Electric Field Treatment Research Articles

Impact of pulsed electric field treated milk on quality of paneer and khoa.

The present work was undertaken to investigate the feasibility of pre-treatment of raw milk with Pulse Electric Field (PEF) treatment before its entry into the processing chain. A custom-designed and fabricated PEF applicator was used for the non-thermal treatment protocol. Raw milk was treated under three treatment protocols, viz., conventionally heat treatment (CHT), PEF treated milk subjected to conventional heat treatment (PT-CHT) and PEF treatment (PT). For the PT protocol, milk was subjected to high voltage (55 kV) square wave of pulse width 900 µs, for 100 s at a frequency of 90 Hz. The treated milk was then converted to two popular products, namely and paneer and khoa, which were evaluated for its physico-chemical, microbiological, sensory quality and shelf stability. Since khoa is a heat desiccated product, it was evaluated only against PT-CHT and CHT treatments. It was observed that PT treatment resulted in paneer with softer body with higher whiteness index, compared to other experimental samples. The PT treatment did not affect the product acceptability and the product had a shelf stability of 12 days under refrigeration, as against 16 days for CHT and PT-CHT treatment. The treatment protocols for milk did not significantly affect the quality and shelf life of khoa. Thus, there is wide future scope to used pulsed electric fields treatment synergistically with conventional heat treatment for inactivation of microorganisms, with better retention of nutritional and physical properties of product which has potential to save considerable amount of energy and time during processing of product.

Anisotropic silk nanofiber layers as regulators of angiogenesis for optimized bone regeneration.

Osteogenesis-angiogenesis coupling processes play a crucial role in bone regeneration. Here, electric field induced aligned nanofiber layers with tunable thickness were coated on the surface of pore walls inside the deferoxamine (DFO)-laden silk fibroin (SF) and hydroxyapatite (HA) composite scaffolds to regulate the release of DFO to control vascularization dynamically. Longer electric field treatments resulted in gradually thickening layers to reduce the release rate of DFO where the released amount of DFO decreased gradually from 84% to 63% after 28 days. Besides the osteogenic capacity of HA, the changeable release of DFO brought different angiogenic behaviors in bone regeneration process, which provided a desirable niche with osteogenic and angiogenic cues. Anisotropic cues were introduced to facilitate cell migration inside the scaffolds. Changeable cytokine secretion from endothelial cells cultured in the different scaffolds revealed the regulation of cell responses related to vascularization in vitro. Peak expression of angiogenic factors appeared at days 7, 21 and 35 for endothelial cells cultured in the scaffolds with different silk nanofier layers, suggesting the dynamical regulation of angiogenesis. Although all of the scaffolds had the same silk and HA composition, in vitro cell studies indicated different osteogenic capacities for the scaffolds, suggesting that the regulation of DFO release also influenced osteogenesis outcomes in vitro. In vivo, the best bone regeneration occurred in defects treated with the composite scaffolds that exhibited the best osteogenic capacity in vitro. Using a rat bone defect model, healing was achieved within 12 weeks, superior to those treated with previous SF-HA composite matrices. Controlling angiogenic properties of bone biomaterials dynamically is an effective strategy to improve bone regeneration capacity.

Total phenolic, isothiocyanate and radicle elongation determination of mung bean sprout during germination affected by different variables of pulsed electric field treatment

Mung bean germination started with moisture uptake, biochemical modification, interconversion and biosynthesis of metabolites. Mung bean sprout was commonly used a fresh salad vegetable with available amino acids, dietary fiber, minerals, vitamins and phytonutrients. Pulsed electric field (PEF) was a prominent technology as a green approach for improvement of seed germination. This research evaluated some technical parameters of PEF such as pulse electric field strength (300-1500 kV/cm), pulse number (50-250) and pulse width (1.0-3.0 µs) at a stable frequency 1 Hz in ambient temperature on the total phenolic, isothiocyanate and radicle elongation of mung bean sprout. Results showed that pulse electric field strength and pulse number significantly increased isothiocyanate and total phenolic content while retardation of root length extension. Meanwhile pulse width showed a negative impact on total phenolic, isothiocyanate while extending root length extension. PEF should be conducted at pulse electric field strength (1200 kV/cm), pulse number (150), pulse width (1.5 µs) to retain the highest isothiocyanate (33.96±0.35 nmol/sprout) and total phenolic (221.30±1.46 mg GAE/100 g) while keeping a fair radicle elongation (8.39±0.17 mm). PEF treatment would be a promising non-lethal technology feasible for mung bean seed sprouting improvement.

Assessment of non-pressurized electro dewatering of waste activated sludge with graphite electrodes

Changes of physical and chemical characteristics of sludge were investigated with respect to the pH, process time, and applied voltage by means of the electric field treatments. A model reactor with the desired speed was used to generate an electric field to separate water from the sludge without applying pressure. All electrodes mounted on the reactor were produced from graphite. Two different distances between anode and cathode (2.3 cm and 4.3 cm) were used to examine the effects on dewatering capacity of sludge. Differentiations of dependent variables inferred from the experimental processes were also surveyed by Box-Behnken experimental design. The water in the sludge was separated effectively when the samples were exposed to an electric field. The total solid increased from 1.07% to 6.60% at pH 6.5 when sludge was exposed to 25 V for 60 min. Furthermore, the optimum distance between electrodes was 2.3 cm for dewatering of sludge samples, where the capillary suction time of influent sludge was observed to decrease by approximately 85.5% at raw sludge pH. Similarly, the viscosity parameters decreased by approximately 99%. There was an increase in the soluble chemical oxygen demand, PO4-P, and NH4-N concentrations of water discharged from the model reactor.

Regulatory effects of bio-intensity electric field on transformation of human skin fibroblasts

Regulatory effects of bio-intensity electric field on transformation of human skin fibroblasts

Evaluation of the structure-activity relationship between allergenicity and spatial conformation of ovalbumin treated by pulsed electric field

The aim of the present study was to investigate the effect of pulsed electric field (PEF) treatment on ovalbumin (OVA) induced allergens and reveal potential allergy regulatory mechanisms. At 10 kV/cm, OVA-induced allergic symptoms were significantly reduced, and the capacity of OVA to bind with specific IgG1 and IgE was reduced by 10.32% and 3.61%, respectively. Furthermore, the degranulation of RBL-2H3 cells and allergen activity were also reduced by 4.63% and 22.15%, respectively. Interestingly, the α-helix content was reduced by 5.81% and the fluorescence intensity was increased by 6.90% with PEF treatment. At 10 kV/cm, water contact angle and surface hydrophobicity increased by 8.40% and 0.18%, respectively, indicating that PEF treatment increased the exposure of hydrophobic amino acid residues. PEF treatment alters the hydrogen bonding and hydrophobic interactions in the protein, which masks the binding sites of sensitized epitopes, and consequently reduces allergies.

Повышение эффективности снятия покровной ткани с плодов томата импульсным электрическим полем

Electrophysical technologies are a global trend of sustainable agriculture and food industry. Peeling is an energy-intensive procedure of fruit and vegetable processing. The research featured the effect of pulsed electric field (PEF) treatment on tomato peeling effectiveness. The assessment included such factors as specific effort, energy costs, and product losses in comparison with thermal and electrophysical methods.
 Tomatoes of Aurora variety underwent a PEF treatment at 1 kV/cm. The expended specific energy was 1, 5, and 10 kJ/kg. The tomatoes were visually evaluated with optical microscopy before and after processing. The peeling effectiveness and mass loss were measured with a texture analyzer and digital scales.
 The PEF treatment decreased the specific force of mechanical peel removal by 10% (P < 0.05). The mass loss decreased by 4% (P < 0.05) at 1 kJ/kg. The PEF method resulted in cell electroporation, which activated the internal mass transfer of moisture from the endocarp region between the mesocarp and the integumentary tissue. The hydrostatic pressure produced a layer of liquid, which facilitated the peeling.
 In comparison with thermal treatment (blanching), ohmic heating, and ultrasonic processing, the PEF technology had the lowest production losses and energy costs. The research proves the prospects of the PEF treatment in commercial tomato processing.

Application of Pulsed Electric Field as a Pre-Treatment for Subcritical Water Extraction of Quercetin from Onion Skin.

Pulsed electric field (PEF) treatment promotes the electroporation of biological membranes, and if included as a pre-treatment, could improve the extraction of certain constituents therefrom. The aim of this study was to determine the optimal extraction conditions for extracting the flavonoid quercetin from dried onion skin and to establish whether the yield could be enhanced by combining PEF pre-treatment with an eco-friendly extraction method that uses subcritical water extraction (SWE). Samples of onion skin were treated with PEF under conditions of varying electric field strength (0.5–2.5 kV/cm) and duration (5–120 s). SWE was then performed with an extraction time of 15 min and at temperatures ranging from 105 °C to 185 °C. Among the conditions tested, the yield of total quercetin was the highest after pretreatment with PEF at 2.5 kV/cm for 15 s, followed by SWE at 145 °C for 15 min (yield 19.25 ± 0.77 mg/g dried onion skin, mean ± standard deviation). Pretreatment with PEF improved the yield of total quercetin extracted by 33.22% compared with the PEF-untreated samples. These findings demonstrate that pretreatment of onion skin with PEF has the potential to improve flavonoid extraction.

Influence of moderate electric field on sodium caseinate structure and its techno-functionality

This study aimed to evaluate the effect of moderate electric field (MEF) treatment, as a non-thermal technology, on the structure and techno-functionality of sodium caseinate. Colloidal dispersions of caseinate were subjected to different MEF processing conditions (2.56 V cm −1 for 1 and 2 h, 38.46 V cm −1 for 5 and 20 s) and their structural, physical, emulsifying and film-forming characteristics were assessed. The Fourier transform infrared (FTIR) analysis of the caseinate showed higher β-structures and a reduction in random coil conformation after MEF. The MEF-treated dispersions exhibited smaller particle size and developed emulsions with higher physical stability. The process increased the tensile strength (by 6.52–27.37%) and stretchability (by 12.17–54.30%) of caseinate film. A higher glass transition temperature in MEF-processed caseinate films was confirmed by modulated differential scanning calorimetry (MDSC) profiles. The scanning electron microscope (SEM) images showed a more uniform microstructure in treated caseinate films. The results suggest that MEF may be efficiently applied for mild modification of the structure of caseinate resulting in its property improvement. • Moderate electric field (MEF) treatment was applied to sodium caseinate. • MEF presented significant actions on the caseinate structure. • Non-thermal effects of MEF enhanced caseinate techno-functionality. • Treated caseinate yielded emulsions with higher stability and smaller droplet size. • MEF-subjected caseinate films possessed higher mechanical strength and stretchability.

Pulsed Electric Field Treatment of Raw Milk and Its Effect on Protein-Free Amino Acids Transition

As a nonthermal microbial inactivation technology, pulsed electric field (PEF) treatment technology shows potentials in liquid food sterilization and other biological applications. The purpose of this study is to investigate the effect of PEF treatment on sterilization, the physical and the chemical properties of raw milk. Fresh raw milk samples were subject to PEF process with electric field strength ranged from 15 to 35 kV/cm for 1.25–5 ms in this study. The sterile rate and the shelf-life were evaluated and compared for PEF-treated, pasteurized, and untreated raw milk samples. It was demonstrated that similar inactivation effect was achieved as compared with pasteurization when raw milk was PEF-treated for 5 ms using 35-kV/cm field strength. The concentration of protein and free amino acids (FAA) was also measured and the results indicated that the PEF process promoted the protein-FAA transition as the concentration of FAA in the raw milk sample increased by as much as 14%. It is also shown that the input energy density of PEF treatment can be the deciding factor which affects both inactivation of microorganisms and the transformation of composition in the liquid food.

Improving postharvest quality of tomato with the application of electric field treatment

Improving postharvest quality of tomato with the application of electric field treatment

Scale inhibition performance of an electric field on a heat transfer surface: Experiments and molecular dynamics simulation

Because of the electric field method has the characteristics of energy saving, environmental protection and high efficiency, it is the focus of research in this field at present. In this study, a molecular dynamics method was used to simulate the effect of an electric field on the interaction of Ca2+ and CO32− in calcium carbonate solution with the surface of calcite crystals (1, -1, 0), and through experiments, the performance of an electric field with an intensity of 1000–1400 V/m (step 100 V/m) to inhibit calcium carbonate deposition on the heat transfer surface was studied. The simulation results showed that the binding energy of Ca2+ and CO32− to the surface of calcite crystals (1, -1, 0) decreased after the application of an electric field. By analysing the diffusion coefficient and radial distribution function of Ca2+ and CO32−, the electric field was shown to effectively prevents the diffusion and combination of to the calcite (1, -1, 0) crystal plane, which can effectively prevent the growth of calcium carbonate on the heat transfer surface. The experimental results showed that the fouling resistance is significantly reduced after electric field treatment. The results of scanning electron microscopy (SEM) and macroscopic analysis of fouling on heat transfer surface also show that electric field can effectively inhibit fouling. When the electric field intensity is 1300 V/m, it has the best anti-scaling effect. Therefore, the calculation results are basically consistent with the simulation conclusions.

Nonthermal inactivation of polyphenol oxidase in apple juice influenced by moderate electric fields: Effects of periodic on-off and constant exposure electrical treatments

Inactivation of polyphenol oxidase (PPO) in fresh apple juice was studied in moderate electric field (MEF) treatments at field strengths in the range of 85–110 V/cm. The apple juice was subjected to periodic on-off treatments at 50 °C and constant exposure MEF treatments at 50 and 65 °C using two different electro-processing devices, specially constructed for the purpose. PPO inactivation by the electric fields was determined with respect to the corresponding control (nofield) treatments. The application of periodic on-off treatments resulted in about 100% increase (P ≤ 0.05) of the thermal inactivation rate constant of PPO at 50 °C. A similar relative increase of the thermal inactivation rate constant was observed with the constant exposure MEF treatment at 50 °C. The electric field influence was improved significantly (P ≤ 0.05) in the constant exposure MEF treatment at 65 °C. Differences in electrical energy input among the MEF treatments were observed. Results indicate both the electric field strength and the treatment temperature play critical roles in enzyme inactivation by moderate electric fields. Industrial relevanceThis study shows polyphenol oxidase enzyme in fresh apple juice can be significantly inactivated by moderate electric fields applied at below thermal pasteurization temperatures. Therefore, moderate electric field treatment applications are beneficial for the minimally processed fruit and vegetable industry.

Explore the mechanism of pulsed electric field technology on improving the antioxidant activity of Leu-Tyr-Gly-Ala-Leu-Gly-Leu

In this study, the synthetic peptide Leu-Tyr-Gly-Ala-Leu-Gly-Leu (LYGALGL) derived from egg white was used as the research object. The structure - activity relationship was elucidated by cell experiment and structure determination. The results of cell experiment showed that the superoxide dismutase (SOD) activity and mitochondrial membrane potential (MMP) of LYGALGL were significantly increased by pulsed electric field (PEF) treatment, especially by 10 kV/cm field intensity treatment (P < 0.05). However, the content of reactive oxygen species (ROS) decreased significantly (P < 0.05). LYGALG treated with 10 kV/cm showed the highest antioxidant activity. The results of structure determination showed that the β-turn of LYGALGL increased, the random coil decreased, and the active hydrogen sites moved under 10 kV/cm treatment. The structure of LYGALGL was changed and the active site was exposed by PEF, thus improving the antioxidant activity of LYGALGL.

Effect of Pulsed Electric Fields on the Lipidomic Profile of Lipid Extracted from Hoki Fish Male Gonad.

Processing of hoki, a commercially important fish species, generates substantial quantities of co-products, including male gonad, which contains valuable lipids, such as phospholipids, that could be recovered and utilised. Hoki fish male gonads (HMG) were subjected to pulsed electric fields (PEF) treatment at varying field strengths (0.625, 1.25, and 1.875 kV/cm) and frequencies (25, 50, and 100 Hz), at a fixed pulse width of 20 μs. The total lipid was extracted using an ethanol-hexane-based (ETHEX) extraction method, and the phospholipid and fatty acid compositions were determined using 31P NMR and GC-FID, respectively. The total lipid yield was increased from 4.1% to 6.7% by a relatively mild PEF pre-treatment at a field strength of 1.25 kV/cm and frequency of 50 Hz. A higher amount of EPA (8.2%), DPA (2.7%), and DHA (35.7%) were obtained by that treatment, compared to both un-heated (EPA: 8%; DPA: 2.5%; DHA: 35.2%) and heat-treated controls (EPA: 7.9%; DPA: 2.5%; DHA: 34%). No significant changes to the content of the major phospholipids were observed. PEF pre-treatment under mild conditions has potential for improving the total lipid yield extracted from fish male gonad.

Application of pulsed electric field prior to vacuum drying: Effect on drying time and quality of apple tissue

The study aimed to determine the influence of a pulsed electric field (PEF) treatment on vacuum drying (VD) of apples and their selected quality parameters. The apples were treated with a PEF at 1 kV·cm–1 (with a variable amount of the specific energy input: 1, 3.5, and 6 kJ·kg&lt;sup&gt;–1&lt;/sup&gt;) before VD at 4 kPa (with a variable drying temperature: 40 °C, 55 °C, and 70 °C). The drying time, microstructure, retention of total phenolics (TPC) as well as the antioxidant activity of the obtained dried materials were studied. As a result of opening the cell structure of the apple tissues, the PEF significantly (P &amp;lt; 0.05) reduced the drying time – depending on the used process parameters – by 6–22%. Moreover, an increase in the drying temperature also shortened the drying time. The electroporation led to obtaining porous materials after drying, and with the higher amount of specific energy during the PEF pre-treatment that was applied, a higher porosity was observed in the dried apples. After the PEF-assisted VD, a significant (P &amp;lt; 0.05) decrease in the TPC (by 12–40%) and antioxidant activity (by 23–81%) were observed.

Pulsed electric field treatment for the stimulation of microorganisms: Applications in food production

The pulsed electric field (PEF) technology is a non-thermal processing technique usually used for microbial inactivation in food industries. The application of this technology at sub-lethal levels prior to or during the fermentation processes enhances the mass transfer and cell permeability. It could also cause changes in the genetic, metabolic, and physiological responses of microbial strains leading to an improvement in the fermentation process. Several studies reported the benefits of PEF on microorganisms including growth stimulation, an increase in the fermentation rates and product yields, and improvement in the metabolite extraction. All of these modifications could improve the organoleptic and nutritional properties of fermented food products. The purpose of this review is to summarise and discuss the main findings reported in the literature to date about the effect of PEFs applied at sub-lethal levels on microorganisms in the context of food processing.

Bioluminescent calcium mediated detection of nanosecond electroporation: Grasping the differences between 100 ns and 100 µs pulses

Electroporation is a phenomenon of transient or irreversible permeabilization of the cell membrane after pulsed electric field treatment. Fluorescent probes are frequently used to assess the extent of permeabilization, however, as an alternative, a D-luciferin oxidation-based method can be used. In this work, we have used sequences of a microsecond (1.3 kV/cm × 100 µs) and nanosecond (12.5 kV/cm × 100 ns) pulses to trigger various levels of cell permeabilization and assessed the differences in the response using a conventional fluorescent probe (YO-PRO-1 (YP)) and D-luciferin oxidation methodology. The nanosecond pulses (n = 5–100) have been delivered with 1 kHz repetition frequency, and the results were compared with 1 MHz protocols. Additionally, the effects of extracellular Ca2+ have been assessed. Various concentrations of CaCl2 (2, 5, and 10 mM) have been used, and it was shown that the bioluminescence of the cells after electroporation depends on extracellular calcium concentration. It was shown that the changes in bioluminescence signal could be used as a marker of cell membrane permeabilization on par with YP assay when calcium is added and thus, effectively employed for analysis of electroporation phenomenon in vitro both for nanosecond and microsecond pulses.

Electroporation and cell killing by milli- to nanosecond pulses and avoiding neuromuscular stimulation in cancer ablation

Ablation therapies aim at eradication of tumors with minimal impact on surrounding healthy tissues. Conventional pulsed electric field (PEF) treatments cause pain and muscle contractions far beyond the ablation area. The ongoing quest is to identify PEF parameters efficient at ablation but not at stimulation. We measured electroporation and cell killing thresholds for 150 ns–1 ms PEF, uni- and bipolar, delivered in 10- to 300-pulse trains at up to 1 MHz rates. Monolayers of murine colon carcinoma cells exposed to PEF were stained with YO-PRO-1 dye to detect electroporation. In 2–4 h, dead cells were labeled with propidium. Electroporation and cell death thresholds determined by matching the stained areas to the electric field intensity were compared to nerve excitation thresholds (Kim et al. in Int J Mol Sci 22(13):7051, 2021). The minimum fourfold ratio of cell killing and stimulation thresholds was achieved with bipolar nanosecond PEF (nsPEF), a sheer benefit over a 500-fold ratio for conventional 100-µs PEF. Increasing the bipolar nsPEF frequency up to 100 kHz within 10-pulse bursts increased ablation thresholds by < 20%. Restricting such bursts to the refractory period after nerve excitation will minimize the number of neuromuscular reactions while maintaining the ablation efficiency and avoiding heating.

A novel strategy to simultaneously enhance bioaccessible lipids and antioxidants in hetero/mixotrophic Chlorella vulgaris as functional ingredient

Microalgae are a promising source of polyunsaturated fatty acids as well as bioactive antioxidant compounds such as carotenoids, phenolics and tocopherols. However, the accumulation of these biomolecules is often promoted by conflicting growth conditions. In this study, a phased bioprocessing strategy was developed to simultaneously enhance the lipid and antioxidant amounts by tailoring nitrogen content in the cultivation medium and applying light stress. This approach increased the overall contents of total fatty acids, carotenoids, phenolics, and α-tocopherol in Chlorella vulgaris by 2.2-, 2.2-, 1.5-, and 2.1-fold, respectively. Additionally, the bioaccessibility of the lipids and bioactives from the obtained biomasses improved after pulsed electric field (5 μs, 20 kV cm−1, 31.8 kJ kg−1sus) treatment (up to +12%) and high-pressure homogenization (100 MPa, 5–6 passes) (+41–76%). This work represents a step towards the generation of more efficient algae biorefineries, thus expanding the alternative resources available for essential nutrients.