Intensity Pulsed Electric Fields Research Articles

Effect of freeze-thaw and PEF pretreatments on the kinetics and microstructure of convective and ultrasound-assisted drying of orange peel

The main waste generated by juice industry comprises orange peels, which have a great upcycling potential once stabilized. Drying is the most used method for this purpose, but the high energy consumption prompts interest in its intensification. This study assessed the influence of freeze-thaw and pulsed electric field (PEF) pretreatments in conventional and airborne ultrasound-assisted drying (50 °C) of orange peels. None of these pretreatments alone got to reduce processing times significantly, but combined with ultrasound-assisted drying produced a significant shortening of the process. This was particularly important in the lower intensity PEF pretreatment tested (0.33 kJ/kg), indicating the existence of optimum conditions to carry out the pretreatments. Microstructure analysis revealed that the application of ultrasound during drying led to better preservation of the sample structure. Thus, the integration of pretreatment techniques to ultrasound-assisted drying may not only shorten the process but also help to preserve the original structure.

In Vitro Assay Development to Study Pulse Field Ablation Outcome Using Solanum Tuberosum.

Exposing cells to intense and brief electric field pulses can modulate cell permeability, a phenomenon termed electroporation. When applied in medical treatments of diseases like cancer and cardiac arrhythmias, depending on level of cellular destruction, it is also referred to as irreversible electroporation (IRE) or Pulsed Field Ablation (PFA). For ablation device testing, several pulse parameters need to be characterized in a comprehensive manner to assess lesion boundary and efficacy. Overly aggressive voltages and application numbers increase animal burden. The potato tuber is a widely used initial model for the early testing of electroporation. The aim of this study is to characterize and refine bench testing for the ablation outcomes of PFA in this simplistic vegetal model. For in vitro assays, several pulse parameters like voltage, duration, and frequency were modulated to study effects not only on 2D ablation area but also 3D depth and volume. As PFA is a relatively new technology with minimal thermal effects, we also measured temperature changes before, during, and after ablation. Data from experiments were supplemented with in silico modeling to examine E-field distribution. We have estimated the irreversible electroporation threshold in Solanum Tuberosum to be at 240 V/cm. This bench testing platform can screen several pulse recipes at early stages of PFA device development in a rapid and high-throughput manner before proceeding to laborious trials for IRE medical devices.

Effects of pulse repetition rate in static electrochemotherapy models

Electroporation alters cell membrane structure and tissue electrical properties by short and intense pulsed electric fields (PEF). Static mathematical models are often used to explain the change in electrical properties of tissues caused by electroporation. Electric pulse repetition rate may play an important role, as tissue dielectric dispersion, electroporation dynamics, and Joule heating may affect the electrical properties. In this work, we investigate the effects on the magnitude of the electric current when the repetition rate of the standard electrochemotherapy protocol is increased. Liver, oral mucosa, and muscle tissues were studied. Ex vivo animal experiments show that the magnitude of the electric current increases when the repetition rate is changed from 1 Hz to 5 kHz (10.8% for liver, 5.8% for oral mucosa, and 4.7% for muscle). Although a correction factor could reduce the error to less than 1%, dynamic models seem to be necessary to analyze different protocol signatures. Authors should be aware that static models and experimental results can only be compared if they use exactly the same PEF signature. The repetition rate is a key information to consider in the pretreatment computer study because the current at 1 Hz PEF differs from a 5 kHz PEF.

Application of moderate intensity pulsed electric fields in red prickly pears and soymilk to develop a plant-based beverage with potential health-related benefits

Through the last years consumers have shown a growing interest in minimally processed foods with clean labels that not only satisfy basic nutrition but also provides health-benefits. This has motivated scientists and technologists to find optimal combination of ingredients and novel technologies to produce functional products with attractive sensory properties. Red prickly pears (RPP) and soymilk (SM) have been recognized as rich sources of antioxidant compounds with health properties. Moderate intensity pulsed electric fields (MIPEF) application in plant-based foods increases phytochemicals content through stress induction or improved extraction yields. Hence, the aim of this work was to enhance the bioactive compounds content of RPP and SM by MIPEF and use them for the development of a plant-based beverage with potential health-benefits. Results indicated that MIPEF-processing increased the bioactive compounds content of RPP and SM, resulting in a plant-based beverage with higher concentration of total phenolic compounds (16%), betalains (7.2%) and isoflavones (7.4%) than the control-beverage. Furthermore, MIPEF application to the ingredients did not affect physicochemical attributes of the beverage, obtaining an appealing product with potential health-attributes. Industrial relevancePulsed electric fields processing at moderate intensities (<5 kV/cm) might be a potential way to enhance the phytochemicals concentration of plant-based ingredients used for the development of beverages with clean-labels, minimally processed and potential health benefits. This kind of products could satisfy current consumers' demand in special situations of health. However, further research must continue to better understand the mechanisms occurred during processing and to find the best processing parameters for different raw materials.

Determination of lethal electric field threshold for pulsed field ablation in ex vivo perfused porcine and human hearts.

Pulsed field ablation is an emerging modality for catheter-based cardiac ablation. The main mechanism of action is irreversible electroporation (IRE), a threshold-based phenomenon in which cells die after exposure to intense pulsed electric fields. Lethal electric field threshold for IRE is a tissue property that determines treatment feasibility and enables the development of new devices and therapeutic applications, but it is greatly dependent on the number of pulses and their duration. In the study, lesions were generated by applying IRE in porcine and human left ventricles using a pair of parallel needle electrodes at different voltages (500-1500 V) and two different pulse waveforms: a proprietary biphasic waveform (Medtronic) and monophasic 48 × 100 μs pulses. The lethal electric field threshold, anisotropy ratio, and conductivity increase by electroporation were determined by numerical modeling, comparing the model outputs with segmented lesion images. The median threshold was 535V/cm in porcine ((N = 51 lesions in n = 6 hearts) and 416V/cm in the human donor hearts ((N = 21 lesions in n = 3 hearts) for the biphasic waveform. The median threshold value was 368V/cm in porcine hearts ((N = 35 lesions in n = 9 hearts) cm for 48 × 100 μs pulses. The values obtained are compared with an extensive literature review of published lethal electric field thresholds in other tissues and were found to be lower than most other tissues, except for skeletal muscle. These findings, albeit preliminary, from a limited number of hearts suggest that treatments in humans with parameters optimized in pigs should result in equal or greater lesions.

Pulsed electric field (PEF) application on wheat malting process: Effect on hydration kinetics, germination and amylase expression

Wheat malt has been widely used in food industry as an important source of endogenous enzymes, such as amylases. However, malting is a time-consuming process. Thus, this work proposed pulsed electric field (PEF) application to enhance wheat hydration, germination and amylase expression. Two-step hydration of Hendrix wheat variety was studied. PEF treatments (3 kV·cm−1; total energy applied of 9.9 and 19.8 kJ·kg−1) were applied with wheat in the water at the beginning or after the first hydration cycle. Hydration curves were accurately described by the Weibull exponential model (R2adj > 0.98). The more intense PEF treatments enhanced hydration rate (25%), water holding capacity (15%) and germination parameters when applied before the first hydration cycle. PEF enhanced α- and β-amylase activity by up to 104% and 25%, respectively, compared to control. Therefore, PEF can be used as a clean emerging technology to improve the malting process and malt quality. Industrial relevanceGrowing concerns have gained attention regarding the use of synthetic enzymes or higher amounts of natural resources to perform enzymatic process to food applications. Malting cereals represents a clean technology to provide natural enzymes from natural resources, even though it is still considered a time- and energy-consuming method. In this sense, the use of pulsed electric fields (PEF) demonstrated to be a green and efficient technique to enhance the overall wheat malting process. Besides improving the process kinetics, the enzymatic activity and, thus, the quality of the final malt can be also improved. Because of that, malting producers can process wheat more rapidly to obtain more efficient ingredients when incorporating PEF to their processes. On the other hand, brewery and baking sector can use wheat malt stimulated by PEF as raw material with comparable technological effects as conventional malts, but in lower amounts instead.

Understanding the effect of meat electrical conductivity on Pulsed Electric Field (PEF) process parameters and the ability of PEF to enhance the quality and shorten sous vide processing for beef short ribs

The aim of this research was to investigate how the electrical conductivity of short ribs affected Pulsed Electric Field (PEF) process parameters and the ability of PEF to enhance their quality and reduce sous vide (SV) processing time. Short ribs with different range of electrical conductivity (3–6, 6–9, and 9–12 mS/cm) values were treated using input voltage of 10 kV, pulse width of 20 µs, pulse frequency of 50 Hz and pulse number, of either 1600 (low intensity PEF/LPEF) or 5200 (high intensity PEF/HPEF), followed by SV processing at 60 °C for either 24 or 36 h. The quality parameters assessed were cooking loss (%), Texture Profile Analysis (TPA) parameters, and Commission Internationale d’Eclairage (CIE) L*a*b* colour parameters. There was a variation in electrical conductivity of short ribs according to the position of the bone in the short rib, which demonstrated good congruence with the distribution of fat and connective tissue. SV processing with or without PEF pre-treatment did not have a significant effect (p > 0.05) on cooking loss or CIE L*a*b* colour parameters. Short ribs with a medium conductivity (6–9 mS/cm) had a significantly lower hardness after high intensity PEF followed by SV for 24 h, whilst short ribs with an average conductivity of 3–6 and 9–12 mS/cm required longer SV time (up to 36 h) and had a significantly lower hardness compared to non PEF pre-treated samples. TPA values of short ribs treated with the same PEF intensity and SV processing parameters were comparable regardless of the short ribs initial electrical conductivity, which indicates that PEF treatment could ameliorate the biological electrochemical variability inherent to short ribs and PEF could be the potential tool to decrease their SV processing time and enhance their tenderness.

Effect of Pasteurization by Moderate Intensity Pulsed Electric Fields (PEF) Treatment Compared to Thermal Treatment on Quality Attributes of Fresh Orange Juice.

Novel pulsed electric field (PEF) process conditions at moderate electric field strength and long pulse duration have recently been established to obtain microbial inactivation. In this study, the effect of these PEF conditions (E = 0.9 and 2.7 kV/cm, with pulse duration 1000 µs) at variable maximum temperatures was evaluated on quality attributes of freshly squeezed orange juice. Results were compared to orange juice that received no treatment or a mild or severe thermal pasteurization treatment. No differences for pH and soluble solids were found after application of any treatment, and only small differences were observed for color and vitamin C content (ascorbic acid and dehydroascorbic acid) after processing, mainly for conditions applied at higher temperature. Variations in the maximum temperatures of the PEF and thermal processes led to differences in flavor compounds and the remaining activity of pectinmethylesterase (PME). At PEF conditions with a maximum temperature of 78 °C or higher, PME activity levels were below a critical value, meaning that the cloud is stable. At this temperature volatiles associated with fresh juice (such as octanal and nonanal) are statistically identical to untreated juice, while they are statistically distinguishable from thermal treated. This papers demonstrates the potential of using moderate intensity PEF as an adequate alternative to thermal pasteurization of orange juice with a better retention of the fresh flavor.

Texture and in vitro starch digestion kinetics of French fries produced from potatoes (Solanum tuberosum L.) pre-treated with pulsed electric fields

The impact of Pulsed Electric Field (PEF) processing pre-treatment on the texture and kinetics of in vitro starch digestibility of French fries made from two potato cultivars (Solanum tuberosum L.) containing dry matter content ranging from 19 to 22% was investigated. Whole and steam-peeled potato tubers were treated with a pilot scale PEF unit (electric field strength of 1.1 and 1.9 kV/cm with energy input <10 kJ/kg or ∼50 kJ/kg). This trial was carried out in a commercial French-fry plant using an industrial scale cutter, blancher, fryer and blast-freezer to prepare the frozen par-fried French fry samples. After subsequent final batch frying of the frozen fries, at 180 °C for 3 min to mimic the typical preparation practice at restaurant, retail and household, the outer crust of the fries produced from PEF-treated potatoes was significantly harder (9.4–16.3 N) than crust produced from untreated potatoes (6.9–8.5 N). High intensity (1.9 kV/cm with energy input ∼50 kJ/kg) PEF processing was found to cause defects (i.e. hollowness in the internal core) in the fries. A fractional conversion model was a good fit for the starch digestion kinetics of all French fry samples during the small intestinal phase (based on standardised INFOGEST static in vitro digestion assay). A lower % of total starch hydrolysis was predicted for French fries produced from high dry matter (>21%) tubers pretreated with PEF at electric field strength of 1.9 kV/cm. The findings generated in this study demonstrate PEF pretreatment may influence the texture of French fries and the extent of starch digestion that occurs.

Models of electroporation and the associated transmembrane molecular transport should be revisited

Electroporation has become a powerful tool for nonviral delivery of various biomolecules such as nucleic acids, proteins, and chemotherapeutic drugs to virtually any living cell by exposing the cell membrane to an intense pulsed electric field. Different multiphysics and multiscale models have been developed to describe the phenomenon of electroporation and predict molecular transport through the electroporated membrane. In this paper, we critically examine the existing mechanistic, single-cell models which allow spatially and temporally resolved numerical simulations of electroporation-induced transmembrane transport of small molecules by confronting them with different experimental measurements. Furthermore, we assess whether any of the proposed models is universal enough to describe the associated transmembrane transport in general for all the different pulse parameters and small molecules used in electroporation applications. We show that none of the tested models can be universally applied to the full range of experimental measurements. Even more importantly, we show that none of the models has been compared to sufficient amount of experimental data to confirm the model validity. Finally, we provide guidelines and recommendations on how to design and report experiments that can be used to validate an electroporation model and how to improve the development of mechanistic models.

The Application and Optimization of HIPEF Technology in the Processing of Juice from Strawberries Harvested at Two Stages of Ripeness.

The aim of this study was to investigate the influence of high intensity pulsed electric field (HIPEF) technology on the stability of total phenols, anthocyanins, hydroxycinnamic acids, flavonols, and condensed tannins in strawberry juices (Fragaria x ananassa Duch. cv. ‘Albion’) with different ripening stages (75% and 100%) and stored at +4 °C for 7 days. The HIPEF parameters studied were: (i) electric field strength (40 and 50 kV cm−1), (ii) frequency (100 and 200 Hz), and (iii) treatment duration (3 and 6 min). Of the HIPEF parameters studied, electric field strength and frequency had a statistically significant effect on the content of all phenolic compounds. Treatment duration showed no statistically significant effects on phenolic compounds except for flavonols and condensed tannins. Storage had a positive effect on the stability of most of the phenolic compounds, with the exception of flavonols. Optimization of HIPEF processing showed that strawberry samples at both ripeness levels were suitable for HIPEF treatment to obtain functional fruit juices with a high content of polyphenols.

Generation of Intense Pulsed Electric Fields in a Large Volume of Water Verified Using Kerr Effect Diagnostics

A pulsed power system for generating intense pulsed electric fields (PEFs) in a very large volume of water was designed, manufactured, and tested as a first step toward the proof-of-principle demonstration of a novel noninvasive prepacked food processing operation. The MV-class system described in this article is based on the Tesla transformer technology and is capable of producing PEFs of 100 kV/cm in water, in a volume approaching 1 L. The electric field distribution in the processing water tank was obtained using an electrostatic solver, benchmarked using a Kerr effect arrangement. This article presents the most important experimental data, followed by a detailed electric field analysis and suggestions for the way ahead.

Effect of moderate intensity pulsed electric field on shelf-life of chicken breast meat

ABSTRACT 1. Moderate intensity pulsed electric field (MIPEF) is a fairly new research topic for microbial inactivation on muscle foods. In this study, indirect application of MIPEF (2.5 kV/cm, 4.67 kV/cm, 7 kV/cm) was evaluated in terms of the growth of some pathogenic bacteria and the quality characteristics of chicken breast meat during cold storage (4°C). 2. This study was conducted in two stages. In the first stage, pure cultures of S. enteritidis, P. aeruginosa, S. aureus, L. monocytogenes, E. coli and C. jejuni were inoculated in broth and stored in a refrigerator at 4°C under MIPEF. Both E. coli and C. jejuni showed a remarkable resistance to MIPEF under 4.67 kV/cm and 7 kV/cm, respectively. 3. In the second stage, MIPEF was applied to packaged chicken breast samples. The limit for total mesophilic aerobic bacteria (TMAB) count was exceeded in 4.67 and 7 kV/cm applied groups 2 d later than seen in the control group (C). Almost 2 log differences were determined for total coliform bacteria in 4.67 and 7 kV/cm applied groups as compared to C (P < 0.05). Inoculated P. aeruginosa count remained the same, whereas L. monocytogenes growth was promoted by 4.67 kV/cm (P < 0.05). 4. pH value, CIE L*, b*, C* colour values of chicken breast fillets were not affected by MIPEF application while ΔE values showed the maximum change in the C group. 5. This study demonstrated that improved shelf-life of chicken breast fillets was provided by moderate intensity DC-pulses in combination with cold storage.

Spatial mechanistic modeling for prediction of 3D multicellular spheroids behavior upon exposure to high intensity pulsed electric fields

&lt;abstract&gt; &lt;p&gt;The objective of this work was to investigate the growth specificities of cancer cells spheroids subjected to pulsed electric field. Multicellular HCT-116-GFP spheroids were exposed to different electric field intensities and the volume of multicellular spheroids was monitored by fluorescence and bright field microscopy. Thanks to an advanced mathematical model, based on differential equations and well-adapted estimation strategies, our modeling enables us to characterize the multicellular spheroids growth after permeabilizing pulsed electric field. In particular, we identify the percentage of cells which are destroyed and the percentage of cells which exhibit an altered growth pattern for different magnitudes of the electric field. We also quantify the growth resumption upon reversible and partially irreversible electroporation. Our preliminary results provide a first quantification of the impact of electroporation on multicellular spheroids growth, and suggest a booming growth of partially irreversible electric pulses, leading to an accelerated regrowth.&lt;/p&gt; &lt;/abstract&gt;

Efficient ionization of two-dimensional excitons by intense single-cycle terahertz pulses

External electric fields are highly attractive for dynamical manipulation of excitons in two-dimensional materials. Here, we theoretically study the ionization of excitons in monolayer transition metal dichalcogenides (TMDs) by intense pulsed electric fields in the terahertz (THz) regime. We find that THz pulses with realistic field strengths are capable of ionizing a significant fraction of photogenerated excitons in TMDs into free charge carriers. Short THz pulses are therefore an efficient, non-invasive method of dynamically controlling the free carrier concentration in monolayer TMDs, which is useful for applications such as THz modulators. We further demonstrate that exciton ionization probabilities should be experimentally measurable by comparing free carrier absorption before and after the THz pulse. Detailed results are provided for different TMDs in various dielectric environments.

Integrating flexible electronics for pulsed electric field delivery in a vascularized 3D glioblastoma model

Glioblastoma is a highly aggressive brain tumor, very invasive and thus difficult to eradicate with standard oncology therapies. Bioelectric treatments based on pulsed electric fields have proven to be a successful method to treat cancerous tissues. However, they rely on stiff electrodes, which cause acute and chronic injuries, especially in soft tissues like the brain. Here we demonstrate the feasibility of delivering pulsed electric fields with flexible electronics using an in ovo vascularized tumor model. We show with fluorescence widefield and multiphoton microscopy that pulsed electric fields induce vasoconstriction of blood vessels and evoke calcium signals in vascularized glioblastoma spheroids stably expressing a genetically encoded fluorescence reporter. Simulations of the electric field delivery are compared with the measured influence of electric field effects on cell membrane integrity in exposed tumor cells. Our results confirm the feasibility of flexible electronics as a means of delivering intense pulsed electric fields to tumors in an intravital 3D vascularized model of human glioblastoma.

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.

The role of ESCRT-III and Annexin V in the repair of cell membrane permeabilization by the nanosecond pulsed electric field

Exposure of living cells to intense nanosecond pulsed electric field (nsPEF) increases membrane permeability to small solutes, presumably by the formation of nanometer-size membrane lesions. Mechanisms responsible for the restoration of membrane integrity over the course of minutes after nsPEF have not been identified. This study explored if ESCRT-III and Annexin V calcium-dependent repair mechanisms, which play critical role in resealing large membrane lesions, are also activated by electroporation and contribute to the membrane resealing. The extent of membrane damage and the time course of resealing were monitored by the time-lapse imaging of propidium (Pr) uptake in human cervical carcinoma (HeLa) cells exposed to trains of 300-ns PEF. The removal of the extracellular Ca2+ slowed down the resealing, although did not prevent it. Recruitment of CHMP4B protein, a component of ESCRT-III complex, to the electroporated plasma membrane was not observed, thus providing no evidence for possible contribution of the macro-vesicle shedding mechanism. In contrast, silencing the AnxA5 gene impaired resealing and reduced the viability of nsPEF-treated cells. We conclude that Annexin V but not ESCRT-III was involved in the repair of HeLa cells permeabilized by 300-ns stimuli, but it was not the only and perhaps not the main repair mechanism.

A wideband picosecond pulsed electric fields (psPEF) exposure system for the nanoporation of biological cells

The effects and mechanisms of ultrashort and intense pulsed electric fields on biological cells remain some unknown. Especially for picosecond pulsed electric fields (psPEF) with a high pulse repetition rate, electroporation or nanoporation effects could be induced on cell membranes and intracellular organelle membranes. In this work, the design, implementation, and experimental validation of a wideband psPEF exposure system (WPES) is reported, comprising picosecond pulser and wideband biochip, for the in vitro exposure of suspended cells to high-intensity psPEF. Excited by repetitive picosecond pulses (the duration of 200 ps and the amplitude of a few kilovolts), the proposed biochip adopts grounded coplanar waveguide (GCPW) for a wide working bandwidth, which was fabricated with 160 μm thick electrodes for uniform distribution of psPEF in the cross-section. To ensure that only psPEF is generated in the biological medium containing cells except for ionic current, this work proposes to install capillary tubes in the electrode gaps for electrical insulation and cells delivery. By electrical measurements in the time domain and frequency domain, the exposure system is adapted for local generation of extremely high-intensity psPEF with the 3 dB bandwidth up to 4.2 GHz. Furthermore, biological experiments conducted on the developed exposure system verified its capability to permeabilize biological cells under the exposure of high-intensity psPEF.

Ultrafast control of magnetic interactions via light-driven phonons.

Resonant ultrafast excitation of infrared-active phonons is a powerful technique to control the electronic properties of materials, leading to remarkable phenomena such as light-induced enhancement of superconductivity1,2, switching of ferroelectric polarization3,4 and ultrafast insulator to metal transitions5. Here we show that light-driven phonons can be utilized to coherently manipulate macroscopic magnetic states. Intense mid-infrared electric field pulses, tuned to resonance with a phonon mode of the archetypical antiferromagnet DyFeO3, induce ultrafast and long-living changes of the fundamental exchange interaction between rare-earth orbitals and transition metal spins. Non-thermal lattice control of the magnetic exchange, defining the very stability of the macroscopic magnetic state, allows us to perform picosecond coherent switching between competing antiferromagnetic and weakly ferromagnetic spin orders. Our discovery emphasizes the potential of resonant phonon excitation for the manipulation of ferroic order on ultrafast timescales6.