| 1. |
- Al-Khafaji, Alia Hussain, et al.
(författare)
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Germination and stress tolerance of oats treated with pulsed electric field at different phases of seedling growth
- 2024
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Ingår i: Bioelectrochemistry. - 1567-5394 .- 1878-562X. ; 158
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Tidskriftsartikel (refereegranskat)abstract
- This study explores the impact of pulsed electric field (PEF) application on oat seedling growth and stress tolerance. PEF treatment (99 monopolar, rectangular pulses lasting 10 µs each, with a frequency of 13 Hz and a nominal electric field strength of 2250 V/cm) was applied at two growth stages: (i) when the seedlings had 0.2 cm roots emerging from the kernel, and (ii) when they had a 0.4 cm shoot emerging from the kernel. Post-treatment, the seedlings were hydroponically grown for 8 days. To induce stress, the hydroponic medium was augmented with PEG (15 %) to induce drought stress and NaCl (150 mM) to induce salinity stress. Results demonstrate that applying PEF improved the growth of the root and shoot of oat seedlings. This effect was more pronounced when applied to more developed seedlings. When PEF was applied during the later stage of germination, seedlings exposed to salinity stress showed enhanced shoot growth compared to the control. Under the studied conditions, the application of PEF had no impact on the growth of seedlings under drought stress.
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| 2. |
- Demir, Eda, et al.
(författare)
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Reversible electroporation caused by pulsed electric field – Opportunities and challenges for the food sector
- 2023
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Ingår i: Trends in Food Science and Technology. - 0924-2244. ; 139
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Forskningsöversikt (refereegranskat)abstract
- Background: The application of Pulsed Electric Field (PEF) to food may result in reversible or irreversible electroporation of cell membranes, depending on whether cell homeostasis is restored after resealing. Restoration of homeostasis upon reversible electroporation implies the recovery of the pre-pulse transmembrane potential and the restoration of cell metabolic functions. Enhanced membrane permeability caused by reversible electroporation would allow impregnation of cells with foreign molecules and/or stress-induced metabolic reactions. The impregnation of cells and the induction of stress in cells could open new opportunities for the application of PEF in the food industry. Scope and approach: Most of the published literature on the application of PEF in food systems focuses on the irreversible process, mainly targeting cold pasteurization or mass/heat transfer enhancement. This review focuses on the application of reversible electroporation to enhance metabolic production of secondary metabolites, to accelerate seed germination and fermentation, and as pre-treatment prior to freezing and drying. Finally, the challenges for industrial application of this technology are discussed. Key findings and conclusions: The application of reversible electroporation as a pre-treatment prior to unit operations in the food industry has the potential to improve the quality of the final product in terms of structure, nutritional value or increased productivity. However, its industrial application faces several challenges, related to difficulties in process optimization, scale-up and equipment design. Therefore, significant efforts are still required to apply reversible electroporation on an industrial scale in the future.
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| 3. |
- Demir, Eda, et al.
(författare)
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Technology Allowing Baby Spinach Leaves to Acquire Freezing Tolerance
- 2018
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Ingår i: Food and Bioprocess Technology. - : Springer Science and Business Media LLC. - 1935-5130 .- 1935-5149. ; 11:4, s. 809-817
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Tidskriftsartikel (refereegranskat)abstract
- This study focuses on improving the freezing tolerance of spinach leaves when applying vacuum impregnation (VI) and pulsed electric fields (PEF) as pre-treatments. Changing the cultivation conditions of the spinach plants was tested for improved freezing tolerance of the harvested leaves. Spinach plants were initially cultivated at 20 °C for 5 weeks and harvested at the beginning of week 6 before the cultivation conditions were changed to 5 °C. After exposing the plants to cold stress, leaves were harvested on day 1, 8, and 20. The leaves from different cultivation temperatures were treated with VI with 30% (w/v) trehalose solution and PEF prior freezing at − 22 °C in a blast freezer. After freezing and thawing, the viability of harvested spinach leaves was 50% for the plants cultivated at 20 °C for 5 weeks. When the cultivation conditions were changed, the viability of the harvested leaves increased to 82% on day 1, 89% on day 8, and without a significant further increase on day 20. During cold cultivation, sucrose accumulated in the leaves, which might have contributed to the increased survival. The influence of impregnating the accumulated sugars instead of changing the cultivation conditions on the survival of the leaves was tested. The viability of the leaves was 75%, which was higher than the survival of the control (50%). The results indicate that it is possible to increase leaf survival after freezing and thawing by applying VI and PEF in combination with either by changing the cultivation conditions of spinach plants or by externally impregnating additional sugars to the harvested leaves.
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| 4. |
- Dymek, Katarzyna, et al.
(författare)
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Effect of pulsed electric field on the germination of barley seeds
- 2012
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Ingår i: LWT - Food Science and Technology. - : Elsevier BV. - 0023-6438. ; 47:1, s. 161-166
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Tidskriftsartikel (refereegranskat)abstract
- This study explores metabolic responses of germinating barley seeds upon the application of pulsed electric fields (PEE). Malting barley seeds were steeped in aerated water for 24 h and PEF-treated at varying voltages (0 (control), 110, 160, 240, 320, 400 and 480 V). The seeds were then allowed to finish germination in saturated air. It is shown that exposure of germinating barley to PEE affects radicle emergence without significantly affecting the seeds gross metabolic activity, as quantified by isothermal calorimetry. An exploration of protein 2-DE profiles of both the embryo and the starchy endosperm showed that, at the studied time scale, no significant changes were found in proteins present at concentrations higher than the detection limit. However, western blotting demonstrated that a-amylase concentration decreases in the PEF-treated seeds. (C) 2011 Elsevier Ltd. All rights reserved.
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| 5. |
- Dymek, Katarzyna, et al.
(författare)
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Influence of Pulsed Electric Field Protocols on the Reversible Permeabilization of Rucola Leaves
- 2014
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Ingår i: Food and Bioprocess Technology. - : Springer Science and Business Media LLC. - 1935-5149 .- 1935-5130. ; 7:3, s. 761-773
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Tidskriftsartikel (refereegranskat)abstract
- Reversible electropermeabilization of plant tissues with heterogeneous structure represents a technological challenge as the response of the different structures within the same specimen to the application of electric field may differ due to different cell sizes, extracellular space configurations, and electrical properties. The influence of five different pulsed electric field protocols with different pulse polarity, number of pulses (25, 50, 75, 100, 250, and 500), and intervals between pulses (no intervals and 1- and 2-ms intervals) on the reversible permeabilization of rucola (Eruca sativa) leaves was investigated. The electric field intensity was 600 V/cm. Electrical resistance of the bulk tissue was measured before and after electroporation, and propidium iodide was used to analyze the electroporation at the surface of the leaf. Leaf viability was assessed from survival in storage, and cell viability was investigated with fluorescein diacetate. Results indicate that the viability of the leaves could not be predicted by measurements of electrical resistance or permeabilization levels of the leaf surface. Higher survival rate was demonstrated when applying bipolar pulses compared with monopolar pulses, but the latter proved to be more effective than bipolar pulses for permeabilizing the surface of the leaves. Longer intervals between bipolar pulses resulted in increased viability preservation, while the number of electroporated cells on the leaf surface was comparable for all tested protocols.
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| 6. |
- Dymek, Katarzyna, et al.
(författare)
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Influence of vacuum impregnation and pulsed electric field on the freezing temperature and ice propagation rates of spinach leaves
- 2015
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Ingår i: LWT - Food Science and Technology. - : Elsevier BV. - 0023-6438. ; 64:1, s. 497-502
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Tidskriftsartikel (refereegranskat)abstract
- Efforts are currently directed towards improving the quality of sensitive tissues of fruits and vegetables after freezing and thawing. One of the methods under investigation is the combination of vacuum impregnation (VI) with cryoprotectants and pulsed electric field (PEF), applied to the plant tissue prior exposure to freezing. The influence of these processes on the freezing temperature and ice propagation rate of spinach baby leaves are here studied. Leaves impregnated with trehalose, sucrose, glucose and mannitol exhibited significantly lower ice propagation rate and higher freezing temperatures in comparison to non-treated controls. Leaves subjected to PEF also showed increased freezing temperatures compared to the non-treated leaves; however the ice propagation rate was not influenced by PEF for the cryoprotectants used in the study, except for leaves impregnated with trehalose, where it was significantly increased and water, where it was significantly decreased. The combination of VI and PEF resulted in comparable freezing temperatures and ice propagation rates as the leaves subjected only to VI. (C) 2015 Elsevier Ltd. All rights reserved.
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| 7. |
- Dymek, Katarzyna, et al.
(författare)
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Modeling electroporation of the non-treated and vacuum impregnated heterogeneous tissue of spinach leaves
- 2015
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Ingår i: Innovative Food Science & Emerging Technologies. - : Elsevier BV. - 1466-8564. ; 29, s. 55-64
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Tidskriftsartikel (refereegranskat)abstract
- Uniform electroporation of the heterogeneous structure of spinach leaf cross section is a technological challenge that is addressed in this investigation. Three dimensional models were created with cells arranged in specific tissue types, considering a leaf with its air fraction and a leaf where the air fraction was replaced by a solution of known properties using vacuum impregnation. The models were validated before electroporation, in the frequency domain, where alternating voltage and current signal at frequencies from 20 Hz to I MHz were used to measure conductivity of the tissue. They were also validated through measurements of current during electroporation when a single 250 mu s rectangular pulse with amplitudes ranging from 50 to 500 V was applied. Model validations show that both the frequency dependent conductivity and electroporation are well predicted. The importance of the wax layer and stomata in the model is thoroughly discussed. Industrial relevance: Our aim was to investigate electroporation of the spinach leaf by developing a model which would enable us to meet the technological challenge of achieving uniform electroporation in a highly heterogeneous structure in the context of a process aimed at improving freezing stability of plant foods. Pulsed electric field treatment may be used to introduce the cryoprotectant molecules into the cells, and hence improve the structure and properties of frozen food plants. (C) 2014 Elsevier Ltd. All rights reserved.
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| 8. |
- Escobar, Mayra Paredes, et al.
(författare)
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Effect of long-term storage and blanching pre-treatments on the osmotic dehydration kinetics of carrots (Daucus carota L. cv. Nerac)
- 2007
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774. ; 81:2, s. 313-317
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Tidskriftsartikel (refereegranskat)abstract
- The effect of postharvest long-term storage and pre-treatments on the mass transfer rates during osmotic dehydration of carrots was investigated. Four blanching times were used and the carrots were sampled during 12 weeks of storage. Cell vitality was measured by isothermal calorimetry on cores taken from blanched slices. During the storage period, effective diffusion coefficients for water and sucrose transport were determined in the non-blanched and blanched carrot parenchyma. For every time point during long-term storage, the effective diffusion coefficients increased with an increase in blanching time which caused the death of cells in the tissue. This increase showed to be dependent on the storage time of the carrots. It was inferred that structural changes in the cell wall of the carrot parenchyma during storage substantially decreases the effect of blanching on the effective diffusion coefficients. (c) 2006 Elsevier Ltd. All rights reserved.
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| 9. |
- Galindo, Federico Gómez
(författare)
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Physiological and biochemical aspects of vegetable processing. A case study on carrots
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of the present study was to enhance our understanding of vegetables as living organisms, interacting dynamically with the environment, and to explore the possible influence of metabolic changes on subsequent processing operations. Growing conditions, harvesting and handling in the packing house and storage conditions are key events leading to a defined “physiological status” of the vegetable that is going to be consumed as a fresh product or a processed product. Different events during the lifetime of vegetables are reviewed and analysed from the point of view of the physiological transformations taking place in each of them. Aspects of plant stress physiology were of particular interest. The physiological response to low-temperature stress, known as cold acclimation, was studied using carrots. The presence and accumulation of an antifreeze protein (AFP) in the carrot cell wall was used as a biological marker for the study of the induction of cold acclimation in carrot taproots. It was demonstrated that AFP gene expression was rapidly upregulated in response to low-temperature exposure. Furthermore, the induction of this gene was clearly affected by the temperature at which the taproots had been grown. The results also indicated that the development of cold acclimation in stored carrots, shown by the accumulation of AFP, was consistent with a high storage potential of the harvested taproots. The influence of cold acclimation on the mechanical strength of the harvested roots was studied. Tissue rigidity increased after 12 weeks of storage, at which time a higher accumulation of AFP was found. It was suggested that oxidative cross-linking between extensin proteins in the cell wall may be part of the mechanism behind the storage-induced firmness of carrots. The potential benefits of cold acclimation for the enhancement of quality upon freezing in the food industry are reviewed. The damaging action of a preceding blanching operation is discussed and the alternative of using mild blanching to minimize tissue damage was investigated. Isothermal calorimetry was used as a technique to quantify cell damage due to mild blanching of carrot slices. The results suggest that the mild blanching treatment, intended to inactivate the enzymes responsible for the development of off-flavours, may be accompanied by the inactivation of cell metabolism and hence, cell damage to about 70% of the cells in the carrot slices. Radiation in the far-infrared region was tested as a technological alternative to minimize cell damage. Radiation in the far-infrared region damaged cells to a depth of only 0.5 mm in the carrot slices, preserving cell integrity and most of the texture characteristics of the raw tissue. Basic scientific studies on the changes in vegetable cellular systems before harvest and after harvest and processing are necessary to provide the knowledge needed by food engineers on vegetables as biological materials. The use of this knowledge is of critical importance as a tool for process optimization in the food industry. The present study represents a contribution to this knowledge.
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| 10. |
- Galindo, Federico Gómez, et al.
(författare)
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Pulsed electric fields in combination with vacuum impregnation for improving freezing tolerance of vegetables
- 2017
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Ingår i: Handbook of Electroporation. - Cham : Springer International Publishing. - 9783319328850 - 9783319328867 ; 3, s. 2135-2151
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Bokkapitel (refereegranskat)abstract
- Freezing is a widely used method of preserving food products. Efforts are currently being directed towards improving the quality of sensitive tissues of plant foods such as leaves, after freezing and thawing. One of the methods under investigation is the combination of vacuum impregnation (VI) with cryoprotectants and the application of a pulsed electric field (PEF) to the plant tissue prior to freezing. In this chapter were identify mechanisms for the efficient introduction of a cryoprotectant molecule into the heterogeneous structure of leaf tissue and improve our understanding of the consequences of the introduction of this foreign molecule into the tissue regarding cell metabolism, freezing point, and ice propagation rate. To obtain precise information on the electroporation of internally located cells, a three-dimensional numerical model of the cross section of a leaf was developed. Validation of the models showed the importance of the wax layer and stomata for the successful electroporation of all cells in the tissue. VI, and the subsequent application of PEF, increased the metabolic activity of the tissue. The increase in metabolic activity after VI was accompanied by the accumulation of trehalose-6-phosphate in the cells. Leaves impregnated with trehalose, sucrose, glucose, and mannitol exhibited significantly lower ice propagation rates and higher freezing temperatures than untreated controls. Leaves subjected to PEF also showed higher freezing temperatures than untreated leaves; however, the ice propagation rate was not influenced by PEF.
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