Thermal characterization and ice crystal analysis in pressure shift freezing of different muscle (shrimp and porcine liver) versus conventional freezing method

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.

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Ice-crystal formation in gelatin gel during pressure shift versus conventional freezing

Journal of Food Engineering ◽

10.1016/j.jfoodeng.2004.02.035 ◽

2005 ◽

Vol 66 (1) ◽

pp. 69-76 ◽

Cited By ~ 55

Author(s):

Songming Zhu ◽

Hosahalli S. Ramaswamy ◽

Alain Le Bail

Keyword(s):

Crystal Formation ◽

Ice Crystal ◽

Pressure Shift ◽

Ice Crystal Formation ◽

Conventional Freezing

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Cryosectioning plant roots prepared by high-pressure freezing

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100127748 ◽

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.

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