title: Effects of Pressure-shift Freezing on the Structural and Physical Properties of Gelatin Hydrogel Matrices.
abstract: This study investigates the effects of the gelatin concentration (10-40%, w/v), freezing temperatures (from -20℃ to -50℃) and freezing methods on the structural and physical properties of gelatin matrices. To freeze gelatin, the pressure-shift freezing (PSF) is being applied at 0.1 (under atmospheric control), 50 and 100 MPa, respectively. The freezing point of gelatin solutions decrease with increasing gelatin concentrations, from -0.2℃ (10% gelatin) to -6.7℃ (40% gelatin), while the extent of supercooling did not show any specific trends. The rheological properties of the gelatin indicate that both the storage (G') and loss (G") moduli were steady in the strain amplitude range of 0.1-10%. To characterize gelatin matrices formed by the various freezing methods, the ice crystal sizes which were being determined by the scanning electron microscopy (SEM) are affected by the gelatin concentrations. The ice crystal sizes are affected by gelatin concentrations and freezing temperature, while the size distributions of ice crystals depend on the freezing methods. Smaller ice crystals are being formed with PSF rather than under the atmospheric control where the freezing temperature is above -40℃. Thus, the results of this study indicate that the PSF processing at a very low freezing temperature (-50℃) offers a potential advantage over commercial atmospheric freezing points for the formation of small ice crystals.
authors.affiliation: Department of Bioresources and Food Science, Konkuk University, Seoul 143-701, Korea ; Department of Molecular Biotechnology, Konkuk University, Seoul 143-701, Korea.
authors.forename: Byeongsoo
authors.initials: B
authors.lastname: Kim
authors.affiliation: Department of Bioresources and Food Science, Konkuk University, Seoul 143-701, Korea ; Department of Molecular Biotechnology, Konkuk University, Seoul 143-701, Korea.
authors.forename: Hyung Bae
authors.initials: HB
authors.lastname: Gil
authors.affiliation: Department of Bioindustrial Technologies, Konkuk University, Seoul 143-701, Korea.
authors.forename: Sang-Gi
authors.initials: SG
authors.lastname: Min
authors.affiliation: Department of Bioresources and Food Science, Konkuk University, Seoul 143-701, Korea.
authors.forename: Si-Kyung
authors.initials: SK
authors.lastname: Lee
authors.affiliation: Department of Bioresources and Food Science, Konkuk University, Seoul 143-701, Korea.
authors.forename: Mi-Jung
authors.initials: MJ
authors.lastname: Choi
keywords: freeze-drying; freezing rate; gelatin; micro-pore; pressure-shift freezing