Pulsed Electric Field Strength Research Articles

High voltage pulsed electric field: A novel method for killing parasitic eggs on the surface of raisins

Aiming to address the issue of stored grain pests easily breeding during the process of dried fruits in Xinjiang, this study proposes a method and a device for killing raisin parasitic eggs based on a high-voltage pulsed electric field. A one-way test and a Box-Behnken central combination test were conducted to investigate the effects of high-voltage pulsed electric field strength and frequency on the unhatched rate and larval survival rate of Plodia interpunctella eggs on raisin surfaces. The experimental results were qualitatively and quantitatively analyzed using biooptical microscope observation and incubation at constant temperature and humidity post-treatment. The findings revealed that with an output voltage of 22.8 kV, the delivery speed of 0.024 m/s, and the electric field frequency of 3.8 Hz, the unhatched rate of the eggs was 68.14 % while the survival rate of the larvae was 20.36 %. These results can provide new insights for both theoretical development and system implementation regarding the use of high voltage pulsed electric fields for eliminating raisin surface eggs, as well as providing valuable academic references for field crop diseases and pests control strategies.

Effects of Pulsed Electric Field on Oil Extraction Rate and Tocopherol in Peony Seeds

Peony seed oil, known for its high nutritional value and low production yield, has become a crucial component in high-quality health products. Consequently, enhancing the extraction efficiency of peony seed oil has become an industry objective. Pulse electric field (PEF) technology, as a non-thermal extraction method, has shown promising advancements in improving plant oil yield by enhancing cell permeability. In this study, we designed a static parallel plate PEF treatment unit to process peony seed particles. By manipulating pulse voltage parameters, we investigated the effects of particle size and PEF strength on the oil yield. We also analyzed and evaluated tocopherol in the oil before and after treatment. The results demonstrated that PEF significantly increased the oil yield. Both treated and control groups exhibited gradually increased oil yields with decreasing particle size until reaching saturation at a certain particle size. Increasing voltage frequency did not have a significant impact on the oil yield; however, increasing voltage amplitude resulted in an optimal point for maximum oil yield. Analysis of oil composition indicated that PEF appropriately increased tocopherol content. These findings provide a foundation for further optimization of PEF parameters to assist in extracting peony seed oil and facilitate its industrial application.

Effects of Pulsed Electric Field Pretreatment on Black Tea Processing and Its Impact on Cold-Brewed Tea.

This study applied pulsed electric fields (PEFs) to accelerate the withering and drying processes during cold-brewed black tea production. PEF pretreatment was administered at 1.0, 1.5, and 2.0 kV/cm electric field strengths, combined with varying withering times from 8 to 12 hr. During the 12-hour withering process, the redness value (a*) and total color change (∆E) of PEF-treated leaves significantly increased (p < 0.05). Furthermore, the homogenous redness of tea leaves during fermentation depended on the PEF strength applied. In addition, PEF pretreatment remarkably reduced the drying time, up to a 50% reduction at a 2.0 kV/cm field strength. Additionally, the 2.0 kV/cm PEF-pretreated black tea exhibited a notable 42% increase in theaflavin (TF) content and a 54% increase in thearubigin (TR) content. Sensory evaluation scores were highest for black tea that received PEF pretreatment at 2.0 kV/cm. These findings highlight the significant potential of PEFs in enhancing the efficiency of withering and drying processes while positively impacting the physicochemical and sensory properties of cold-brewed black tea.

Mode and mechanism of water droplet breakup in oil under high-voltage and high-frequency pulsed electric fields

In industrial processes, the application of pulsed electric fields for electrostatic demulsification may cause droplet breakup, reducing demulsification efficiency. In this paper, a comprehensive approach combining microscopic experiment, theoretical derivation, and molecular dynamics simulation, were employed to explore the water droplet breakup in water-in-oil (W/O) under high-voltage and high-frequency pulsed electric fields. The results showed that droplet breakup would occur when the electrostatic tensile stress of the droplet surpassed the additional compressive stress. Three main modes of droplet breakup were observed: breakup at one end, breakup at both ends, and breakup in the middle part. By applying Maxwell stress equation, critical field strengths were derived to predict breakup locations. In the pulsed electric field, the droplets underwent a sequence of stretching, retraction, and eventual breakup. The formation and migration of hydrated ions was of crucial importance in the droplet breakup. A decrease in electrostatic attraction between H2O and an increase in dispersion attraction effect between H2O and C6H14 promoted the droplet breakup. The number of hydrogen bond inside the droplet was reduced, weakening the stability of droplet. The energy of electric field was transformed into the deflection of dipole moment and the velocity of water molecules. The time required for droplet breakup decreased when the pulsed electric field strength increased. The research findings in this paper uncovered the mechanism behind the breakup of water droplets in pulsed electric fields, and offered theoretical guidance for optimizing demulsification processes.

Effect of pulsed electric field pretreatment on mass transfer during hot air drying: Drying and rehydration properties of sweet potato

In this study, to investigate the effects of various pulsed electric field (PEF) strengths (0.5–2.5 kV/cm) on drying sweet potato, drying kinetics, mass transfer rate, rehydration kinetics, and microstructure of sweet potato during hot air drying were observed. After pretreatment of PEF, electric conductivity, and Z- index were increased as the strengths of PEF increased. The drying time was approximately 420 min for PEF at 1.5 kV/cm - 2.5 kV/cm and was almost 500 min for control group and the maximum values for moisture diffusivity and mass transfer was observed in 2.5 kV/cm. The shrinkage ratio and microstructure of sweet potatoes did not differ among groups; however, parenchyma cell membranes were empty and disrupted by PEF. The rehydration time decreased as the PEF strength increased, similar to the trend in drying times. PEF pretreatment resolves long-term hot air drying side effects such as quality deterioration and time requirements.

Resonant Excitation of the Ferroelectric Soft Mode by a Narrow-Band THz Pulse.

This study investigates the impact of narrow-band terahertz pulses on the ferroelectric order parameter in Ba0.8Sr0.2TiO3 films on various substrates. THz radiation in the range of 1-2 THz with the pulse width of about 0.15 THz was separated from a broadband pulse with the interference technique. The 375 nm thick BST film on a MgO (001) substrate exhibits enhanced THz-induced second harmonic generation when excited by THz pulses with a central frequency of 1.6 THz, due to the resonant excitation of the soft phonon mode. Conversely, the BST film on a Si (001) substrate shows no enhancement, due to its polycrystalline state. The 800 nm thick BST film on a MgO (111) substrate demonstrates the maximum of a second harmonic generation signal when excited by THz pulses at 1.8 THz, which is close to the soft mode frequency for the (111) orientation. Notably, the frequency spectrum of the BST/MgO (111) film reveals peaks at both the fundamental and doubled frequencies, and their intensities depend, respectively, linearly and quadratically on the THz pulse electric field strength.

Accelerated brining kinetics and NaCl distribution of Chinese cabbage (Brassica rapa ssp. pekinensis) using pulsed electric field

Brining is a representative processing method for the long-term preservation of food materials. We analyzed the effects of pulsed electric fields (PEF) at various strengths and brining solutions with two different NaCl concentrations (10 g/mL and 15 g/mL) at 25 °C for 12 h on Chinese cabbage. PEF had significant effects on mass transfer kinetics; k1 and k2 values were highest for PEF at 2.5 kV/cm, regardless of the brining solution concentration. Additionally, salinity and solid gain were highest for PEF at 2.5 kV/cm and gradually increased, depending on the strength of PEF. The hardness and cutting force were influenced by the PEF strength and NaCl concentration of the brining solution. The microstructure differed significantly between the PEF-pretreated and untreated samples. These results demonstrate that PEF can effectively reduce the brining time and NaCl concentration during brining process and may guide further research aimed at the practical application of PEF on food processing.

Combination of pulsed electric field and pH shifting improves the solubility, emulsifying, foaming of commercial soy protein isolate

In this study, the effects of a new dual modification method, pulsed electric field (PEF) and pH shifting treatment, on the solubility, emulsifying and foaming properties of commercial soy protein isolate (SPI) were investigated. Results showed that the combination of PEF and pH shifting treatment, particularly at moderate PEF strength (10 kV/cm) and alkaline conditions (pH 11), facilitated protein structure unfolding and formation of smaller aggregates, substantially enhancing the solubility of SPI from 26.06% to 70.34%. Higher flexibility, surface hydrophobicity, and free sulfhydryl content were also found in the modified SPI, which boosted interfacial activity and significantly enhanced emulsifying and foaming properties. In alkaline environments, the enhanced functional properties of SPI at moderate PEF strength may be attributed to the appropriate oxidation of proteins by free radicals produced by electrochemical processes and the additional unfolding of protein conformations by polarization. The functional characteristics of SPI were decreased by an increase in PEF strength (20 kV/cm), which may be due to the tendency of the protein to aggregate and undergo excessive oxidation. This work may provide an effective methodological and theoretical basis for the modification of SPI by combining PEF and pH shifting treatment. • PEF combined with pH shifting treatment efficiently improved the solubility of SPI. • The treated SPI showed dramatic enhancement in emulsifying and foaming properties. • Enhanced unfolding in pH shifted SPI were observed after PEF introduction. • PEF-induced polarization and proper oxidation enhanced the functional property of SPI.

Polysaccharides in Selenium-Enriched Tea: Extraction Performance under Innovative Technologies and Antioxidant Activities.

Pulsed electric fields (PEF) and ultrasonic-assisted extraction (UE) were applied to improve the extraction performance of selenium-enriched tea polysaccharides (Se−TPSs) in mild conditions. Two combined extraction processes were investigated: (1) PEF strength at 10 kV/cm followed by conventional extraction (CE) at 50 °C for 60 min and (2) PEF+UE (PEF strength at 10 kV/cm followed by UE at 400 W for 60 min). The optimal extraction yields, and energy consumption rates were obtained at 36.86% and 41.53% and 78.78 kJ/mg and 133.91 kJ/mg, respectively. The Se−TPSs were analyzed and characterized by GPC, UV, and FT-IR, which evidenced the structural stability of the Se−TPSs during the extraction processes. It was found that PEF and UE could reduce the particle size diameter of the Se−TPS extract, as well as the proportion of uronic acid. Moreover, PEF could increase the selenium content in the Se−TPS extract by 160.14% due to a lower extraction temperature compared to conventional extraction. The antioxidant activities of the Se−TPSs in vitro were investigated using OH, , and scavenging experiments, as well as a total antioxidant ability evaluation. It was found that the antioxidant activity of the Se−TPSs obtained using PEF2+CE2 was relatively high due to the potential synergistic effect between the selenium and polysaccharides. Based on these results, we speculate that PEF2+CE2 was the best extraction process for the Se−TPSs. Furthermore, this research indicates the application of selenium-enriched tea for functional food production.

Experimental and model study for liquid–liquid extraction of conductive nanofluid drops under low voltage pulsed electric fields

Mass transfer of conductive nanofluid drops in liquid–liquid extraction was investigated under low voltage pulsed electric fields. Cu and Ag nanoparticles were synthesized and characterized by different methods. The chemical system of kerosene–acetic acid–water was used in which mass transfer resistance exists mainly in the kerosene and the nanofluids of this solvent were dispersed phase drops. A column equipped with parallel plate electrodes was employed in which different pulsed electric field strengths of 2–16 V/cm and frequencies of 100–1000 Hz were established by means of an electric field generator. Terminal velocity of drops obeyed the Grace model and amazing mass transfer enhancements of 136.2 and 154.1% were achieved upon applying the pulsed electric fields. The well-known Kumar and Hartland correlation sufficiently reproduced the mass transfer coefficient data in relation to a developed correlation for the enhancement factor in terms of dimensionless influencing parameters.

Effects of ionic liquids and pulsed electric fields on the extraction of antioxidants from green asparagus roots

SummaryAsparagus officinalis root (AR) contains valuable bioactive compounds that have beneficial health properties. The aim of this study was to optimize the extraction of polyphenols and flavonoids in green AR using two novel technologies; pulsed electric field (PEF) and ionic liquids (IL). Further, the antioxidant activity of the obtained extracts was determined. The total polyphenol content, total flavonoid content (TFC), and antioxidant activity (2,2‐diphenyl‐1‐picrylhydrazyl, oxygen radical absorbance capacity and Ferric reducing/antioxidant power assays) were determined. The PEF conditions (PEF strength of 1.6 kV/cm, frequency of 200 Hz and pulse width of 20 µs) resulted in a higher extraction yield as compared to conventional solvent extraction, but had lower antioxidant activities. The optimal conditions for IL extraction were by using 0.5% 1‐butyl‐3‐methylimidazolium chloride at a solid: liquid (S:L) ratio of 1:10 for four min. The IL extraction resulted in a total of 122 mg RE/ mL TFC which was 70 to 80 folds more than the TFC obtained by PEF. The IL extracts had higher TFC and antioxidant activity than PEF, but the safety of the ILs need further research.

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.

High harmonics generation in gases near the gratings: towards the spectrum enhancement and enrichment

The problem of harmonic generation efficiency (as an example of non-linear optical phenomena) increasing by atomic media near the surface of a one-dimensional metal diffraction grating under conditions of plasmon resonance excitation is considered. The local field enhancement factor dependences on diffraction grating profile are studied. Spatial distribution of the femtosecond pulse electric field strength over the grating surface under conditions of plasmon resonance excitation is simulated. Generated harmonic efficiency enhancement and photoemission spectra enrichment (due to laser field strength amplification near the grating) are discussed.

Using the response surface methodology to establish the optimal conditions for preserving bananas (Musa acuminata) in a pulsed electric field and to decrease browning induced by storage at a low temperature

In this study, a pulsed electric field (PEF) was used to establish the preservation conditions of bananas (Musa spp.) and explore the effect on chilling injury (CI) inhibition. The response surface methodology (RSM) demonstrated that the PEF strength of 50 kV m−1 has a better inhibition effect on browning; however, adverse effects are caused when the PEF strength exceeds 100 kV m−1 in comparison with untreated group. The optimal conditions established using RSM were PEF strength 32 kV m−1, frequency 278 Hz, treatment time 32 min and width 600 μs, which can effectively inhibit the degree of banana browning by 131.6%. Further storage tests indicated that PEF could effectively improve fruit weight loss (18.91%), firmness (10.91%), browning and other changes associated with quality by maintaining the levels of total chlorophyll, carotenoids and ascorbic acid. This suggests that PEF has the potential to delay the CI of bananas stored at low temperatures and can maintain high fruit quality.

Binding affinity of curcumin to bovine serum albumin enhanced by pulsed electric field pretreatment

The present study investigated the effect of pulsed electric field (PEF) pretreatment on the interaction between bovine serum albumin (BSA) and curcumin. Fluorescence quenching results showed that proper PEF pretreatment significantly increased the binding affinity of curcumin and BSA, the binding constant increased by 6.77 times under the conditions of 15 kV/cm for 0.51 ms. However, at higher PEF strength (≥25 kV/cm) and longer processing time (≥0.68 ms), the binding affinity was weakened. PEF pretreatment made the protein structure more disordered and induced partial unfolding of BSA, exposing more hydrophobic regions, thereby increasing the binding affinity to curcumin. PEF-treated BSA (PBSA) possessed better encapsulation efficiency (95.19%) and loading capacity (5.25 mg/g) for curcumin, and the storage stability of curcumin were enhanced by the formation of a complex with PBSA. This study provides new insights into the design of BSA-based delivery systems for curcumin and other hydrophobic nutrients.

Effect of Pulsed Electric Field (PEF) on Bacterial Viability and Whey Protein in the Processing of Raw Milk

There is growing concern regarding the nutritional value of processed food products. Although thermal pasteurization, used in food processing, is a safe method and is widely applied in the food industry, food products lack quality and nutritional value because of the high temperatures used during pasteurization. In this study, the effect of pulsed electric field (PEF) processing on whey protein content and bacterial viability in raw milk was evaluated by changing the PEF strength and number of pulses. For comparison, traditional pasteurization techniques, such as low-temperature long-time (LTLT), ultra-high temperature (UHT), and microfiltration (MF), were also tested for total whey protein content, bacterial activity, and coliforms. We found that, after treatment with PEF, a significant decrease in total bacterial viability of 2.43 log and coliforms of 0.9 log was achieved, although undenatured whey protein content was not affected at 4.98 mg/mL. While traditional pasteurization techniques showed total bacterial inactivation, they were detrimental for whey protein content: β-lactoglobulin was not detected using HPLC in samples treated with UHT. LTLT treatment led to a significant decrease of 75% in β-lactoglobulin concentration; β-lactoglobulin content in milk samples treated with MF was the lowest compared to LTLT and UHT pasteurization, and ~10% and 27% reduction was observed.

Pulsed electric field combined with microwave-assisted extraction of pectin polysaccharide from jackfruit waste

The present methodology uses the combination of pulsed electric fields (PEF) and microwave-assisted extraction (MAE) of pectin from the jackfruit wastes. Two optimization tools such as Box-Behnken design (BBD) and artificial neural network (ANN) were used to study the extraction yields. The optimized operating conditions obtained after desirability analysis were PEF strength (11.99 kV/cm), PEF treatment time (5.47 min), followed by MAE at power density (647.30 W/g) and time of exposure (5.00 min). From the optimization results, the R2 values of BBD ranged from 0.89 to 0.98 as well as the SSE (sum of squared error) values varied across 0.076 to 0.781 whereas R2 values of ANN fluctuated around 0.95 to 0.99 and MSE (mean squared error) values varied from 0.008 to 0.1. It was observed the ANN was found to be more superior in execution than the BBD model. The extracted pectin was analyzed for structural and functional properties with the comparison to conventionally extracted pectin. The degree of esterification and methoxyl percentage of PEF and MAE pectin was less than the conventionally extracted pectin. The experimental and predicted values were similar for the pectin yield (%), but a higher prediction rate was observed in ANN modelling than BBD. Scanning Electron Micrographs showed an increased rupture and severing of parenchymal cells attributing to enhance extraction yields. Therefore, it can be concluded that the pulsed electric field treatment followed by microwave-assisted extraction resulted in higher pectin extraction with enhanced functional properties than the conventional method.

Assessment of plant tissue disintegration degree and its related implications in the pulsed electric field (PEF)–assisted aqueous extraction of betalains from the fresh red beetroot

In this study, we performed the pulsed electric field (PEF)-assisted aqueous extraction of betalains from fresh red beetroot, simultaneously evaluating a disintegration degree of red beetroot tissue. The extraction results showed that the application of 3 pulses (1 Hz) with 100 μs duration and 2.0 kV/cm pulse strength (delivering total specific energy of 2.53 kJ/kg) resulted in extraction up to ~70% (extracted for 1 h at 22 °C) of total betalains. It was observed that at low specific energy inputs (0.8 and 2 kJ/kg – 0.5, 1.0, 1.5 and 2.0 kV/cm), the PEF treatment duration has a significant effect on the extraction yield of betalains. We show that comparing the efficiency of PEF treatments with different PEF strengths and durations, but the same specific energy inputs (0.8, 2.0, and 4.0 kJ/kg), higher permeabilization index (Zp) does not refer to a higher extraction yield of betalains. Industrial relevancePEF-assisted aqueous extraction of betalains from the fresh red beetroot is effective, energy favourable and environmentally friendly method and could serve as an alternative to the conventional extraction techniques. Our study shows that the extraction yield of betalains is better reflected by measurements of supernatant conductivity rather than Zp.

Peculiarities of Neurostimulation by Intense Nanosecond Pulsed Electric Fields: How to Avoid Firing in Peripheral Nerve Fibers.

Intense pulsed electric fields (PEF) are a novel modality for the efficient and targeted ablation of tumors by electroporation. The major adverse side effects of PEF therapies are strong involuntary muscle contractions and pain. Nanosecond-range PEF (nsPEF) are less efficient at neurostimulation and can be employed to minimize such side effects. We quantified the impact of the electrode configuration, PEF strength (up to 20 kV/cm), repetition rate (up to 3 MHz), bi- and triphasic pulse shapes, and pulse duration (down to 10 ns) on eliciting compound action potentials (CAPs) in nerve fibers. The excitation thresholds for single unipolar but not bipolar stimuli followed the classic strength–duration dependence. The addition of the opposite polarity phase for nsPEF increased the excitation threshold, with symmetrical bipolar nsPEF being the least efficient. Stimulation by nsPEF bursts decreased the excitation threshold as a power function above a critical duty cycle of 0.1%. The threshold reduction was much weaker for symmetrical bipolar nsPEF. Supramaximal stimulation by high-rate nsPEF bursts elicited only a single CAP as long as the burst duration did not exceed the nerve refractory period. Such brief bursts of bipolar nsPEF could be the best choice to minimize neuromuscular stimulation in ablation therapies.

Transient Polarization Reversal using an Intense THz Pulse in Silicon‐Doped Lead Germanate

The processes of dynamic polarization switching induced by the strong electric field of a nearly single‐cycle terahertz (THz) pulse are studied in a classical ferroelectric silicon‐doped lead germanate single crystal, Pb5(Ge0.74Si0.26)3O11, in THz pump–second‐harmonic‐generation (SHG) probe geometry depending on the pulse electric field strength (0.05–15.6 MV cm−1). Since the pump parameters correspond to the region of phonon excitations for a given material, THz‐induced polarization is explained by a dynamic change in the ferroelectric order parameter. Numerical solutions of the Landau–Khalatnikov equation using the thermodynamic potential constants for this material show that the effect of powerful THz pulses leads to polarization modulations and a strong nonlinear response, and is in good agreement with the experimental results. Oscillations of the nonlinear optical response after the end of the THz pulse are found, which can be associated with the excitation of the phonon mode in the crystal.