozen storage. Bovine serum albumin (BSA) was used as a sample in
this study. Freeze-dried (FD) BSA and heat-denatured (HD-FD) BSA were also prepared for the measurement.
Further, a humidity probe that can function at sub-zero temperature was added to the prepared measurement system.
The vapor pressure of the BSA samples was measured at 25°C and –18°C. The moisture adsorption isotherm of
BSA obtained at –18°C was similar to the one at 25°C. Moreover, the water vapor pressure of the samples at
sub-zero temperature showed the same behavior as at 25°C. The moisture adsorption isotherms of FD and HD-FD
samples also exhibited the same characteristics as those of the BSA. Therefore, a basic method can be devised to
explain the drying mechanism of frozen foods by combining the results of this study.
