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PFG-NMR study for evaluating freezing damage to onion tissue
Hiroko Ando1, Mika Fukuoka, Osato Miyawaki
1Department of Biological and Environmental Engineering, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
Abstract:
We assessed the damage to onion tissue due to freeze-thawing as the water permeability determined by using PFG-NMR and light microscopy. The water diffusion in fresh onion tissue was restricted due to cellular barriers, and the estimated water permeability was 6.99 x 10(-6)m/s. The water diffusion became considerably less restricted after freeze-thawing; the convergent value for the restricted diffusion coefficient increased and the water permeability significantly increased to 2.85 x 10(-5) m/s. While NMR could detect a distinct change in the diffusion behavior of water molecules in freeze-thawed tissue, light microscopy revealed no significant tissue damage. These results suggest that freeze-thawing damaged the vegetable tissues primarily through destruction of the cell membrane rather than the cell wall.
Insights
Freeze-thawing significantly increases water permeability in onion tissue by damaging cell membranes, as detected by pulsed-field gradient nuclear magnetic resonance (PFG-NMR), even when light microscopy shows no visible tissue damage.
Area of Science:
- Plant physiology
- Biophysics
- Food science
Background:
- Freeze-thawing is a common process affecting vegetable tissues.
- Understanding cellular damage mechanisms is crucial for food preservation.
- Water transport properties are key indicators of cellular integrity.
Purpose of the Study:
- To quantify the effect of freeze-thawing on water permeability in onion tissue.
- To investigate the cellular structures affected by freeze-thaw cycles.
- To compare the sensitivity of PFG-NMR and light microscopy in detecting freeze-thaw damage.
Main Methods:
- Water permeability was measured using pulsed-field gradient nuclear magnetic resonance (PFG-NMR).
- Light microscopy was employed to visually assess tissue integrity.
- Water diffusion coefficients and permeability were calculated for fresh and freeze-thawed onion tissues.
Main Results:
- Water diffusion in fresh onion tissue was restricted, with a permeability of 6.99 x 10(-6) m/s.
- Freeze-thawing significantly increased water permeability to 2.85 x 10(-5) m/s.
- PFG-NMR detected altered water diffusion, while light microscopy showed no significant structural damage.
Conclusions:
- Freeze-thawing primarily damages vegetable tissues by disrupting cell membranes, not cell walls.
- PFG-NMR is a sensitive technique for detecting sub-visual cellular damage caused by freeze-thawing.
- Cell membrane integrity is critical for regulating water transport in plant tissues.
