Effects of High-Pressure Low-Temperature Freezing&Thawing Process on Potato Qualities

2012 ◽  
Vol 554-556 ◽  
pp. 1521-1525
Author(s):  
Zhi Yi Li ◽  
Shu Hua Chen ◽  
Feng Xia Liu ◽  
Wei Wei ◽  
Zhi Jun Liu
Keyword(s):  
High Pressure ◽  
Pressure Effects ◽  
Freezing Process ◽  
Ice Crystal ◽  
High Pressure Freezing ◽  
Pressure Shift ◽  
Combination Effects ◽  
Model Object ◽  
Thawing Process ◽  
Pressure Shift Freezing

The research about the high pressure technology to preserve foodstuff has been studied for a longer time, but there were few of papers about the research of the combination effects of high-pressure-freezing&thawing process on food qualities. To examine the combination effects of high-pressure-freezing&thawing process on food qualities, potato was chosen as model object. The experiments were conducted with pressure-shift-freezing processes at 0.1, 100~200MPa, and pressure-assisted-thawing processes at 0.1, 200MPa. Texture analysis was as the key index to evaluate the combination effects of high-pressure-freezing&thawing process on food qualities by Texture Analyzer. At the same time the frozen samples treated by pressure-shift-freezing process were histologically analyzed using the isothermal freezing substitution technique to contrast the pressure effects on the size and shape of ice crystal. The sizes and locations of ice crystals in samples as a result of pressure-shift-freezing were compared to those obtained by atmospheric freezing. The results showed that the combination of pressure-shift-freezing and pressure-assisted-thawing process made less change on the cell wall.

scholarly journals Generalized enthalpy model of a high-pressure shift freezing process

2012 ◽  
Vol 468 (2145) ◽  
pp. 2744-2766 ◽  
Author(s):  
Nadia A. S. Smith ◽  
Stephen S. L. Peppin ◽  
Ángel M. Ramos
Keyword(s):  
High Pressure ◽  
Stokes Equations ◽  
Freezing Point ◽  
Food Samples ◽  
Navier Stokes ◽  
Freezing Process ◽  
Frozen Foods ◽  
Navier Stokes Equations ◽  
Pressure Shift ◽  
Pressure Shift Freezing

High-pressure freezing processes are a novel emerging technology in food processing, offering significant improvements to the quality of frozen foods. To be able to simulate plateau times and thermal history under different conditions, in this work, we present a generalized enthalpy model of the high-pressure shift freezing process. The model includes the effects of pressure on conservation of enthalpy and incorporates the freezing point depression of non-dilute food samples. In addition, the significant heat-transfer effects of convection in the pressurizing medium are accounted for by solving the two-dimensional Navier–Stokes equations. We run the model for several numerical tests where the food sample is agar gel, and find good agreement with experimental data from the literature.

Effect of High Pressure Shift Freezing Process on Microbial Inactivation in Dairy Model Food System

2008 ◽  
Vol 4 (5) ◽  
Author(s):  
Mi Jung Choi ◽  
Sang Gi Min ◽  
Geun Pyo Hong
Keyword(s):  
High Pressure ◽  
Food System ◽  
Microbial Inactivation ◽  
Holding Time ◽  
Freezing Process ◽  
Pressure Shift ◽  
E Coli ◽  
Uht Milk ◽  
Log Reduction ◽  
Pressure Shift Freezing

This study was carried out to investigate the microbial inactivation in dairy model system by high pressure shift freezing (HPSF). The UHT milk and broths were inoculated with Escherichia coli ATCC 25922, Staphylococcus aureus KCCM 11335 and Listeria monocytogenes HTCC 19115, respectively. The samples were pressurized to 200 MPa under different holding time at -18ºC. Inactivation effects of both E. coli ATCC 25922 and L. monocytogenes HTCC 19115 were significantly shown by the increment of pressure holding time (p<0.05) for not only in broth, but also UHT milk. The highest value of log reduction in NB media was observed as 6.1 after HPSF. However, inactivation effects of S. aureus KCCM 11335 were not significantly shown in tryptic soy broth (TSB) and UHT milk.

High-pressure freezing of cells in suspension for low-voltage scanning electron microscopy (LVSEM)

1991 ◽  
Vol 49 ◽  
pp. 64-65
Author(s):  
Marek Malecki ◽  
James Pawley ◽  
Hans Ris
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
Low Voltage ◽  
Culture Media ◽  
Cell Structure ◽  
Freeze Substitution ◽  
Ice Crystal ◽  
High Pressure Freezing ◽  
Cell Culture Media ◽  
Voltage Scanning

The ultrastructure of cells suspended in physiological fluids or cell culture media can only be studied if the living processes are stopped while the cells remain in suspension. Attachment of living cells to carrier surfaces to facilitate further processing for electron microscopy produces a rapid reorganization of cell structure eradicating most traces of the structures present when the cells were in suspension. The structure of cells in suspension can be immobilized by either chemical fixation or, much faster, by rapid freezing (cryo-immobilization). The fixation speed is particularly important in studies of cell surface reorganization over time. High pressure freezing provides conditions where specimens up to 500μm thick can be frozen in milliseconds without ice crystal damage. This volume is sufficient for cells to remain in suspension until frozen. However, special procedures are needed to assure that the unattached cells are not lost during subsequent processing for LVSEM or HVEM using freeze-substitution or freeze drying. We recently developed such a procedure.

Cryosectioning plant roots prepared by high-pressure freezing

1987 ◽  
Vol 45 ◽  
pp. 662-663
Author(s):  
R.E. Crang ◽  
M. Mueller ◽  
K. Zierold
Keyword(s):  
High Pressure ◽  
Cell Walls ◽  
Plant Tissues ◽  
Ice Crystal ◽  
High Pressure Freezing ◽  
Vitreous State ◽  
Radial Depth ◽  
Irregular Topography ◽  
Considerable Depth ◽  
Conventional Freezing

Obtaining frozen-hydrated sections of plant tissues for electron microscopy and microanalysis has been considered difficult, if not impossible, due primarily to the considerable depth of effective freezing in the tissues which would be required. The greatest depth of vitreous freezing is generally considered to be only 15-20 μm in animal specimens. Plant cells are often much larger in diameter and, if several cells are required to be intact, ice crystal damage can be expected to be so severe as to prevent successful cryoultramicrotomy. The very nature of cell walls, intercellular air spaces, irregular topography, and large vacuoles often make it impractical to use immersion, metal-mirror, or jet freezing techniques for botanical material.However, it has been proposed that high-pressure freezing (HPF) may offer an alternative to the more conventional freezing techniques, inasmuch as non-cryoprotected specimens may be frozen in a vitreous, or near-vitreous state, to a radial depth of at least 0.5 mm.

High-pressure freezing and freeze substitution of plant tissue

1992 ◽  
Vol 50 (1) ◽  
pp. 748-749
Author(s):  
William P. Sharp ◽  
Robert W. Roberson
Keyword(s):  
High Pressure ◽  
Cell Structure ◽  
Leaf Tissue ◽  
Freeze Substitution ◽  
Crystal Formation ◽  
Ice Crystal ◽  
High Pressure Freezing ◽  
Cell Components ◽  
Cold Metal ◽  
Brome Grass

The aim of ultrastructural investigation is to analyze cell architecture and relate a functional role(s) to cell components. It is known that aqueous chemical fixation requires seconds to minutes to penetrate and stabilize cell structure which may result in structural artifacts. The use of ultralow temperatures to fix and prepare specimens, however, leads to a much improved preservation of the cell’s living state. A critical limitation of conventional cryofixation methods (i.e., propane-jet freezing, cold-metal slamming, plunge-freezing) is that only a 10 to 40 μm thick surface layer of cells can be frozen without distorting ice crystal formation. This problem can be allayed by freezing samples under about 2100 bar of hydrostatic pressure which suppresses the formation of ice nuclei and their rate of growth. Thus, 0.6 mm thick samples with a total volume of 1 mm3 can be frozen without ice crystal damage. The purpose of this study is to describe the cellular details and identify potential artifacts in root tissue of barley (Hordeum vulgari L.) and leaf tissue of brome grass (Bromus mollis L.) fixed and prepared by high-pressure freezing (HPF) and freeze substitution (FS) techniques.

Preservation of Microstructure in Peach and Mango during High-pressure-shift Freezing

2000 ◽  
Vol 65 (3) ◽  
pp. 466-470 ◽  
Author(s):  
L. Otero ◽  
M. Martino ◽  
N. Zaritzky ◽  
M. Solas ◽  
P.D. Sanz
Keyword(s):  
High Pressure ◽  
Pressure Shift ◽  
Pressure Shift Freezing

Cryo-SEM and TEM of High Pressure Frozen Cells - Some Technical Contributions

2001 ◽  
Vol 7 (S2) ◽  
pp. 728-729
Author(s):  
Paul Walther
Keyword(s):  
High Pressure ◽  
Physiological State ◽  
Electron Microscopic Observation ◽  
Freeze Substitution ◽  
Chemical Fixation ◽  
Ice Crystal ◽  
High Pressure Freezing ◽  
Electron Microscopic ◽  
Biological Specimen ◽  
Freeze Fracturing

Imaging of fast frozen samples is the most direct approach for electron microscopy of biological specimen in a defined physiological state. It prevents chemical fixation and drying artifacts. High pressure freezing allows for ice-crystal-free cryo-fixation of tissue pieces up to a thickness of 200 urn and a diameter of 2 mm without prefixation. Such a frozen disc, however, is not directly amenable to electron microscopic observation: The structures of interest have to be made amenable to the electron beam, and the structures of interest must produce enough contrast to be recognized in the electron microscope. This can be achieved by freeze fracturing, cryo-sectioning or freeze substitution.The figures show high pressure frozen bakers yeast saccharomyces cerevisiae in the cryo-SEM (Figures 1 and 2) and after freeze substitution in the TEM (Figure 3). For high pressure freezing either a Bal-Tec HPM 010 (Princ. of Liechtenstein; Figures 1 and 2), or a Wohlwend HPF (Wohlwend GmbH, Sennwald, Switzerland; Figure 3) were used.

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