• Food Science of Animal Resources
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• v.34 no.1
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• pp.33-39
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• 2014

This study investigates the effects of the gelatin concentration (10-40%, w/v), freezing temperatures (from $-20^{\circ}C$ to $-50^{\circ}C$) 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 $-0.2^{\circ}C$ (10% gelatin) to $-6.7^{\circ}C$ (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 $-40^{\circ}C$. Thus, the results of this study indicate that the PSF processing at a very low freezing temperature ($-50^{\circ}C$) offers a potential advantage over commercial atmospheric freezing points for the formation of small ice crystals.

• Food Science of Animal Resources
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• v.26 no.4
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• pp.464-470
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• 2006

This study was carried out to investigate the effect of various high pressure freezing treatments on the physical properties of pork To compare the effect of freezing on meat quality, atmospheric freezing (AF), pressure and freezing (PF), pressure shift freezing (USF) and pressure assisted freezing (PAF) were conducted at pressure of 100 MPa. Water binding properties, shear force and colour were measured as physical properties of pork PAF showed shorter phase transition time than PSF. Although significant increase (p<0.05) in water binding properties was found only at PAF, meat frozen under hydrostatic pressure environment showed improved water binding properties. However, all high pressure freezing treatment caused significantly increased shear force (p<0.05), especially at PF treatment. In color, all high pressure freezing treatments showed significantly higher color parameters (p<0.05) than AF, whilst no significant differences among high pressure freezing treatments were found (p>0.05). Therefore the result indicated that applied hydrostatic pressure improved functional properties of pork with increasing freezing rate and PAF had more potential benefit than PSF at mild pressure range.

• Food Science of Animal Resources
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• v.29 no.6
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• pp.736-742
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• 2009

This study was conducted to investigate the effect of various high pressure freezing and thawing treatments on the physical properties of pork. To compare the effects of the freezing and thawing process on meat quality, atmospheric freezing followed by running water thawing (AFRT), pressure shift freezing followed by running water thawing (SFRT), and pressure shift freezing and pressure assisted thawing (SFAT) were conducted at pressure of 250 MPa and cooling temperature of $-22^{\circ}C$. SAFT and SFRT showed a shorter phase transition time and total thawing time than AFRT. The pH value of treated samples increased significantly (p<0.05) compared to unfrozen meat. In addition, SFAT and SFRT showed a higher pHvalue than AFRT. Although the water holding capacity was significantly decreased (p<0.05) for SFAT and SFRT, SFRT reduced drip loss. In regards to color, SFAT and SFRT resulted in a significant increase in color parameters (p<0.05) relative to AFRT, while SFAT produced a higher L*-value. High pressure treatment significantly increased shear force (p<0.05) compared to AFRT, and, where SFRT showed the highest shear force. Therefore, these combined results indicated that the hydrostatic pressure treatment improved the functional properties of pork and increased the freezing and thawing rate.

• Food Science of Animal Resources
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• v.36 no.3
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• pp.335-342
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• 2016

The object in this study is to investigate the effects of high pressure and freezing processes on the curdling of skim milk depending on the presence of transglutaminase (TGase) and glucono-δ-lactone (GdL). Skim milk was treated with atmospheric freezing (AF), high pressure (HP), pressure-shift freezing (PSF) and high pressure sub-zero temperature (HPST) processing conditions. After freezing and pressure processing, these processed milk samples were treated with curdling agents, such as TGase and GdL. Pressurized samples (HP, PSF and HPST) had lower lightness than that of the control. In particular, PSF had the lowest lightness (p<0.05). Likewise, the PSF proteins were the most insoluble regardless of whether they were activated by TGase and GdL, indicating the highest rate of protein aggregation (p<0.05). Furthermore, the TGase/GdL reaction resulted in thick bands corresponding to masses larger than 69 kDa, indicating curdling. Casein bands were the weakest in PSF-treated milk, revealing that casein was prone to protein aggregation. PSF also had the highest G' value among all treatments after activation by TGase, implying that PSF formed the hardest curd. However, adding GdL decreased the G' values of the samples except HPST-treated samples. Synthetically, the PSF process was advantageous for curdling of skim milk.

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
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• 2005.10a
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• pp.136-141
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• 2005

In this research, PSF and PBF indicated beneficial influence on water binding ability of meat comparing to conventional freezing methods. High pressure in freezing process resulted some changes inhysical characteristics of pork: increment each color value, shear force and pH in PSF, PAF and PBF.